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Dave Bross 11-03-2003 11:42 AM

Virgin homemade clear batch melt
I thought I would try something simple for my first attempt at home batching so I went with the recipe Pete had published a while back:

100 Sand
28 Soda Ash
14 Lime Hydrate
12 Potassium Carbonate
200 grams potassium nitrate
100 grams antimony oxide.

I divided it by ten to get around 15 lbs. of batch and converted it to grams:

4536 Sand
1270 Soda
635 Lime
544 Pot. Carb.
20 Pot. Nit.
10 Antimony

7078 grams total or 15.60 pounds

I tested for moisture in the chemicals by cooking100 grams of each all afternoon and found I had moisture contents of:

1% Sand
5% Soda
2% Lime
1% Pot. Carb.
1% Pot. Nit.

The only thing I adjusted in the formula was the soda. I multiplied the total of soda (1270) by .05 to get 63.5 so I added an extra 63 grams of soda to make up for the water. I know this isn't exactly spot on because I'm making up the difference with wet soda and ignoring the 1 or 2% of water in other stuff, but close enough? I'm thinking I want slightly less expansion if anything because I'll be encasing some things and also have lower expansion colors I can use in case of COE troubles.

I tumbled it in a plastic pail rigged up in a cement mixer for 3 hours and began charging this morning. I'm charging at 2000F and it's going flat and ready for more in about 1 hour intervals. Sweet!

Gentleman, start your hammers!!! it's peer review/whack-a-mole time....

If you see any errors...please do speak up!

I'm thinking my next attempts will be some others Pete gave me involving borax or alumina from nepheline syenite....

Or .....

Am I worrying unnecessarily over glass stability/durability on a glass that will only be used for things like jewelry and C-balls?

Some of the old formulas I've seen for jewelry and knick-nacks have scary amounts of alkalai in them and absolutely no stabilisers, such as alumina or Borax, at all.

Pete VanderLaan 11-03-2003 02:46 PM

The simplist formulas are usually the best. That formula was a derivation I did on Dudleys original formula from back in 68. I think if it is missing anything, it is alumina but it works very well as is and never ever cords up. It takes colorants beautifully and is still used by quite a number of friends I have given it to. Despite the lack of alumina, I wouldn't mess with it since it doesn't seem to like changes in it's cage.

What you did with the soda/moisture calculation is great. My usual problem with moisture is in the potassium
carbonate. It gets very hard and caked on the surface. I will be interested in how it works for you. I recall it having a C.O.E. of about 94.5. :dog:

Franklin Sankar 11-04-2003 11:21 AM

Dave :clap: are you melting at 2000 F . Do you thnk that you will have to go higher? If 2000F works then you have cleared the path for batch using wire furnaces .

Dave Bross 11-04-2003 01:07 PM

This glass is absolutely BEAUTIFUL!!!!!!!It has just a touch less sparkle/refraction than the Glasma but is very, very close to it otherwise. For me, it's nicer to work than Glasma.


It does everything else I want really well too!!!!!

First, to answer Franklins' question, I did all the batching at 2000F. About an hour for the batch to go flat between charges.It took all day because I had to go do other things too. That night I cranked it up to 2200 and cooked it overnight. 8 hours to be exact. I lowered it to 2000F in the morning and it was squeezed out nicely 5 hours later.

It behaves very differently than other batch I've seen. It scared me while I was batching because there were what loked like dark unmelted lumps between the bubbles and I was worried that it wasn't going to melt down without silica stones or some other ugliness. I did use the 325 mesh silica flour.
Shortly after I turned it up to cook I was walking by and noticed a fizzing noise. When I looked in the furnace the glass was just bubbling away like a glass of freshly poured champagne and the dark spots were gone. So nice!

Now here's what else it does really well besides melt...

It is a wonderful torch working glass.

It has a lot of thermal shock resistance.

It has a combination of softness and working time that I really enjoy.

The powder is really a mess so I have to work on some things to make adding the batch a little neater. That's the only drawback so far and I can definitely live with that.

My quick version "shade tree" expansion testing, which consists of pulling threads of different glasses to compare against would seem to put it somewhere around 94-5. A little higher than FHC, very close to Gaffer, and a little lower than Spectrum.

I think a dilatometer will be a "near future" project.

I figured the oxide percentages on it and was quite surprised....

74% sand
12% soda
8% lime
6% potassium

That's a lot of sand. I'm thiking this should actually be quite durable because of that?

Question for Pete...

For historical interest if nothing else, why did you go from this recipe I just melted to:

63.25 silica
20.25 soda ash
9.06 Hydrated lime type N
2.18 Borax 5 mole
5.25 Potassium carb
100 grams antimony oxide
130 grams potassium nitrate.


50 sand
20 1/4 soda ash
9 1/16 hydrated lime type N
5 1/4 Potassium carb
3 3/16th Borax 5 mole.

as a color base and clear? I haven't figured the percentages yet but it looks like the only major change is the borax?

Pete VanderLaan 11-04-2003 01:42 PM

The first formula does have a ton of silica and it is durable and the silica content is why the glass works well in a torch. It was a glass I used that I cut and polished a lot and it polishes beautifully. That is because of the potash.

The second formula is a glass designed to fit SP87 hand in glove. I use it for my red and opal silver amber formulations when matching SP87. It also makes a very nice turquoise blue I am currently working. SP87 color base makes OK reds but the ambers are dirty from all the spars that Tom has in there, so this stuff is spar free, which is key to color glasses.

The third formula is simply wrong.

Interestingly in our drought, I have increased the amount of Soda ash in that glass from 20.25 to 20.75 to keep it in line with the Spruce Pine.

I would melt hotter than 2000F unless you rigourously follow the Corning Protocol of turning it up after the melt reaction is complete. Using 325 mesh sand is a two edged sword. It melts easier but it also clumps easier. It can get very problematic when the humidity goes up and in a cold melt, it can create silica stones. At the same time I say that, if the dusting bothers you, you can spray the batch with a nozzle from your local greenhouse that gives a fine mist. It will knock down the dusting. Mist to taste. It's kind of messy. :dog:

Franklin Sankar 11-04-2003 05:26 PM

Seems that the lower Temp. works well for Dave so why would you want to go higher? Is it faster or some other special benefit?
If you use larger size silica sand what happens? Would it still work?

Dave Bross 11-04-2003 05:36 PM

Many thanks Pete! It never would have been possible to get something so incredibly nice on the first try without a whole lot of help.

More questions of course....

On the batch I just melted...

If I wanted to take the COE down to the 92-3 range to fit Fenton stuff, up to 96 to fit Spectrum, or even go completely nuts, kiss durability goodbye, and try taking it up around 102-4 to match Moretti, how would I go about it?

Would adding certain amounts of silica or soda be enough, or do the other things need to change on a percentage basis along with that?

What is the Corning Protocol?

I did melt it at 2200 after I got all the batch loaded and I'm pretty sure I would have screwed it up if I had tried at 2000.

Pete VanderLaan 11-04-2003 06:30 PM

drop or raise the quantity of soda by one pound to move the C.O.E. about one full point - based on a 100 lb batch.
You will have to play with it but it's ballpark.

The corning protocol is simply that you want to melt as cold as you can get away with and then to turn it up after the mass has melted. The notion is that the lower the temperature, the less attack on the refractories which yields less pot wear and less cords ( up to a point). It's relative to the cording potential and general meltability of the glass. Sometimes melting cold means 2200 F and that's where I melt SP87. I have fluorine glasses I melt at 1900F. You have to be willing to experiment, and to have a few genuine disasters.

As to franklin's question. the lumps Dave saw were perilously close to staying lumps, and they were unmelted silica. I would not melt it that cold or if I did, the quantities would be tiny. The tendency in a large batch pile, say fifty or sixty pounds is for the outside to melt first and for the core to gradually heat up and fuse. You don't want that fusion to go on too slowly or you will get agglomerated big honking piles of snot- ( a highly technical phenomena well worth avoiding..)

Jay Holden 11-04-2003 08:32 PM

Man I'm soaking this post up like a sponge. This is great! Thank's you guys.

Franklin Sankar 11-05-2003 08:06 AM

I know what you mean Jay. Thanks to Pete and Dave for sharing.

Dave your sand must be low iron or did the chemicals decolorize?
If I have to import the sand I would loose the benefit of reduced shipping cost. In fact when you add the cost of all the chemicals it may be more than SP but then you have to add shipping sand cast. It depends on what you want from the batch, but I remember Pete has been saying the best deal is still with SP. Dave how does it compare with SP?

Pete VanderLaan 11-05-2003 08:36 AM

The whole low iron sand is a red herring. It's the feldspars that turn glass coke bottle green, unless the sand is really awful. Any pottery supply silica is good stuff. :dog:

Dave Bross 11-05-2003 10:33 AM

Thanks again Pete.

Pottery supply silica is exactly what I'm using here and the glass is gorgeous. As for freight for Franklin (Freight for Franklin, sounds like a great name for a kids book, no?)I guess Florida is about as close to Trinidad as we're going to get in the continental USA.

22 cents a pound for the silica 325 mesh, Axner pottery supply, at ...

I'm sure they're used to shipping to the Caribbean. They are extremely nice at Axner and may be able to get you other things you need if you ask.

All the other chemicals were right around 20-5 cents a pound in bulk, with the exception of the potassium chemicals, which were 73-5 cents a pound. Those came from Brenntag, a major chemical supplier.

I'm using an incredibly nasty fireclay crucible for the experimental melts. This thing has so much iron in the clay that there are BIG rust spots inside. The glass off the top shows perfectly clear on the cross section of a cut cane, and that is very rare not to see green or grey (from decolorizers) on the end of a cane. Glasma is the only other glass I've ever seen this clean. Once you get down in the pot a bit the green begins. Still not too bad, considering the crucible is as nasty as it is.

Another BIG plus for this glass is minimal toxic stuff. The tiny amount of antimony is the only nasty thing in it.

I'm really liking the concept of being able to batch it up and adjust the COE right here at the house. No calls to make, no freight to pay and no waiting and wondering.

The more I play with it the more I like the way it works, and the way it melted was even easier than cullet in my opinion. I've never had a glass squeeze so easily, and I'm using a tall, narrow pot so the bubs have way further to go to get to the top.

Pete VanderLaan 11-05-2003 11:47 AM

It is true that it is a sweet squeezing glass. I think the great advantage to making it yourself is that if you make an unoxidized form of this stuff- leave out the nitrates, that while harder to fine out, if you always off-load from the mix what you want for color and then add nitrates for the clear part so you can't ever have incompatibility even if you make a mistake at the scales.

Back with your adjusting of the formula, and your decision to only mess with the soda just needs a brief observation. If the moisture content of the silica is 1 percent, that means that you are off one pound silica per 100 lbs loaded, which is not insubstantial. Usually when I am fine tuning a formula, I always do it with the silica and usually it is less than 100 grams per 100 pounds batch to move the formula to where I want it, unless I have seriously screwed up. In general, I don't like to mess with the potassium/sodium ratios at all when adjusting. The silica is very powerful as an adjusting chemical and it can be moved with very little recourse. This is never mentioned in any books on the subject and Soda is always referred to as the holy grail for adjustments. I advise you to not use the soda for that purpose or at least be cautious with that.
63 grams of soda in 15 lbs of glass is quite a bit and is probably driving the expansion up about one full point. That may be a good target amount when you want to push this stuff around. Either that or adjust the silica about the same amount..

It is by the way really heartening to me to see some of you playing in this particular sandbox. There are so few of us now and it really makes me feel that my efforts here at craftweb are worth it just from the pure educational aspects. :dog:

Brian Gingras 11-05-2003 12:18 PM


Originally posted by Pete VanderLaan

It is by the way really heartening to me to see some of you playing in this particular sandbox. There are so few of us now and it really makes me feel that my efforts here at craftweb are worth it just from the pure educational aspects. :dog:

your efforts do not go un-noticed...I'm 2 years from lighting up my own shop, and this discussion still has had my full attention. Once I get my equipment where I want it, I plan to do the exact same thing, that is to make a glass that I like and fits my needs...having been renting time in other shops and having the base glass changed all the time, I've been fixed on doing the glass batching myself so I don'r have to deal with the changing supplies and unreliable sources.

This kind of discussion is something that all members of the glass comunity need to pay attention to.

Franklin Sankar 11-05-2003 01:01 PM

This really is the best news, especially about where the iron comes from. Thanks Pete.

Jeff Wright 11-05-2003 04:18 PM

Best thread in a long time...

It is by the way really heartening to me to see some of you playing in this particular sandbox. There are so few of us now and it really makes me feel that my efforts here at craftweb are worth it just from the pure educational aspects.
Even though I still am a studio renter and at the whims of the studio owners, I am following this thread with a lot of interest. I'm certainly taking notes. I'm with Brian and probably at least a year and maybe two from my own shop. However I still want to learn as much as I can before firing up.

Pete, thanks for all you have done here at CraftWeb.

All, lets keep these discussions freely flowing!

:) :) :)

Bob Boyd 11-05-2003 04:34 PM

This has been a great thread for even the newest of newbies. Makes me wanna go batch some glass. I particulary liked the discussion about cost and COE adjustments.

Pete you said this would make an excellent color base. Can I ask what chemicals/materials and quantities would be added to yield different colors?

Bob Boyd

Pete VanderLaan 11-05-2003 04:53 PM


Originally posted by Franklin Sankar
This really is the best news, especially about where the iron comes from. Thanks Pete.

Well, don't get carried away, get the cleanest sand you can. And Dave, keep in mind that Nepheline Sy is really a spar.

As to the technical education, it's why I'm interested in the conference, it certainly isn't happening in the schools anymore.

Jay Holden 11-05-2003 06:11 PM

Pete and Dave, Thanks for the insightful post on batching. I'm following with great intrest and with pen in hand. I have an empty shed just waiting for the raw materials. So you say to use pottery silica? Everyone at work are telling me I can buy good batch from Lewis in Corning cheaper than I can batch my own. I know that GlassArt in Watkins Glen uses it in their Electroglas furnace with good results but I think I'd still like to try making it myself.

Pete VanderLaan 11-05-2003 07:36 PM

If you want really nice glass it is probably going to contain either potash which gives lustre or barium for brightness and neither is cheap. It is not going to contain spars which are very cheap.
As to price, it probably will be cheaper from Lewis. Dave quotes 72 cents lb for potash and I pay 50. I buy a lot more. Silica should really be about 13 cents in bags and is dirt cheap in 1 ton cloth baggies. I think the difference is that you know where everything came from- you made it- and that is power.

I use SP87 for a clear when I am working it with colored glasses. I would not use it as a stand alone clear and would make either the formula Dave has listed that I wrote almost thirty years back, or a very nice 11% lead glass I pull out for special occasions. The glass should be appropriate to the project.

Just remember, get a good scale, a very good scale. I have two and I cross check every time. :dog:

Mitcheal Veenstra 11-05-2003 07:46 PM

This is great stuff folks... It's makeing thing about trying the batch thing in my little Mark L 15 pound furnace...

Pete, would this qualify for the Classics forum? It is certainly a boon to us low timers here.

Dave Bross 11-05-2003 07:48 PM


Not to worry about the nepheline syenite...

After seeing this glass I believe that I too will invoke the "no spars" rule in my glass making. Much like my "no guts" rule for eating meat. You only go around once so you might as well try for the best you can get. I will melt some other glasses just for the knowledge but I am just blown away by this particular one.

I hear you on the silica adjustment. That's straightforward if I'm going down in expansion, once I figure out exactly how much it takes to move it.

I'll adjust for the 1% moisture in the sand on the next one. I think you're right about bumping it one point with the 63 grams of soda. In my rough guestimates of expansion via thread pulls it comes closer to some older gaffer clear canes that I have than anything else, and I think those are supposedly around 95.3 COE. I suppose I may be retaining a bit more soda/potash in the melt due to the lower melt temp. too. I definitely haven't quite hit 96 COE yet though.

I'm thinking I might be good at my current COE, close enough to 96 to put 96 color on the outside of the clear, and I'll have a bit of compression in the clear from the slightly lower COE if I use it to encase 96 color.

If I want to go up in COE would it be wiser to maintain the ratio between the potash and soda but increase quantities of soda/potash, or just back off on the sand?

Any suggestions on annealing temps?

And....particular thanks for pointing out the idea of mixing the color base as stock and adding the nitrates and antimony when needed.


I'm sure you've noticed all the turmoil, sudden surprises and trouble surrounding batch and cullet supply lately, or should I say always? How about batch or cullet that is not quite on spec. like the chinese stuff? At least if I screw up on the scale or something it's a quick fix. Speaking of screwing up...I'm writing each measurement down as soon as I finish it. I know just how easily I could forget or be distracted.
I find it very exciting to have this level of freedom in having control and adjustability on what I'm using. Particularly having a "one fits all" for becoming oxidising or reducing batch on one mix.

Bob Boyd,

For me, the best general and most easily digested info when I was beginning to think about color, and actual percentage suggestions, was a copy of the book "Modern Glass Practice" by Scholes. It's out of print and hard to find but not impossible. Try Whitehouse books in Corning NY or

Pete VanderLaan 11-05-2003 08:01 PM


Originally posted by Bob Boyd
This has been a great thread for even the newest of newbies. Makes me wanna go batch some glass. I particulary liked the discussion about cost and COE adjustments.

Pete you said this would make an excellent color base. Can I ask what chemicals/materials and quantities would be added to yield different colors?

Bob Boyd

That is a loaded question. I am writing a book on it and teach a class in it once a year. I think that if you refer to "Glassnotes" you will find rudimentary coloring stuff. There are also tons of things in these archives that I have written from time to time and you should start there. Dave is also right that Scholes has some good basics as does "A textbook of Glass Technology" by Hodkin and Cousen from back around 1915. I may give a very short course at the conference, and I may not since I anticipate being a little harried.

And this is not meant to put you off, I just don't like glossing over stuff so I don't want to write a treatise right now. I will however sell you one when I finish it.

As to Daves questions, move the sand, you have tons to work with. Moving the alkaline stuff frequently causes cords and that is one very cord free batch. And yes it has occurred to me that this thread will move to classics. It's nice to be back on the subject of glass.

Is Scholes really out of print again? :dog:

Dave Bross 11-05-2003 08:30 PM

That may or may not be correct on Scholes being out of print. I couldn't find it new when I lucked into my used copy, but that's not to say it isn't out there new.

I love my used copy, it's from 1951 and has lots of fun trivia things like glassmakers not having access to Uranium at that time for fear of the commies getting their hands on some.

Pete VanderLaan 11-05-2003 09:52 PM

I too have a first edition and it is chock full of that sort of stuff. My copy of Tooley, which is an absolutely worthless book called "Handbook of glass manufacture" reveals such secrets as "Remmy " Brick which was a 95% Alumina brick AP Green made in the sixties and seventies was named after the AP Green president George Remmy from the 1950's. I assume that most people know that "Mizzou" is slang for Missouri, or the university. I see it mispelled all the time. Kast-o-lite is probably a lighthouse on the Mississippi or a cave in the Ozarks. I am off to Oxaca for a week to see my daughter who is in school there, so don't start any political conversations that get Bob all worked up.

One last thought. When you mix a batch, always always always stick a 3x5 card in the actual batch can or bag saying what it is. It's amazing how fast you can get them mixed up, like 45 minutes.

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