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David Paterson
12-02-2003, 03:57 PM
I recently built a small electric pot furnace using Kanthal A1. It is about 3 cubic feet on the inside and the pot holds about 100 lbs of glass. So far, I have charged preheated cullet only, and it gives very nice glass.

Up to this point I have used (and still have) an invested pot furnace.

The unit works perfectly, so far. It draws about 4.5 to 5 KW at 2000 F and around 6 KW at 2150.

The elements are around the sides in grooves in insulating firebrick. They are not protected in any way, so I have to be carefull charging.

I would like to melt Spruce Pine, or perhaps another batch, and would like to hear recomendations from anybody melting batch in a similer unit.

Thanks

Ben Rosenfield
12-03-2003, 07:09 AM
Hi David,

You're several steps ahead of me; however, your setup sounds a lot like what I'd like to do. I hope to melt the same amount in an electric, using A1 elements. Perhaps I could e-mail you some time and get some insight into your design?

I wish I could give you feedback from personal experience, but all I can do at this point is link you to threads that may help.

http://talk.craftweb.com/showthread.php?s=&threadid=2065

You might also want to check out http://www.kurtwalrath.com/largeglassstudio/furnace.htm

David Paterson
12-03-2003, 10:40 AM
I am very busy right now with Christmas orders. However once the rush is over, I intend to post pictures and a detailed description of my unit.

Pete VanderLaan
12-03-2003, 10:44 AM
For both of you, please keep this discussion going so that other people can read what you post. There well may be observations from others that will help you both as well. It's the purpose of the board. :dog:

Ben Rosenfield
12-03-2003, 11:26 AM
No sweat. It'd be my pleasure.

And thanks in advance, David.

Richard Huntrods
12-03-2003, 11:27 AM
David,

I've posted about this elsewhere on the board, but this is a good topic.

I recently finished building a small studio (10' by 14') with a 40lb electric wire furnace. The furnace was built according to the plans from Mark Lauckner (Mayne Island Glass). This furnace design is very small (1 cu ft heating chamber, 25" cube outside dimensions).

I too melted cullet, but had a disaster on my first melt, so the furnace is down for repair (details on http://www.huntrods.com under the glassblowing link).

I'm going to melt Spruce Pine batch once the furnace is repaired. There's a lot of people here in Calgary melting Spruce Pine (about 1/2. The rest are using "Seattle Batch"), so there's plenty of expertise locally - although they use gas furnaces.

So - I'm using a very similar setup (but smaller), so once I'm up and running we should compare notes.

Cheers,

-Richard

Steve Stadelman
12-03-2003, 12:50 PM
The whole secret to these melters is low wattage on the elements and solid state controls. Use S.C.R.s or S.S.R.s to power them and keep cullet or batch especially off of the elements.

My 80lb wire job has over 14 months on one set of elements. I have used only cullet and not gone over 2150f because I hate rebuilds. I am using a current limiting S.C.R. and preheat my cullet so it doesn't pop much.

Richard Huntrods
12-03-2003, 01:03 PM
Steve,

Just out of curiousity, how do you preheat your cullet? To what temperature?

-Richard

Randy Kaltenbach
12-03-2003, 02:44 PM
Originally posted by steve stadelman
The whole secret to these melters is low wattage on the elements and solid state controls. Use S.C.R.s or S.S.R.s to power them and keep cullet or batch especially off of the elements.

I have a question about that. What is a reasonable duty cycle for those elements? i.e. is it better to have them continuously cycle on and off quickly (like every second or two) or is it better to let them run for a minute or so? :confused:

Steve Stadelman
12-03-2003, 03:04 PM
I have an answer, the best element life comes with very short (less than a second) switching.

An S.S.R. that swithes every second will not cycle the element temperatures up and down like a mercury relay, so the elements run at a more constant temp and do not get so "shocked".

A burst fired variable time base S.C.R. is your first choice, S.S.R. second, Phase angle S.C.R. third, mechanical or merc relay fourth. The first three give good performance.

Steve Stadelman
12-03-2003, 03:19 PM
Originally posted by Richard Huntrods
Steve,

Just out of curiousity, how do you preheat your cullet? To what temperature?

-Richard

I think I got it from David Williams to preheat in some stainless tubes to 950f in a tiny kiln I got at a garage sale. Sometimes when I don't pay attention I preheat to almost 1200.

Ben Rosenfield
12-03-2003, 04:19 PM
Originally posted by steve stadelman
The whole secret to these melters is low wattage on the elements and solid state controls. Use S.C.R.s or S.S.R.s to power them and keep cullet or batch especially off of the elements.

My 80lb wire job has over 14 months on one set of elements. I have used only cullet and not gone over 2150f because I hate rebuilds. I am using a current limiting S.C.R. and preheat my cullet so it doesn't pop much.

This type of information really inspires me. I know we talked on the phone about me trying to go moly, but damn, if I can get decent life out of wire elements at 2200 F with batch, I'm happy. Not to mention, I would not have the thing running all day, every day. So I think this is a great starting point. I can go moly when my chandeliers are hanging over the canals of Venice ... err ... the muddy creek up the road. Hehe.

Steve Stadelman
12-03-2003, 04:43 PM
There are tradeoffs, you can get started cheap with A-1 wire, but you will be wondering when it is going to fail. A moly system costs more to build but it will have far more reliability and consistently make better glass because you can melt hotter. You are just stringing a wire melter along melting batch. It will crap out, right when you don't want it to.

But like I already said, you can get going on a shoestring.

Randy Kaltenbach
12-03-2003, 04:43 PM
Originally posted by steve stadelman
I have an answer, the best element life comes with very short (less than a second) switching.

An S.S.R. that swithes every second will not cycle the element temperatures up and down like a mercury relay, so the elements run at a more constant temp and do not get so "shocked".

A burst fired variable time base S.C.R. is your first choice, S.S.R. second, Phase angle S.C.R. third, mechanical or merc relay fourth. The first three give good performance.
OK, so short cycles = minimal temp variation of the elements = longer life.

Honestly, this is one reason I love glasswork so much more than many other artforms. I'm both an artsie and a techie at heart (done my time as a professional engineer). Gotta love it! :D

Pete VanderLaan
12-03-2003, 05:01 PM
you're absolutely sure it's not because you have latent masochistic tendencies? :dog:

Richard Huntrods
12-03-2003, 05:40 PM
Geez - you molly minders just won't quit, will you? I get less flack from the gas melters. :D

Sometimes wire is the ONLY way to go.

1. Wire is boatloads of money cheaper to build. Also way simpler (no huge transformers and all that other stuff)
2. Wire furnaces take up way less space than molly rigs. For very small shops, a wire furnace may be all that will fit.
3. For the "weekend warrior" glassblower, I cannot see any scenario short of winning a lottery where Molly would make more sense than wire.

Besides, <cough><cough> This is a "wire furnace" thread. We don't got no molly religion here! :D

Cheers,

-R

Pete VanderLaan
12-03-2003, 06:04 PM
moly furnaces don't take up any extra space and the SCR is not big either. My transformer is outside.

Wire is way cheaper up front, but not in the long run. I can replace an element hot if I have to, try that at home!

Also, I won't have to replace elements often at all. I do tighten things though.

If you are going wire, pay attention to Thumb. He really has this worked out.

I would agree that wire is more approachable than moly but unless you can limit the current, you are in for some long evenings. Use the SCR.

Remember I run both types electric and Gas. I like both and they are very different. :dog:

Jay Holden
12-03-2003, 06:24 PM
- you molly minders just won't quit, will you? I get less flack from the gas melters.. We don't got no molly religion here!


Forgive them Steve, God of Molly, For they know not what they do.

Steve Stadelman
12-03-2003, 06:30 PM
Originally posted by Richard Huntrods
Geez - you molly minders just won't quit, will you? I get less flack from the gas melters. :D

.

Besides, <cough><cough> This is a "wire furnace" thread. We don't got no molly religion here! :D

Cheers,

-R

I'm not trying to give anyone flack bub, I'm just a one trick pony so this is what I yak about.;)

Michael Stevens
12-03-2003, 09:06 PM
I thought we just did this gig. if its wire use cullet hands down.

David Paterson
12-03-2003, 10:53 PM
The reason I started this thread was to get feedback from anyone melting batch in a wire furnace.

So far, I have yet to get a serious response and would still like to hear from anyone melting batch.

In regards to the moly debate, there are a few issues I would comment on.

The inside of my furnace is about 19" across and 15" deep, and I have a 16" diameter pot in it. Seems to be a pretty efficient use of space, and the pot is evenly heated on all sides. Could you do this with moly, or would you need a much larger interior space for the same size crucible to get even heating?

Larger spaces cost more to heat. What would the KW draw be on a moly furnace that would evenly heat a 16" diameter crucible to melt about 100 lbs of glass? Mine idles at 2000F at about 4.5 KW.

Since I am using variable transformers, I believe I have the system that is easiest of all on wire elements. I set an exact output voltage, and the furnace stabilizes at a certain temperature.

It seems to me that 8 monthes to a year on a set of elements is pretty good. I wound my own elements out of 13 guage A1 for about $15.00 each on a bench lathe. They take about 15 minutes each. Cant do that with moly, so what do they cost? Nothing lasts forever. Right now my wire furnace is a secondary furnace, so I intend to shut it down at least a few times per year anyway, and will replace the elements at some point as regular maintenance for the grand total of $60.00.

It seems to me that there is a continual search for "The Best" in technology, when in fact the best is sometimes the simplest.

Steve Stadelman
12-04-2003, 12:13 AM
The size of pot you are talking about would use 4 12" moly's hanging from the crown down, they probably (but not always) should be above the potline, They cost $150.00 each.

The K.W. draw would be 10 (roughly) and the unit would run off of a 50 amp 240 volt breaker.

Yes the variable transformer approach is the best you can do. Yes since this is a secondary unit you can get away with shutting it down whenever you want and yes there are alot of ways to skin a cat.

You CAN melt batch in a wire melter but it will reduce the life of the elements, since you know how to make your own, and can do so cheaply, you are in a really good spot.

Most folks who start this line of queationing are talking about this being their ONLY melter and want to know how it should be done with no knowledge of watt loading, power supplies, or cooking times or temperatures for cullet or batch.

That is O.K. and since we seldom know where a person is in their knowledge base it is really easy to throw out lots of answears and opinions.

All that said, do anything that you can to keep batch and it's dust off of the elements, check out Kurt Walrath's setup, and where is Parker Stafford anyway?

If you keep the temp as low as possible to both fine out the batch in a reasonable time, and keep the elements alive you will do O.K.

I have heard of folks fining out Spruce as low as 2200f your results may vary, and that will take alot of time, I don't know how much.

I have never said that moly is the only way to go, it is not the cure-all to everything and I was just as fascinated as anyone else to hear Hugh Jenkins talk about recuperation. Again, there are alot of ways to skin a cat, but I firmly believe that for the investment, my way is very, very good in the long run.

Richard Huntrods
12-04-2003, 02:00 AM
Originally posted by David Paterson
The reason I started this thread was to get feedback from anyone melting batch in a wire furnace.

So far, I have yet to get a serious response and would still like to hear from anyone melting batch.

...



Actually, you got three good responses right off the bat.

-R

Ben Rosenfield
12-04-2003, 07:50 AM
Would using quartz-encased elements help guard against damage caused by batch? Or would this introduce other issues -- aside from increased cost?

Dave Bross
12-04-2003, 09:13 AM
I'm melting home mixed batch in a wire melter.

The critical thing there is probably the mesh size of the silica. Tom uses 325 mesh in spruce pine and so do I.

See the "virgin batch" thread here about a page back for the particulars.

I'm melting in a 15# furnace that pulls around 10 amps.

Based on Mark Lauckners design it's one 14 gauge 21 ohm element running on 220. A new element from Duralite all wound up and ready to stretch and install is $40. I've been having some crucible failures (see crucible failure threads here)so I don't yet have a handle on how long it will go. I use cheap assay pots for most things and Pete pots for some things that warrant it. The assay pots cost $20 including freight so if an element goes no big loss. If I was to upsize I would still use the assay pots, just more of them. The largest available is around 15 pounds. I don't use a lot of glass, I'm into smaler things, preferably hollow.

More questions? let me know

Pete VanderLaan
12-04-2003, 09:15 AM
Originally posted by Richard Huntrods


Actually, you got three good responses right off the bat.

-R
I agree with Richard, you got plenty of valuable response, mostly qualifying that load limiting is the way to go doing this stuff and then it works. As I said, I run both and electric is slower and weirder, but it comes out fine. In the good old days, which weren't all that good, we simply went out and tried it and had no one to talk to at all. The first wire furnace I ever saw was in 1970. It's nothing new.
:dog:

Dave Bross
12-04-2003, 10:18 AM
Forgot one detail in my post. I'm using an SSR and a digital controller set up to fire it at one second intervals.

The lack of temp swings with the tighter control is supposed to prolong element life 400 times in the case of an SSR and up to 4000 times with SCR control. I'm sure these numbers were achieved somewhere more element friendly than the glass environment but you get the idea.

The best electrical heating stuff I've seen on the web is at Watlow's site and you have to search around for it because they keep moving it. It's called The Watlow Educational Series and has THE BEST explanations of all things resistance heating and control with pros and cons and simplified explanations.

David Paterson
12-04-2003, 11:33 AM
I didnt mean to insult anybody over their responses. I was hoping someone had melted batch for a year in a well designed wire melter and had some insight on element life.

To further the moly debate a little, consider this:

My furnace consists of less than 90 insulating firebrick, 3'' X 4.5" X 9" each, a few bags of insulating castable for the floor, and a few boxes of fibre blanket. Total cost was not a lot more than the $600.00 for 4 moly elements, and that doesnt include the expensive transformers that moly needs.

My furnace draws about 5 KW at 2150F, apparently half of a small moly furnace. The trick is that I have no crown, reducing the interior space to be heated by about 50%. The lid is made of 3" thick IFB mortered together in an angle iron frame, with 1" of fibre on top. The lid rolls back and forth on angle iron channels. I intend to automate it using an air cylinder.

Perhaps you can see where I am going with this: For a similer construction and operating cost, you could run two wire furnaces for the price of one moly furnace. I am not sure at that point that there is any advantage to moly at all. In fact the reverse would seem to be true.

Randy Kaltenbach
12-04-2003, 11:37 AM
Originally posted by Dave Bross
...
The best electrical heating stuff I've seen on the web is at Watlow's site and you have to search around for it because they keep moving it. It's called The Watlow Educational Series and has THE BEST explanations of all things resistance heating and control with pros and cons and simplified explanations.

I found this stuff at http://www.watlow.com/literature/prodtechinfo/index.cfm

Just select "Information Type": Training and Education and you can pick any of the 7 PDF file books.

Steve Stadelman
12-04-2003, 11:51 AM
Originally posted by David Paterson

To further the moly debate a little, consider this:
Perhaps you can see where I am going with this: For a similer construction and operating cost, you could run two wire furnaces for the price of one moly furnace. I am not sure at that point that there is any advantage to moly at all. In fact the reverse would seem to be true.

I don't consider it a debate at all, it's a choice. The first one of these that I built is now over six years old, costs less than $250.00 monthly to run at $.065 KWH and has the origional elements.

The only maintenance it has had is to replace pots.

For short term use or projects etc, I would heartily reccomend a wire melter, I am using one right now because I didn't have the power or money available to build the big moly that is under construction right now, I am looking at the next ten years, and using really good castables, great electronics, high quality componants. When this thing is up and running, I want to blow glass out of it and I know it will make the best quality I can have because it will reach the temps I need every day and it will not have to be torn down until the pot change.

Can you blow lots of glass out of a wire melter? HELL YES! Parker Stafford and Sam Davisson do it all the time, and they know thier maintenance schedules religiously and stick to all the little tricks to make it work.

Ben Rosenfield
12-04-2003, 12:07 PM
Originally posted by David Paterson
For a similer construction and operating cost, you could run two wire furnaces for the price of one moly furnace. I am not sure at that point that there is any advantage to moly at all. In fact the reverse would seem to be true.

According to the temperature ranges Pete listed in the Building Shop Stuff thread (http://talk.craftweb.com/showthread.php?s=&threadid=2065) about melting SP batch, a good melt is 2250, which is about 86.5% of the Kanthal A1's operating maximum. He also cites approx. 2350 to finish the reaction, which is about 88% of the 2552 F max for A1.

And with all the good information here about SCR, SSR, etc., I don't see any reason for a beginner such as myself to go beyond this type of setup. I think this is the most bang for the buck at this point. At the same time, I do see the value in the molybdenum technology, particularly for large melters, or situations for lots of color pots. The setup at http://www.mountainglassworks.com/Studio.html is nice.

Mark Wilson
12-04-2003, 12:38 PM
i have a wire melter, although i melt cullet and not batch. i installed a spare element, that is normally not energized. when an element burns out, i use a volt ohm meter to determine the bad element, and then use the spare element to keep the furnace up until the crucible is empty, then i shut down for service. yes the spare element does age because it is hot, but it does not age anywhere near as fast as a powered element does. this way, i have a way to deal with a burnt element, and save the crucible and the blowing time.

Steve Stadelman
12-04-2003, 12:47 PM
Originally posted by Ben Rosenfield


According to the temperature ranges Pete listed in the Building Shop Stuff thread (http://talk.craftweb.com/showthread.php?s=&threadid=2065) about melting SP batch, a good melt is 2250, which is about 86.5% of the Kanthal A1's operating maximum. He also cites approx. 2350 to finish the reaction, which is about 88% of the 2552 F max for A1.

And with all the good information here about SCR, SSR, etc., I don't see any reason for a beginner such as myself to go beyond this type of setup. I think this is the most bang for the buck at this point. At the same time, I do see the value in the molybdenum technology, particularly for large melters, or situations for lots of color pots. The setup at http://www.mountainglassworks.com/Studio.html is nice.

Yes it is, I talked Matt through building that (the moly part) a couple years ago.

And yes Ben, you can do this on the cheap and learn alot of stuff along the way. You will learn lots of valuable things about electricity and castables, power supplies and glass types.
I am pulling lots of good ornaments out of my wire melter right now. Once again I want to say that there are TONS of options out there to do your glass with, I am just a proponant of moly.

Watlow has a great website like Dave pointed out and all of thier stuff is also available on cd rom. It gives great demonstrations of WHY different power technologies work like they do.

Richard Huntrods
12-04-2003, 01:11 PM
I use a Watlow controller and two digital relays on my wire furnace.

The default settings for the Watlow controller have it powering the elements for a small burst every second or so.

I have both my annealer and furnace running the same controller setups (just different thermocouples), and it works great.

Power consumption is not totally known yet, but I can fire up both and the main 40A breaker does not trip.

My furnace is built according to the Mark Lauckner plans, although I use a different element size and configuration.

The nice thing about Mark's plans is that the element heating chamber is covered - this protects it from the "normal" glass environment.

Just not from spillovers :rolleyes:

I will be melting batch once the furnace is repaired. According to what I've read here (thanks Pete) and what Ben re-iterated just a post or so ago, there's no reason to avoid batch in one of these units.

-Richard

-R

Richard Huntrods
12-04-2003, 01:15 PM
David,

One other thing...

While bringing up my furnace for the first time, I emailed a bunch of people with wire furnaces (made using Mark's plans).

Basically, what I found out so far is everyone I contacted has melted cullet only - not batch. However, this seems to reflect convenience and suppliers rather than any inherent problem with batch.

Since I cannot get cullet readily, and all the gas-furnace people in Calgary melt batch (either Seattle Batch or Spruce Pine), I will use batch (Spruce Pine).


-Richard

Ben Rosenfield
12-04-2003, 01:22 PM
Originally posted by steve stadelman
And yes Ben, you can do this on the cheap and learn alot of stuff along the way. You will learn lots of valuable things about electricity and castables, power supplies and glass types.

That is invaluable at this stage of the game. I don't take this stuff lightly.

Let me thank you again for the help you gave me, and same to everyone else. This type of knowledge base is not as common as it should be. This is a damn fine board.

:toast:

Pete VanderLaan
12-04-2003, 03:28 PM
I don't consider it to be a debate unless it's a debate over whether you can afford a Porsche as opposed to a Ford Taurus.
The Taurus will get you there while the Porsche will get you there effortlessly. The Taurus may break down on the freeway on ramp, and while repairable will cause you to curse at the time. Remember those Moly elements cost more, but they have no known life span unless you break it yourself. :dog:

David Paterson
12-04-2003, 05:46 PM
If someone gave me a porsche, I would sell it and buy a good PU truck, and use the remainder of the money to upgrade my glass studio. A friend of mine had a Ferrari. It went really fast, but otherwise was big and expensive and not practical in any way.

Jay Holden
12-04-2003, 09:00 PM
The setup at http://www.mountainglassworks.com/Studio.html is nice. [/B][/QUOTE]


Man,That setup is sweet. Thanks for sharing it with us.

Rick Sherbert
12-05-2003, 04:53 AM
I see a lot of reference to kilowatts here as a basis for what it costs to run these things. Remember that a kilowatt is just a snapshot in time, an intantainous value. When talking about cost of electricty you must use Kw/Time or kilowatt hours (KwH). Steve and Pete are hip to this.

Just because you see something pulling 23 amps (5Kw at 220 volts) when you measure it doesn't mean it does it all the time.
On off on off right?

Then the cost per KwH varies regionally....

$.02

Rick

Pete VanderLaan
12-05-2003, 08:42 AM
more like 8.1 cents and 7.2 at night.

I look at my montly bill divided by days. :dog:

Dave Bross
12-05-2003, 03:53 PM
One more thing about wire that has seemingly come down as "rule of thumb" from the combined experiences of Thumb, Parker, Sam, and others...

The wire will last a lot longer if you don't go above 2250F.

Pete VanderLaan
12-05-2003, 07:41 PM
well. I think that trying to convince some folks that moly is a better, yet more expensive system than wire is like trying to convince some people that invested crucible melting really is not the way to go. I'll stop trying on the moly like I stopped trying on the crucibles some time back. The issue about 2250 is absolutely true. Most colors just can't sucessfully be melted that cold aside from fluorines. As Dave has discovered, melting unoxidized glasses without fining agents is an absolute bitch under 2250. The moly is unrestricted as to its performance. You just turn it up. I thought it was all about ease of operation. In it's own way it reminds me of the recuperation issue. They take maintenance, and a fair amount of it. I don't think it's much different with element replacement and shutdowns. I don't want to shutdown more than once a year. I could never maintain that time spent on dinking with elements that a wire unit is going to take. My time has simply gotten too valuable. Strip it all away and a small moly melter can be built very reasonably for relatively little output of cash. Matt Bezark sure did it. Mine is just a big assed expensive hulk but I like them that way. :dog:

Ben Rosenfield
12-06-2003, 09:51 AM
I hear what you're saying there, Pete. Another crucial difference is the needs of the full-time -- dare I say professional -- glassblower and the weekend warrior, hobbyist, or the guy who wants to fire up the melter long enough to blow ornaments to sell to coworkers.

The former clearly needs to know the elements will work consistently (and at high temps) and will stand up to the glass. The latter likely has the time to putz around with element changes and other maintenance routines.

I know I just typed a chapter from the Great Book of Duh, but perspective is important.

David Paterson
12-06-2003, 06:01 PM
I have been blowing glass for over 15 years, and I built my wire melter to melt a higher quality of glass than is available in my invested pot furnace. And also occassionally to melt one or more pots of color.

So far the glass quality is amazing from such a cheap and easy to build unit.

With all the talk of 'porsches', 'hobbyists', and 'professionals', nobody has addressed one issue. The United States is involved in two oil wars at present, and the world is running out of cheap oil and gas.

To quote an article from The Guardian in the UK,

"The oil industry is buzzing. On Thursday, the government approved the development of the biggest deposit discovered in British territory for at least 10 years. Everywhere we are told that this is a "huge" find, which dispels the idea that North Sea oil is in terminal decline. You begin to recognise how serious the human predicament has become when you discover that this "huge" new field will supply the world with oil for five and a quarter days.

Every year we use four times as much oil as we find. The petroleum geologist Colin Campbell calculates that global extraction will peak before 2010. In August, the geophysicist Kenneth Deffeyes told New Scientist that he was "99% confident" that the date of maximum global production will be 2004. Even if the optimists are correct, we will be scraping the oil barrel within the lifetimes of most of those who are middle-aged today."

At least a porsche has a relatively small engine, and goes real fast because of good engineering.

My invested pot furnace, which is five years old, still gives good studio quality glass (even with a few one inch or larger cracks in the botton), melts 150 lbs of glass and runs on about 1200 litres of propane a month (about 320 US gallons). I also reheat out of the crown. My friend has a Correll pot furnace that melts about 150 lbs, used entirely for production work, and even with the heat recuperator, it gulps back close to twice as much propane. Frankly, I dont see the logic.

The reason the Correll furnace is more expensive to run is that it is perhaps double the internal volume because of the need to have a lot of space around the pot.

In reality, very few blowers need better glass quality for the bulk of their work than is available in a tank or invested pot furnace.

If you can get at least 8 monthes out of Kanthal A1, and you should shut down to replace the pot in eight monthes, and the elements are really cheap and easy to replace, and it cost HALF as much to run as a moly furnace or a Correll furnace, then I would directly challenge the logic of using these over-designed energy guzzling and EXPENSIVE units.

I am sure that one day not too far off, using thousands of gallons of propane or huge amounts of electricity just to make baubles for rich people will be simply outlawed.

Steve Stadelman
12-06-2003, 06:12 PM
David, I just came back inside for a break from dumping some old mercury relays in an aquifer and I just don't understand why you seem so angry. All of the furnaces that I have either built or helped build are very very efficient.

David Paterson
12-06-2003, 08:09 PM
I am not angry. Sometimes a little exageration helps to make a point.

I have built 6 tank furnaces in my life (3 were invested pot furnaces). And now this wire melter.

If I had known years ago what I know now, I wouldnt have worked nearly as hard to pay the giant gas bills that some of my earlier furnaces sucked up.

For any glassblower that still blows their own glass, big energy bills for that "porsche" simply mean you work harder. North America consumes something like a third of all the worlds energy. Our economy is so closelty tied to oil prices that every run up in oil prices has caused a recession. To work your ass off, instead of life being easier, from the consumption of lots of energy doesnt make a whole lot of sense.

A friend of mine bought a Correll furnace. The price delivered to Canada was about $20,000 Can dollars. I built my wire melter for a little over $1000. I was originally quite impressed with the Correll furnace. The heat recouperator appeared to be almost a stroke of genius. So I was quite surprised at how innefficient it seemed to be compared to a cheap invested pot furnace, or now an even cheaper and safer wire melter.

After you mix yourself a drink from that aquifer, I would challenge you to design a moly furnace that melts 100 lbs of glass and runs on 5 KW per hour instead of 10. It probably is possible.

And further, to find a way around the strange power requirements of moly when first heated that require expensive transformers, perhaps using some type of readily available surplus part.

Pete VanderLaan
12-06-2003, 09:16 PM
well david, you leave out the replacement costs of your elements and you leave out your color bill which for most glassworkers I know starts at about 4000 dollars a year and goes up, and the cost of an assistant to heat it up, or heating it up yourself and losing about 30-50% of your daily productivity doing that instead of gathering the color from the pot.

If you aren't using the SCR for managing your power loading, you will replace a lot of elements. That will still translate into downtime I don't have. My transformer cost 900 bucks and will last the rest of my life. There is no known lifespan on the elements unless you break them yourself. I never have to worry about what I am limited in melting. My furnace gets very hot, way hotter than 2250F which will kill your elements dead and like the energizer bunny just keeps going and going. My electric bill averages 500 a month or so. This is comparable to my gas systems.
I have built wire melters in the past, mostly small ones. They are repair intensive little critters.There is no comparision between the two systems for versatility. It's a question of what you can afford and how much versatility you demand from your furnace. I want a lot.

If you really want to argue about being ecologically sensitive blowing glass is an enormous energy consuming joke on the planet no matter how you do it. No one who blows glass should claim that they are "greener" than someone else.
:dog:

David Paterson
12-07-2003, 12:47 AM
Pete,

I actually agree with you on your last point! I am certainly no "greener" than any other glassblower.

However, I am trying to challenge peoples thinking. The energy bill is often an insignificant part of the overall cost on a large operation, such as Chihuly's, where as in a one person studio, it simply means you have to work harder, often making some trinket, to pay the extra costs.

If the gas bill is $1000 a month instead of $500 (mine is about $500 Can dollars), then the extra $6000 in cost for using a poorly designed furnace is an extra 600 Christmas balls at $10.00 each. Perhaps an extra week of work for no reason.

My first wire furnace was very small, ran on the power of two toasters, and melted three little pots of color. It sat on the floor and the lid rolled back and forth, using garage door rollers, so you could gather easily from the top. The lid worked so well I adapted it to my larger wire furnace.

For me, the point of the wire furnace was to use it to melt larger pots of color on occassion, and to do that at a reasonable cost.

When we live in a culture that consumes about a third of all the worlds energy, while famine is still quite common in the world, it oddly still seems easy to argue for "better" over cheaper, when better glass quality certainly isnt noticed on those extra 600 balls.

By the way, the energizer bunny died recently. That poor little guy who just keeps going and going died from too much sex.

Someone put his batteries in backwards and he just kept coming and coming.

Steve Stadelman
12-07-2003, 01:07 AM
Well, that's what I have been saying, my moly setups run just as cheaply as the wire job that I am currently using, and the first moly one is now six years old.

The initial construction cost is higher, but the attainable temperature and lifespan make up for that.

All along, and in everything that I do I admit readily that there are lots of ways to skin a cat and lots of different needs and budgets.

Pete's uses as much electricity because it is in his words "Big Boned" I prefer to say that it has a "Nice Personality".

My 300lb design uses in the neighborhood of 4-5 mwh per month and my first 100lb invested unit idled when new at 1300 watts, my ex used more electricity on her hair.

Pete VanderLaan
12-07-2003, 08:40 AM
David: Do you use color or don't you? If you do, it was made in an inefficient furnace 4-10,000 miles away and sells for up to 55 dollars a KG. Thta's inefficiency.

I make five gather pieces a lot. If I were to use a 100 lb melter I would charge every day or every other day, and at 2150 if would take forever to fine out. The cost of running a furnace is during the charging time, not the idling time. My electric bill would probably actually be higher than it is with the current moly unit, based on high fires.

Further, pot life is based on the same cycles. Your pot is good for 70-90 cycles and should be replaced, invested or not if you want great glass quality. At my current usage I would pull the pot every two months. That is not attractive.

What works for you is due to your scale of operation, not the genius of the design. :dog:

David Paterson
12-07-2003, 10:38 AM
OK OK!

You guys have almost convinced me to retrofit my wire melter with moly.

So where do you get specs and prices on moly elements?

Pete VanderLaan
12-07-2003, 12:51 PM
I suspect that the way Matt Bezark did his would be similar to your sizing. Steve Stadleman consults on design and also builds the systems. I flew to Portland when I wanted to build one of these things and Steve and Jon Meyers were aces. Steve is the one that showed Kyle Gribskov and Jon how to build these. He walked Matt thru his on the phone. He also was key to Henry Halem in his venture. I flew steve to New Mexico when I was ready to asemble the electrical components of my big boned beauty. He knows where to find all the weird parts, all the cheap parts, and most importantly how and why they work. I cannot recommend anyone as highly as I would Steve. He really knows his stuff. Also he's getting to be too old to remain a fireman.
:dog:

Parker Stafford
12-08-2003, 01:36 AM
I tend to feel that how your furnace is set up will determine how well it performs. How close are the elements to the glass line? Are they above or below the pot? How well are the elements protected if they are below? Watt loading is important. How much dust they will get on them, or popping cullet is a concern and a consideration. Being able to use your eyes and powers of observation are important in a wire melter. Learning to see a dying element a month before it happens is not hard to develop as I do it all the time. Every now and again, something will come along that will f--- it all up, like a long power outage, or bad metal in the wire. I believe this has happened once in the seven years I have had this furnace.

I think that preheating batch is okay if you can also keep the batch wet, which gets to be tricky when you go up to around 900 degrees or so. I used to preheat, and it did help with speeding up the melt, but since my elements are above the pot, I was getting dusting, and this was not good for the elements. No free lunch. You gain in one area, lose in another. I am not about to step into the sweet smelling mess that is the moly/wire debate. Do what works for you in your situation. When it no longer works, cast about for something new. The bottom line is that you enjoy it and are able to make good work. If any of those is off, something needs fixing. If your furnace is giving you trouble, maybe it is design related, maybe it is time for something new.

You can melt batch pretty cool, but you need more time. You can also melt it hotter, but you might lose a little on wire life. Take your pick. I know a guy who never turns his wire unit up to charge temp. He owns a flat glass business and 80% of his business is doing large plate for restaurants, custom installs, etc., so he can charge after using up a pot, then come back to it a number of days later. Says if he has enough time, the glass is perfect. He also gets real good element life.

I find that the best squeeze comes from a drop to 1900 degrees IN MY UNIT. If I do a drop to 2000, I need an extra day for it so sit (again, in my unit)in order to get paperweight quality glass (the bar is lower for some blown things), and have done it like this when I went off for the day knowing I would not be blowing.

Electric will always tend to be more bubbly in my opinion as a result of the atmosphere. It is regular earth atmosphere, not a mix of hydrocarbons being combusted. So take that into consideration Actually, batch is ALL I melt, and I do the melt starting at 2280. I go up to that, and I charge about 50 lbs at first in a 130# capacity crucible. No preheating the batch, and no strict adherence to a 30# only charge size. Then I drop the temp down to 2220 and do the middle charges at that temp. Then before I do the last charge, I ramp back up to 2260-80 and let it soak there for about 4-7 hours (after the charge), although I might go longer if I have the time. If I had more time I might keep the temp down around 2230-50. I keep my high temps in short duration, but I believe in them for getting gasses to expand for fining. I like to have a six hour squeeze before turning up to work temp. If your unit takes a while to drop in temp, like mine does, you need to take that into consideration for the tail end of your "melt" which is your squeeze. Early on I realized that it took my furnace about 5 hours to drop from charge temp to squeeze temps., and when I adjusted the melt to take that into consideration (for the time actually spent at around 1900 F.), the glass quality got much better. I was going in the evening to turn the furnace down, and often it was late enough that the unit did not have enough time to get a good squeeze in before the a.m..

How careful I am about the melt depends on what I am making. If I am doing solid, I am very anal about how I do the melt. I also stir the glass with a spud as it is the most convenient way to mix the glass in my opinion and get very good evenly mixed glass of top quality. I once saw a guy mixing his melt using a punty attached to a drill. I tried this, and found it to be a big pain in the ass (this was a big studio). It actually got more bubbles in while not really mixing as well as I would have liked. Do the mix at a high temp so you get some real life agitation. I am talking in the 2220+ range. Hotter the better, in my humble opinion, as the glass mixes so much more readily. The glass comes out much better, even when you have a crucible in good shape. When the crucible is in bad shape, you are kind of trying to make a purse from a sow's ear. Sometimes it can work.

Parker S.

David Paterson
12-08-2003, 10:16 AM
Thanks to Parker and everybody else who took the time to reply to my questions.

-David Paterson

David Williams
12-08-2003, 11:30 AM
Originally posted by Richard Huntrods
Geez - you molly minders just won't quit, will you? I get less flack from the gas melters. :D

Sometimes wire is the ONLY way to go.

1. Wire is boatloads of money cheaper to build. Also way simpler (no huge transformers and all that other stuff)
2. Wire furnaces take up way less space than molly rigs. For very small shops, a wire furnace may be all that will fit.
3. For the "weekend warrior" glassblower, I cannot see any scenario short of winning a lottery where Molly would make more sense than wire.

Besides, <cough><cough> This is a "wire furnace" thread. We don't got no molly religion here! :D

Cheers,

-R

Hiya Richard, I think the reason moly comes up in these threads isn't because anyone is trying to sell you, its just the far better and believe it or not, cheaper way to go. I know its hard to hear that because the allure of getting a studio up on the cheap is so strong. Believe me I know. No one could steer me away from building a wire furnace, I had to find out for myself. But if you're a smart cookie you'll listen, and save your money and build a moly. I wish I had made that decision before I built my wire furnace. Its really not so much more expensive. All the refractories have to be purchased anyway, and the controller. The extra money is in the electronics--the transformer and scr. The elements cost a bit more in the short term, but averaged over the life of your furnace the cost of moly elements will be FAR less. Plus, if you are a weekend warrior the moly elements can handle frequent cycling up and down where wire won't. Hey buddy I'm just saying it to help you out, take it or leave it.

Richard Huntrods
12-08-2003, 04:06 PM
Hmmm.

What do you mean by SCR? Do you mean a straight "digital relay" or something more exotic?

Also, what type of transformer is required - can you give me a rough idea of the current and the primary and secondary voltages? I realize there's a whack of design involved, but I'm just looking ballpark (i.e. 20-50 amps 240V primary xxxV secondary is quite different than say a Neon transformer).

How do people normally place the moly elements, and how many are normally used? Again, I know this is part of the design, but are we talking 2 elements, 4 or 6 for a small (< 100lbs) furnace?

Finally, is there a standard size moly element?

The thing is, this furnace is already built. I'm using digital relays + a Watlow controller. The furnace has a 1 cu ft. heating chamber, 40lb crucible. Would molly even fit in this little puppy, or are we talking a whole new furnace?

Thanks,

-R

David Paterson
12-08-2003, 04:08 PM
David,

Where did you buy your moly elements?

Thanks in advance.

David Williams
12-08-2003, 04:47 PM
Originally posted by Richard Huntrods
Hmmm.

What do you mean by SCR? Do you mean a straight "digital relay" or something more exotic?

Also, what type of transformer is required - can you give me a rough idea of the current and the primary and secondary voltages? I realize there's a whack of design involved, but I'm just looking ballpark (i.e. 20-50 amps 240V primary xxxV secondary is quite different than say a Neon transformer).

How do people normally place the moly elements, and how many are normally used? Again, I know this is part of the design, but are we talking 2 elements, 4 or 6 for a small (< 100lbs) furnace?

Finally, is there a standard size moly element?

The thing is, this furnace is already built. I'm using digital relays + a Watlow controller. The furnace has a 1 cu ft. heating chamber, 40lb crucible. Would molly even fit in this little puppy, or are we talking a whole new furnace?

Thanks,

-R

No one should mistake me for a moly expert. SCR stands for silicon controlled rectifier which is a fairly common piece of electronics. What you should do is search the archives where there is tons of info on this. Study up, and come back and ask Steve what you need to know.

Pete VanderLaan
12-08-2003, 05:13 PM
you can learn it on your own but I think you are better off hiring Steve as a consultant. There's a peculiar stage where people want to get something for nothing and I suppose it's human nature. It happens with me and people calling about glass chemistry all of the time.

I had finally matured enough when I needed to know about Moly's that I just bit the bullet and bought the plane tickets to Oregon. That was a risk. By the time I was paying to fly Steve to New Mexico, it wasn't a risk at all anymore.Before that, I had been promised a reasonable moly system for over a year by someone else. Push came to shove and they couldn't/wouldn't deliver. That furnace that Steve showed me how to wire would have involved my making tons of critical mistakes, and the acquired knowledge will be with me for a lifetime. I do the same thing with the color. If people really want to know how to do it, they pay me 1500 bucks and spend the work week with me being overwhelmed. Steve is paying me to take that course in three weeks. :dog:

David Williams
12-08-2003, 05:58 PM
But, I don't think its all that much more complicated than wiring your average control system with a relay and a safety circuit. I think with some experience building control systems and a bit of help from experts like Steve it is easily doable on your own. Easier if you can fly in your expert. The theoretical part is harder. Understanding the interplay between the scr and the transformer has always been difficult for me, and I let that fear rule out a moly furnace for a long time. But Steves lecture notes made it a bit easier, along with the realization that I don't need to understand every last theoretical detail of how it works to feel comfortable with it in my studio. I think I had that epiphany when I was up at Bills who is a great gadget guy and inventor, and I asked him some esoteric question about the moly and he just shrugged his shoulders. I figured if he could live with that, I could too.

Ps. Take it all with a grain of salt, I may be eating my words. I'm going to pick up my moly furnace castings etc in Portland over the holidays and start building it when I get back. Meantime I'm still nursing the wire. Which by the way should be for sale in the spring.

David Paterson
12-08-2003, 10:13 PM
Of all the proponents of moly, no one has yet posted even one supplier, or a website that gives technical details about how they work, or other specifications such as size, configuration, cost, etc.

I know there is a degree of complexity to them, but basic information is necessary to even make a decision that you would like to use them for a particular application.

I also dont believe that it is rocket science, just more complicated than most other electrical configurations that most of us work with.

If george bush can run the country, surely all of us on this board can understand at least the basics of the design that these things require.

Richard Huntrods
12-09-2003, 12:21 AM
David Williams,

Thank you for answering the question about SCR. That's what I thought it was, but I wanted to be sure.

David Patterson,

I agree with you 100%. I'm just looking for information myself.


-Richard

Steve Stadelman
12-09-2003, 12:28 AM
Use the search engine on this site, I have written lots of stuff in the past that details all of this stuff. As to suppliers, I am importing moly's, Or I squared R makes them domestically or Kanthal corp.

Check the archives.

P.S. my favorite supplier of electrical components is Watlow. Excellent customer support and technical assistance.

David Williams
12-09-2003, 02:24 AM
Some of you guys with wire and thinking to upgrade might also consider the path I took. What I did was, to get more life out of my wire elements I got a phase angle scr with a current limit which allowed me to dial down the watt loading on the wire, but also will be rquired for my moly system. I forget what I got it for but its in the archives because I remember talking about it. I think it was like 500$. It was from TTI global which I get all my control stuff from because I have a good relationship with them and they have great support and prices. Well it turned out after that we found out actually a zero burst crossing whozit scr was better for wire. But, to my untrained electrical mind it seems like the current limit is really the key to reducing the watt loading. In fact, I think if you got just a controller with percentage-wise output control (pxr3 129$) and cut down the output signal to an ssr you'd do just as well (with wire) but thats another thread. Anyway The phase angle scr is good for both systems and serves as sort of a bridge to the moly. As far as David Patterson what you asked about suppliers, schematics, etc. Its a relatively new method for melting in the studio and you have to sniff around to educate yourself. I think you'll find most of what you'll need to know in the archives here. I can't imagine that you'd find any richer single source of information for non-engineers outside of Steve's skull.

Brian Blanthorn
12-09-2003, 05:23 AM
Originally posted by David Paterson
Of all the proponents of moly, no one has yet posted even one supplier, or a website that gives technical details about how they work, or other specifications such as size, configuration, cost, etc.

I know there is a degree of complexity to them, but basic information is necessary to even make a decision that you would like to use them for a particular application.

I also dont believe that it is rocket science, just more complicated than most other electrical configurations that most of us work with.

If george bush can run the country, surely all of us on this board can understand at least the basics of the design that these things require.

I put up a molly link to a mag article

I diddent understand it I hate all this elecrtical chat

But the link was well recived by those that know

Was pos about 3 - 5 weeks ago

:sheep:

Pete VanderLaan
12-09-2003, 07:03 AM
[QUOTE]Originally posted by David Paterson
[B]Of all the proponents of moly, no one has yet posted even one supplier, or a website that gives technical details about how they work, or other specifications such as size, configuration, cost, etc.

That is simply totally untrue. This site probably has more nuts and bolts information about suppliers, theory and operation than anywhere I have seen. I suggest that you next say that this site has never posted any information about suppliers for color glass making. Use the archives. :dog:

Richard Huntrods
12-09-2003, 12:45 PM
Pete and Steve are correct.

The archives topics don't always tell the whole story, but there's some great info in them if you just read through the threads.

Steve referred me to the archives, and I looked. There were two web references in those posts that summarize the info on Moly very well:

http://www.theglazine.com/features/molybdenum.html

for a good overall article, and

http://www.chromalox.com/

For total information on the control systems.

This manual answered all my questions on SCRs and power requirements for Moly:

http://www.chromalox.com/manuals/trainingmanuals/

Excellent stuff in those archives (and in the web sites they pointed me to)

I must admit, Moly sounds pretty fantastic. Expensive, but fantastic.

But... I still gotta fix my wire furnace and melt me some Spruce Pine batch! (just getting back on the thread topic, there...) :thumb:

-Richard

Pete VanderLaan
12-09-2003, 03:00 PM
There is also a photo thread I took in Portland in "photos of studio stuff" called "to hell with the portland vase. :dog:

David Paterson
12-09-2003, 04:25 PM
Richard,

Thanks very much. I didnt search the archives because I follow this board quite closely and didnt recall the thread.

I agree that moly seems fantastic in many ways. A quick search on the internet for molybdenum elements from china turned up two sources that would obviously be cheaper than US based products.

When I designed my wire melter a year ago, I looked into both moly and silicon carbide enough to realize that they were too complicated design wise for my purposes. Also expensive in that I wasnt aware of the China option.

I agree with Pete that everyone's situation is different. I dont presently melt my own color, although I used to melt a few pots of color in a small wire melter. Now, I design a lot of my work to minimize the intensive use of color, and show the brilliance of the clear glass. I also use a lot of lustres and metallics on my work, which are surprisingly cheap.

One thing I think that most people dont pay enough attention to is the energy consumption of their furnaces, in at least some cases that I am personally familiar with. A friend of mine, a woman, bought a Correll pot furnace, because she "didnt want to be a furnace builder", even though she had seen me build two invested pot furnaces (typically, they take 2 days of work). Now she works a few extra weeks a year doing production work, compared to me, just to pay the extra costs. I usually go to the Carribean with the money I save for the same length of time. And she never uses the theoretically better glass quality that is available in her $20,000 Can dollar setup.

Matt Bezark
12-09-2003, 09:29 PM
Originally posted by Pete VanderLaan
No one who blows glass should claim that they are "greener" than someone else.
:dog:

i just found out that for $250 more per month i can run my furnace and annealers on %100 wind sourced electricity. how about that!!

matt.

David Paterson
12-10-2003, 12:18 AM
Just imagine if you could catch a small amount of the wind that this discussion board occassionally generates!

Richard Huntrods
01-11-2004, 05:49 PM
David,

OK - I'm now melting Spruce Pine batch in my wire furnace.

I ramped the furnace up to 2150 at 100F/hour (with a couple of hours wait at 900, 1000 and 1100 due to the quartz inversion).

Once the crucible was at 2150, I started ladelling in the batch - about 15-20% of the crucible volume at a time. I let each fill start melting down for about 2 hours before adding more.

I'm currently sitting at about 1/2 full on my 40lb. crucible. (4pm, 1/11/2004)

Reading prior posts, Dave Bross melts homemade batch (if I read Dave's posts correctly) in his wire furnace. He fills at 2050 and then cooks at 2250.

Likewise, I'm going to cook at 2250. I just haven't decided whether or not to fill the crucible full at 2150 first, or start cooking when it's half full.

(remembrances of my first disaster with a full crucible).

-Richard

Dave Bross
01-11-2004, 06:59 PM
Get it full at the lower temp. and then cook it at the higher temp.

You can add more batch as soon as the stuff you added before has gone flat, and is looking sort of like foam. You don't want to pile cold batch on top of unmelted batch. It's also a good idea to let the furnace recover temp. before adding more batch. That all happens about the same time in mine but that may be different in another melter.

You will be making a number of smaller batch additions at the end to get it up close to the rim.

The idea behind charging at a lower temp and then upping the temp to cook it is so that all the sand is dissolved and not making more bubbles for you to deal with while you're cooking it at the higher temp. As long as sand is dissolving there will be bubbles forming.
The fining agents like antimony decompose and produce gasses at the higher temp which cause the bubbles to swell and rise much more quickly than they would otherwise. The antimony also helps by sucking the really tiny bubbles back into solution in the glass as the glass cools on the squeeze below the point where the antimony changes valence around 2150F.

You may need to batch at a higher temp. with Spruce Pine. I've never used it so I don't really know, but I know it's made with fine mesh silica so I suspect it will do just fine at the temps. suggested. If you get silica snots and stones in the finished glass you'll need to batch at a higher temp.


I looked up Frank Woolley's comments on all this in "glass Technology for the Studio", which you can get from Whitehouse books for about $12. He says as long as you are batching at least 50 degrees below the temp. where you will be cooking you're OK. Frank was a Corning Glass engineer who wrote that little book to help studio glass artists.

Richard Huntrods
01-11-2004, 07:09 PM
Originally posted by Dave Bross
Get it full at the lower temp. and then cook it at the higher temp.

You can add more batch as soon as the stuff you added before has gone flat, and is looking sort of like foam.


Excellent dexcription! That's exactly what I'm seeing right now. I've added 3 rounds of batch so far, and the crucible is just over 1/2 full of "flat foam". I just added another run of batch, so it's sitting at 3/4 full - mixed batch and foam (as of this minute). Still all at 2150F

You don't want to pile cold batch on top of unmelted batch. It's also a good idea to let the furnace recover temp. before adding more batch. That all happens about the same time in mine but that may be different in another melter.


Again, that's what I've been doing. My furnace drops from 2150 to between 2132 and 2140 during additions (I also keep looking :rolleyes: )

It seems to take about 5-10 minutes to recover the temp, and I've been waiting 1.5 to 2 hours between additions (no reason, it just works out that way).

You will be making a number of smaller batch additions at the end to get it up close to the rim.

The idea behind charging at a lower temp and then upping the temp to cook it is so that all the sand is dissolved and not making more bubbles for you to deal with while you're cooking it at the higher temp. As long as sand is dissolving there will be bubbles forming.

Sounds good.

The fining agents like antimony decompose and produce gasses at the higher temp which cause the bubbles to swell and rise much more quickly than they would otherwise. The antimony also helps by sucking the really tiny bubbles back into solution in the glass as the glass cools on the squeeze below the point where the antimony changes valence around 2150F.

You may need to batch at a higher temp. with Spruce Pine. I've never used it so I don't really know, but I know it's made with fine mesh silica so I suspect it will do just fine at the temps. suggested. If you get silica snots and stones in the finished glass you'll need to batch at a higher temp.

Again, sounds good. I'll be anxious to see what this glass looks like when done. I know from SP cullet that this furnace will produce a very nice glass with a 1900 squeeze and 2150 working temp.

This time I'm going to play with working temp a bit - see what 2050 is like and all that.

Another question (If you've ever done this). If I finish charging later tonight, what about letting it sit at 2150 (charging temp) overnight, and then cooking it tomorrow?

I looked up Frank Woolley's comments on all this in "glass Technology for the Studio", which you can get from Whitehouse books for about $12. He says as long as you are batching at least 50 degrees below the temp. where you will be cooking you're OK. Frank was a Corning Glass engineer who wrote that little book to help studio glass artists.

Thanks,

-RIchard

Dave Bross
01-12-2004, 09:08 AM
I don't think it would hurt anything. There have been a number of posts about folks forgetting to turn up the furnace after batching and getting good glass anyway.

Personally I've always tried to get my cook time scheduled so that it happens while I'm asleep and I can then squeeze it in the morning and have glass that day.

Richard Huntrods
01-12-2004, 10:13 AM
At 11pm last night, the most recent charge had not melted, so I just left it overnight.

This AM at 8:30, the glass had melted down flat again - to less than 3/4 of the pot. I did another charge, and will let that melt.

Once I'm over 3/4 of the pot "melted flat", I'm going to turn it up to 2250 for cooking. Probably around noon, unless another charge is required.

I see no need to fight for "a totally full" crucible on this first charge. Anything over 3/4 full will give me plenty of glass for this first run of the system.

Now all I need is a gas "bar-b-que" fitting installed in the house to use instead of those 20lb propane bottles, and I'd be set!

-Richard

Ben Rosenfield
01-12-2004, 11:43 AM
Congrats, Richard. :toast:

Sounds like you're up and running quite nicely again! :strong:

Richard Huntrods
01-12-2004, 12:03 PM
It's not time to celebrate yet. I've been here before without incident.

Last time the problem came when I heated to 2400 because the cullet wasn't behaving as expected. I now know the real problem was "mass-temp lag". That is, the heating chamber said 2200, but the center mass of the cullet was nowhere near that.

This time I started with an empty crucible at 2150 (heated 100F per hour). Due to the way this furnace behaves (learmed while empying out after the disaster), using the ramp function pretty much guarantees accurate temp in the heating chamber and in the crucible.

I'm still melting down the charges at 2150. The batch is melting down very nicely to flat between charges. I'm not making the mistake of charging too soon, either (almost did that at 10:30 am today, but then I thought better of it). I still have at least one more charge before I cook the glass at 2250.

It looks like I'll start the cooking this evening, and let it go all night. I want to start early enough that I can monitor the cook to catch/avoid any problems.

Once it's cooked and I start the squeeze - THEN I can celebrate!!! I have a bottle of Guinnis waiting...

:toast:

-Richard

Randy Kaltenbach
01-12-2004, 01:51 PM
Originally posted by Richard Huntrods

Once it's cooked and I start the squeeze - THEN I can celebrate!!! I have a bottle of Guinnis waiting...

:toast:

-Richard
I watch this with great anticipation! (or as Dr. Frank N. Furter said with "antici...pa...tion" :D ).
With a bit of luck I'll be invited over to see this rebirth! If all goes well, we won't even set each other on fire in the confines of the tin shack :D .
I've also discovered that if I bring beer into a studio I am made to feel very welcome.
:toast:
- Randy

Richard Huntrods
01-12-2004, 02:09 PM
Yes. Beer good. Cold bad.

:toast: :toast:

-Richard

Richard Huntrods
01-12-2004, 04:39 PM
Okay, then.

New pictures of the rebuilt furnace and current Spruce Pine batch charging are now up on my web site:

http://www.huntrods.com/

under the glassblowing link.

Yes, that's me in shorts - in January - in Calgary Alberta - in the snow! Thank goodness for Chinooks - it's currently -2 C or 17F here.

Thought I'd inlude that for all you "warmer weather" glassblowers. By the way, temps between -5 and +5 Celcius are perfect for glassblowing in my shack - the glory hole becomes a wonderful space heater! :-)

Cheers,

-Richard

Ben Rosenfield
01-12-2004, 06:30 PM
Sorry to get tangential, but to celebrate, try some of this:

http://www.vansteenberge.com/Bodypages/engels/beer/EBgiftpacks/EBGuldenDraak.html

Randy Kaltenbach
01-12-2004, 06:56 PM
Originally posted by Richard Huntrods
...Thank goodness for Chinooks - it's currently -2 C or 17F here...

Cheers,

-Richard
1. A Chinook is a warm wind (like a Santa Ana for you Californians; like a Sirocco for you Italians, etc.)
2. errrrr - check your math, Richard. Have you already been "celebrating"? :toast:

- Randy

Richard Huntrods
01-12-2004, 10:12 PM
Darned conversion software.

-2C = 28.4F

Even warmer!

-R

Richard Huntrods
01-13-2004, 01:18 AM
Apologies in advance for the long post, but I think this should prove interesting...

Current charging (SP batch):

It's just after midnight, January 13, 2004 and I *KNOW* what destroyed my last furnace.

I charged my rebuilt furnace at 2150 all day today. By 7:30 pm, I had a nice flat layer of melted glass sitting between 1 1/2 and 1 1/4 inches from the top of the crucible.

At 7:30 I started the cooking process by raising the temperature to 2250F. My plan was/is to cook the glass overnight, followed by a squeeze to 1900 tomorrow morning.

Being cautious (because of the past disaster), I decided to check the glass every hour or so. This is because the furnace will take 1 hour to rise from 2150 to 2250, but the "glass mass" will take longer to reach the new temperature.

At 9:30, I did my first check. The glass was now definitely higher in the crucible - about 3/4 inch below the top.

I checked again at 10pm. The glass was now 1/2 inch from the top.

Why? Thermal expansion. Checking with a punty, the layer of bubbles was not all that thick (and didn't increase in size between 9:30 and 10pm), but the glass had expanded due to the increased temperature.

Using the punty, I gathered some of the bubbles until the level was again 1" below top.

Between 10pm and now (midnight), I've checked every 15-30 minutes, and gathered bubbles three times more. Once (10:45) the glass was 1/4 inch from the top. Again, the thickness of bubbles was NOT the reason (I checked with the punty) - glass expansion was the cause.

The temperature now appears to be at equilibrium in the glass mass - recovery time after a gather has decreased from 5 minutes to about 30 seconds, and the temperature drop has lessened (at 9:30 a gather dropped the temp to 2239, at midnight a gather dropped the temp to only 2248). The level appears stable at 1 inch below the top of the crucible.

I'll check again in an hour, but it looks like I can let it cook overnight now.

SO what killed the first furnace?

SO - what destroyed the first furnace build? Same thing - thermal expansion. That time, I filled the crucible to the brim with cullet, let it melt, and filled it again. When I observed the "stiff foam" (my words from back then), it was about 1/2" to 3/4" below the lip of the crucible. SInce the cullet didn't seem to be very melted, I bumped the temp from 2200F (melting temp) to 2400 F, starting at noon. At 2pm, all was fine. At 5pm, the glass had overflowed. I know know that the expansion would easily have caused the glass to rise more than the 3/4 inch that I had, and so the glass simply had to overflow.

WHY? This is a straight-walled crucible, not a round crucible. Round bottom crucibles increase in diameter as you move up in height, so the expanding glass has "somewhere to go" (the extra diameter). In a cylindrical crucible, the glass can only rise.

In the final analysis, it wasn't a faulty thermocouple, or bad cullet, or foam or crap falling into the crucible - just plain old thermodynamics.

Anyway, this is what I have, and what I've found. I'll live with this crucible and furnace for the next little while, as that's what I have (and it's hot). Later, I might put a round pot into it.

So - if the furnace survives the night, I should have some nice glass by Wednesday morning!

-Richard

Pete VanderLaan
01-13-2004, 07:33 AM
I think it's worth noting that we normally talk about a glass having a linear expansion of 90 or 96. What never gets thought about is that this is in ten thousandths and is only measured up to 300C. The fact is that the expansion keeps on going when you pass 300C as Richard has observed. It actually really adds up. I find a pot that is brimfull at 2350 will shrink about 3/4 of an inch being brought back to 2050F. :dog:

Richard Huntrods
01-13-2004, 10:26 AM
Originally posted by Pete VanderLaan
I think it's worth noting that we normally talk about a glass having a linear expansion of 90 or 96. What never gets thought about is that this is in ten thousandths and is only measured up to 300C. The fact is that the expansion keeps on going when you pass 300C as Richard has observed. It actually really adds up. I find a pot that is brimfull at 2350 will shrink about 3/4 of an inch being brought back to 2050F. :dog:

Absolutley!

Also, some of the expansion is also due to the entrained air bubbles (seeds) in the melt expanding as you heat the glass from 2150 to 2250. I monitored the furnace during the night, and by 8:30 am the glass level had dropped 1/4 inch - and the bubbles were fewer and larger.

Pete - how do you tell when the glass is "cooked" and ready to squeeze?

When I started cooking, there was a stiff froth of bubbles about 1/4 to 1/2 inch thick on the surface. When I say froth I mean the bubbles were less than 1/8 inch in size, and plentiful.

It took 5 hours in my furnace for the entire glass mass to heat from 2150 to 2250, so it cooked at 2250 from 1am to now (currently 9:30). At 8:30 the bubbles were fewer, a thinner layer (less than 1/4 inch) and larger (most between 1/8 inch and 1/4 inch).

I can happily cook till noon, supper, evening or midnight (or longer)- but there's no point cooking longer than necessary, IMO.

What are the key indicators that glass is ready for the squeeze?

-Richard

Richard Huntrods
01-13-2004, 03:50 PM
I think I may have an answer to my own question. I cooked the spruce pine batch for 12 hours at 2250 last night (not including 5 hours to get the temperature at 2250 throughout the pot).

At noon today the glass was relatively clear on top (no significant bubbles), so II gathered a sample. It was full of bubbles (as expected), but they were uniformly distributed throughout the sample, and all were "pinhead" sized.

So - I started the squeeze. (it will be at 1920F).

Looks like this process worked almost perfectly!

The 40lb crucible took almost a full bag of Spruce Pine batch (50lbs), but since it's about 20% water, this is right. I could have put it all in the crucible - but then I'd have been scooping glass out last night. As it is, I had about 1/4 of a large peanut butter container left over. Next time I think I'll reserve a whole peanut butter container aside to prevent the expansion from getting near the lip.

One other thing abou SP batch - I added batch at room temp (-2 C or 28F) to the crucible which was at 2150F. There was an initial "foosh" as the batch hit the crucible (or melted glass), but no popping or any other unpleasant side effects. A VERY NICE batch to work with!

Now - tomorrow night - the big test. The first official "blow down" of the Tin Shack Studios!

I took some pictures of the first two gathers (at 2250, before the squeeze) to show how it looked. Again, on my web site.

-Richard

Pete VanderLaan
01-13-2004, 03:51 PM
The bubbles grow larger and are spaced further apart and there is good clarity between the bubbles. You described it perfectly. :dog:

Richard Huntrods
01-13-2004, 04:12 PM
Thanks Pete. I do appreciate the encouragement.

Boy it sure feels good to have success!

This process was exceedingly rewarding. I can see why making your own batch is the next logical step!

-Richard

Richard Huntrods
01-15-2004, 04:05 PM
The glass finished cooking and squeezing, so last night I had the first ever Tin Shack Invitational Blowdown...

Allan Gott, Randy Kaltenbach and I spent from about 7:30 to midnight blowing beer mugs and other vessles with the first glass from my furnace. If you're interested, pictures and blab are on the website...

http://www.huntrods.com/ under the glassblowing link.

As for the glass, it is *perfect*. Crystal clear, no bubbles, cords, seeds, etc. Came out of the annealer looking fantastic!

In keeping with the topic of this thread, my next post will be a detailed description of my process for making Spruce Pine batch in my wire furnace.

-Richard

Richard Huntrods
01-15-2004, 04:17 PM
WARNING! LONG POST!

Also - I'm no expert (having only done one batch to date, but I figured "this is really fresh in my mind", so ...

Here are my batch cooking instructions for Spruce Pine (87) Batch using my 40lb wire furnace:

NOTE: since this was the first batch run since the rebuild, the crucible started totally empty at about 27F. Subsequent charges will start with a non-empty crucible at 1919F (my "squeeze and hold" temperature) A non-empty crucible will have anywhere from 1" of glass to 1/2 full depending on what I need and when.

1. The crucible is heated to 2150F. This was done using the ramp function (to preserve elements) of 100F/hour.

2. Once the crucible has equilibrated at 2150F (say 2-3 hours), batch charging begins.

Batch is added such that about 1/4 of the crucible volume is added at one time.

Temperature should initially drop almost 20F after an addition, but as the crucible fills this will change to a drop of maybe 2 degrees F (as the glass mass increases and equilibrates at 2150).

Temperature recovery times will also decrease as the crucible fills, from maybe 10 minutes to under 30 seconds.

Once a charge of batch has been added, the furnace is left for between 2 to 2 1/2 hours to allow the batch to melt flat. Under no circumstances should batch be added until the previous charge is melted totally flat. It should look like slightly foamy glass - it should NOT look like raw batch at all.

The crucible should be filled NOT FULL. I found for a cylindrical crucible that 1 1/2 inches below the rim is more than enough. Any higher and the cooking process (heat) will cause the glass to expand and overflow. This is, of course, very crucible dependant. Larger crucibles with non-vertical sides have much more leeway than the small vertical pots.

3. Crucible is filled and the glass is flat - time to cook. I heated the glass from 2150 F (charging temp) to 2250F, again using my 100F/hour ramp function on the controller (Watlow).

In my furnace, it takes about 4 to 4 1/2 hours for the entire 40lb pot of glass to fully equilibrate at the new temperature. This can be checked by peeking at the glass. If the temperature drops more that 2-3 degrees F and/or takes more than about 30 seconds to recover, you are not at equilibrium.

Once at equilibrium, I let the glass cook at 2250 for an additional 12 hours. After 10 hours, you can check the glass to see if it's "done". I use two tests to determine the "done-ness" of my glass. First, a visual inspection should show a very even glass mass, consisting of very fine bubbles (pinhead sized). Second, I take a gather of this glass - the glass should be easy to gather, and the gather should have an even distribution of many pinhead sized bubbles. Other than the bubbles, the glass should appear "clear".

NOTE: I cannot stress enough the value of SSR's and a good controller with a ramp function. Although you don't "blast" the temperature up as fast, you preserve the elements because you are always raising the temperature by small increments, allowing the controller and SSR to give small "bursts" of power to the elements instead of one large-amperage blast. This helps preserve the elements.

4. WHen the glass is done, I squeeze it by quickly cooling the furnace (ramp turned off) to 1919F and leaving it overnight (at least 12 hours). Resist the urge to peek at the glass once the temperature drops below 2200F, as this will chill the surface of the glass. Just leave it.

5. Once the glass has been at 1919F for 12 hours, you can bring it up to working temperature, or let it sit until you need it. For me, working temperature is 2070F. At that temp, the glass was easy to gather, but not "watery". This is somewhat of a personal choice - you want the glass at a temperature that produces nice gathers, but still hot enough that any trails quickly melt away from the punty (as you rotate it on the pipe stand near the crucible).

6. After your blowing session is complete, you can either heat the crucible to 2150F to start charging again, or cool it to 1919F to hold it for another day (depending on the amount left and what you need).

FINAL NOTES: If you are going to shut off the furnace, then you must gather as much glass out of the crucible as possible. I've found with the cylindrical crucibles you can get all but about 1/8 inch out of the pot with a small amount of care. This will cool and reheat without problems (again, I use the ramp at 100F/hr for shutdown and startup). When starting from room temp, I also stop the heating at 900F, 1000F and 1100F for 2 hours each temperature to ease through the quartz inversion.

I've also heard of people "idling" the furnace at 1600F without problems. For now, I'm going to stick with 1919F.

Cheers,

-Richard

Randy Kaltenbach
01-15-2004, 04:47 PM
Originally posted by Richard Huntrods
The glass finished cooking and squeezing, so last night I had the first ever Tin Shack Invitational Blowdown...

Allan Gott, Randy Kaltenbach and I spent from about 7:30 to midnight blowing beer mugs and other vessles with the first glass from my furnace.

For some reason, beer mugs just seemed so appropriate! :toast:

- Randy

Jay Holden
01-15-2004, 08:50 PM
Richard, Congrats on your success. Looks like you boys had a real fun evening. Good company,good beer and good glass. I can't wait.
Jay.

Richard Huntrods
01-15-2004, 09:13 PM
Originally posted by Jay Holden
Richard, Congrats on your success. Looks like you boys had a real fun evening. Good company,good beer and good glass. I can't wait.
Jay.

Anytime you're in Calgary, Jay!

-Richard

Pete VanderLaan
01-16-2004, 07:37 AM
Do not idle your furnace at 1600 for any short periods. It's OK if you are just parking it for ten days, but it will cause devitrification. 1900F is fine.
:dog:

Randy Kaltenbach
01-16-2004, 08:48 AM
Originally posted by Pete VanderLaan
[B... but it will cause devitrification...[/B]

Pardon my ignorance. devitrification?
- loss of glass
or
- loss of clarity?

Thanks
- Randy

Steve Stadelman
01-16-2004, 09:28 AM
Devitrification is when the glassy matrix starts to come undone. Scummy stuff will start to form on the surface of the glass.

David Williams
01-16-2004, 02:12 PM
Literally, becoming not glass by crystal formation. If glass by definition has an amorphous structure, it can no longer be glass if it acquires a crystalline structure. So it de-vitrifies. Becomes not glass.

Richard Huntrods
01-16-2004, 02:40 PM
Originally posted by David Williams
Literally, becoming not glass by crystal formation. If glass by definition has an amorphous structure, it can no longer be glass if it acquires a crystalline structure. So it de-vitrifies. Becomes not glass.

Cool! (pardon the pun).

I assume, from the previous posts on the topic, that this process is not easily reversed, correct?

Is it "infectious"? That is, once a pot of glass as de-vitrified (and then been emptied), will subsequent charges be more likely to de-vitrify or not?

Related to the last question, would you have to totally empty the crucible (as much as possible) before charging again, or could you charge a pot 1/2 full of de-vitrified glass with batch and make good glass?

Thanks,

-RIchard

Jay Holden
01-16-2004, 05:10 PM
Originally posted by Richard Huntrods


Anytime you're in Calgary, Jay!

-Richard



I've been wanting to attend the Calgary Stampede.
When is that Richard?

Richard Huntrods
01-16-2004, 06:22 PM
Originally posted by Jay Holden




I've been wanting to attend the Calgary Stampede.
When is that Richard?

July 9 - 18, 2004.

For more information have look at:

http://www.calgarystampede.com/stampede/

It is quite a bit of fun. I was born in Calgary, so I had my fill from 1-10 (your parents take you), then from 16-20 (you go with your friends to see who barfs the most on the rides, then again sometime around 20-35 (when your kids are 1-10 and you take them), and finally when you're a grandparent.

However, it's also OK to take visitors. :D

-Richard

Richard Huntrods
01-16-2004, 06:28 PM
Oh yea, almost forgot.

Depending on the year, it will either be wet and cold the whole time, or hot enough to cook eggs on the asphalt streets!

This is Calgary! Our coldest months tend to be November and March - at least by my recollection. Lately, Dec-Feb have been mild (this year extra mild), March has been very cold, and we often get large snow dumps in April and May.

Actually, I now beleive (thanks to the last two years) we've had snow in every single month!

That means the Tin Shack will either be comfortable (if it's rainy), or unbearable (if it's hot)!

Allan told me I should wheel the glory hole outside for summer. That would be cool!

-Richard

Jay Holden
01-16-2004, 07:47 PM
[QUOTE]Originally posted by Richard Huntrods
[B]

July 9 - 18, 2004.

Thanks Richard, I have vacation from July 2nd threw August 2nd. I can't promice but I may be able to make it up there for the stampede this year. That is if I don't go to Alabama to play with the heli pilots at Ft. Rucker.
Jay.

Steve Stadelman
01-16-2004, 09:51 PM
I was in the service, what do you do at Fort Mother Rucker Jay?

Pete VanderLaan
01-16-2004, 10:48 PM
As a fourteen year old boy, I took my grandfather to the fiftieth stampede. He had attended the first one. I loved the chuckwagon races. My grandfather sat on the porch of an old friends house and they argued about protestants and catholics for the entire two weeks. I'm half Irish. The family is in Port Stewart on the north sea. I rode with my grandfather across the giants causeway for four days on horseback. They are wonderful memories. :dog:

Jay Holden
01-17-2004, 07:22 AM
Originally posted by steve stadelman
I was in the service, what do you do at Fort Mother Rucker Jay?

"Grin" Fort Mother Rucker is where I'm Retiring to Steve. I'm an aviation buff and I have friends at Rucker that let me play with the governments toys when I visit. Course now that they are buttoned down from all this terrorisum stuff It may be a little harder to get them to let me play. My pals down there are Heli pilots and they also fly R/C (radio control) Drones. I and my son are R/C pilots and I also fly ultra lites and helicopters. Been doing it for 25yrs. It's my second passion next to blowing glass. When I retire (which may be in 3yrs) I'm moving to enterprise Alabama which is just outside the Fort. Have you been there Steve? If you have I'll say Hi to the Bol Weavle for you.
Jay.

Jay Holden
01-17-2004, 07:24 AM
[QUOTE]Originally posted by Pete VanderLaan
I'm half Irish.

Boy Pete, That explains alot. I'm half Irish Too.:D

Jim Vormelker
01-17-2004, 09:54 AM
Originally posted by Richard Huntrods
Oh yea, almost forgot.

This is Calgary ... and we often get large snow dumps in April and May.

And how is it that I didn't see THAT in the Red Deer Extension Services flyer????


Allan told me I should wheel the glory hole outside for summer. That would be cool!

What fascinating perspective this board gives. If you learn your glass blowing in Southern Calif, you know this is an outdoor activity. Indoor glory holes. What a concept...

Jim V

Richard Huntrods
01-17-2004, 11:21 AM
Originally posted by Jim Vormelker


And how is it that I didn't see THAT in the Red Deer Extension Services flyer????


Beats me! :p Two years ago Randy and I took Darren Peterson's course at Red Deer College's "Summer Series" (2 weeks in May), and it snowed the whole first week.

The glory holes were most welcome! (the entire setup is outside under a very large glass and steel shed - some protection from the elements, but mostly open.


What fascinating perspective this board gives. If you learn your glass blowing in Southern Calif, you know this is an outdoor activity. Indoor glory holes. What a concept...

Jim V

It's the only way when the temperature is -10C!!!

-Richard

Jim Vormelker
01-18-2004, 09:21 AM
Originally posted by Richard Huntrods
It's the only way when the temperature is -10C!!!
-Richard

If you say "-10C" in SoCal, you loose your lease and your driver's license and your car reg, and you have to move directly to Montana, leaving your surf board and outdoor glory hole behind.

Most of the population here came from Keokuk IA or Willowick OH or Cloudersport PA or Cour de Laine ID Kangakee IL. They know where not to get sent back.


You also loose the ability to vote on some pretty stupid propositions in the state-wide elections, whihc many consider to be a benefit ALMOST compensating for the loss of outdoor glass work.

JV