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Help On Ingredient Substitution Needed!


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The clear glaze cone 6 I am making right now calls for:

 

soda feltspar 70

bentonite 3

lithium carb 3

dolomite 7

zinc oxide 5

quartz (or flint) 12

 

unfortunately, just realised I don't have any lithium carbonate, can I substitute it with Barium Carbonate which I do have, or a bit more of one of the other ingredients and still get transparent glaze???

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The only other source for Lithium that I know is Lepidolite, a lithium Feldspar.It is not on the market very often. I still have some.

I think it would be easier to get a little Lithium Carb.

It works well as a wash flux with oxides, so you could use it elsewhere.

 

Marcia

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Ask your local independent pharmacist for expired Lithium pills. They are 250mg/pill. Why they expire has always been a mystery to me.

 

If you explain how you are going to use them in glazes, he may give you some. Otherwise, he has to pay someone dispose of them...

 

Good luck,

Jed

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Dropping the 3% lithium carbonate raises the COE from 7.65 to 7.66, an insignificant change.

 

My best guess is leaving out the Lithium Carbonate should produce virtually the same identical glaze.

 

Adding barium carbonate would provide no advantage I'm aware of and could possibly cloud the clear glaze.

 

Without the lithium, this clear glaze might react somewhat differently with colorants, but probably not.  Frankly I don't understand why 3% lithium carbonate was added to this recipe.

 

The addition of the 5% zinc oxide is making this clear glaze into something of a zinc semi-matte.  "Mastering Cone 6 Glazes" uses 10% zinc oxide in their Zinc Semi-Matte.

 

 

Just for reference you can also use spodumene or lithium fluoride as a replacement for lithium carbonate, in addition to substitutes already mentioned by others.  Spodumene will be a little less fluxy and lithium fluoride a little more fluxy. But I can't imagine why it was added at all.

The clear glaze cone 6 I am making right now calls for:

 

soda feltspar 70

bentonite 3

lithium carb 3

dolomite 7

zinc oxide 5

quartz (or flint) 12

 

unfortunately, just realised I don't have any lithium carbonate, can I substitute it with Barium Carbonate which I do have, or a bit more of one of the other ingredients and still get transparent glaze???

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For a glossy clear ^6 I use:-

 

20 Potash Feldspar

20 Standard Borax Frit

15 Wollastonite

20 China Clay

6  Talc

19 Silica

 

for a creamy white add 4 Tin oxide

 

If you have those ingredients, this works well for me on  Earthstone ES5 and the  Standard Buff stoneware at college. .

 

There must surely be even simpler recipes for a clear glaze.

 

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Guest JBaymore

You can't simply sub somethiong like spodumene for lithium carbonate.

 

The issues here are understanding that the raw mateial is not what is present on the pot when you open the kiln, the concept of the relative molecular weights of compounds, and the fact that the chemical compounds in different raw materials can provide different compounds in the final melt.

 

Lithium carbonate has the chemical formula LiCO3.  In the kiln it converts to Li2O ...... which  is what is the flux on silica.... (the carbonate is NOT a flux....it supplies the flux ... important distinction).  When you weigh out X grams of lithium carbonate you are weighing out a certain amount of lithim atoms.....but ALSO one carbon and three oxygens per lithium atom.  The carbon and some oxygen are given off in the kiln as CO2 gas. 

 

If you subsitute spodumene directly for the weight of lithium carbonate in the recipe, the amount of Li atoms in that same X grams in the recipe is going to be WAY different that what you had in the original.  And in fact you are also going to ALSO be adding other ceramic active components like alumina and silica.  The approximate formula for spodumene is  1 Li2O - 1 Al2O3 - 4.1 SiO2. 

 

One molecule of lithium carb gives you one half of a molecule of lithium oxide in the final melt. One molecule of spodumene gives you one molecule of lithium oxide in the melt..... but also one molecule of alumina and 4 molecules of silica.

 

The molecular weight of spodumene is 380.4.  The molecular weight of lithium carbonate is 29.8.  Relative weights are 380.4/29.8 .  Spodumene is almost 13 times heavier than lithium carbonate.  If you weigh out the same amount of spodumene as was called for as lithium carbonate..... you are going to get about 1/13th the atoms of lithium as the original recipe,.... plus some alumina and silica that were not there in the first place.

 

This is why one learns glaze calculation.....or at least how to use glaze calc software.

 

best,

 

...................john

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