Advice On Batch In A Wire Melter

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]

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....&threadid=2065

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

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]

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.

[Ben Rosenfield]

No sweat. It'd be my pleasure.

And thanks in advance, David.

[Richard Huntrods]

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]

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]

Steve,

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

-Richard

[Randy Kaltenbach]

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?

[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.

[Steve Stadelman]

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]

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]

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]

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!

[Pete VanderLaan]

you're absolutely sure it's not because you have latent masochistic tendencies?

[Richard Huntrods]

Geez - you molly minders just won't quit, will you? I get less flack from the gas melters.

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, This is a "wire furnace" thread. We don't got no molly religion here!

Cheers,

-R

[Pete VanderLaan]

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.

- 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]

Originally posted by Richard Huntrods
Geez - you molly minders just won't quit, will you? I get less flack from the gas melters.

.

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

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.

I thought we just did this gig. if its wire use cullet hands down.

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]

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]

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]

Would using quartz-encased elements help guard against damage caused by batch? Or would this introduce other issues -- aside from increased cost?

[Dave Bross]

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