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Need help identifying glaze materials

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Hello again.  During the course of carting around all these glaze materials for 30 years, the labels on the cans faded or fell off, except ironically for Colemanite and Magnesium Carbonate. I have contacted quite a number of different resources about identifying the remaining materials to no avail. I know that any acid will  cause whiting to fizz....but am at a loss as to how to identify the others. These are common materials like dolomite, whiting, silica, talc etc.  I have put in an order for new materials....I just had Depression Era parents and it just bugs the hell out of me to waste these materials. Any hints on how to identify them would be most appreciated! 

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I don't know an inexpensive way to do it... You can buy reagents and probably deduce what you have by reaction, or you can send samples out to a laboratory, but both of these can get pricy.  Clays will act like clays when mixed with water, zinc (especially old zinc) will clump together into hard chunks but still be quite zinc-y if you know what I mean.  I think dolomite, whiting and talc will all react with acid, so might be difficult to tell the difference.  My talc is always grey but i think it comes in white as well, it is quite slippery in the hands though (the other two aren't).  

I don't recommend a taste test because you don't know what it's been exposed to. 

I'm curious what the others here will say, sounds like a fun adventure

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If you know somebody with a supply of glaze materials, maybe you can take some samples to them for comparison. Many materials have unique appearances, despite all being white powders. The other option is to test fire a small glob of each and compare the results to fired samples of known materials.

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On 5/31/2019 at 7:55 PM, Mark C. said:

I think all the spots are from the clay body. Not the glaze.

The glaze looks like any oatmeal glaze of that time on an iron bearing claybody

My honey white is similar . I foire to cone 10 reduction

The huge range of glaze melt from cone 6- to cone 10 is a larger issue . I have no info on that glaze. My honey white does not look good at cone 6 

I use kingman every week but I bought 3,000#s in 1982 from the mine-I'm on my last 400#s now-hopefully it will last until I'm done.\

You should be able to make that glaze with custar feldspar or any potash spar

How about talking to any of your 35 year old potter friends from that era for that reciepe??

You can toggle thru glazy on the web for a look alike. Remember its on a iron bearing clay body .

I have  glaze like that buts its cone 10  only not cone 6.

 

 

19 hours ago, JohnnyK said:

How much volume of individual chemicals are you talking about and is it worth the time, effort and expense to analyze what you have?

As much as 30 pounds....so not an insignificant amount. At least I could identify bentonite. 

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Thanks to Mark C for volunteering to try to identify these materials.  Two did react to vinegar....but if all else fails...I will resort to molecular weights for a clue. 

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On 6/11/2019 at 11:48 AM, liambesaw said:

I don't know an inexpensive way to do it... You can buy reagents and probably deduce what you have by reaction, or you can send samples out to a laboratory, but both of these can get pricy.  Clays will act like clays when mixed with water, zinc (especially old zinc) will clump together into hard chunks but still be quite zinc-y if you know what I mean.  I think dolomite, whiting and talc will all react with acid, so might be difficult to tell the difference.  My talc is always grey but i think it comes in white as well, it is quite slippery in the hands though (the other two aren't).  

I don't recommend a taste test because you don't know what it's been exposed to. 

I'm curious what the others here will say, sounds like a fun adventure

I am thinking if all else fails...molecular weights. 

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On 6/13/2019 at 6:00 PM, liambesaw said:

Lol good luck, IMO there's no way to do that with mined minerals, too many impurities and variation to get even close

Oh...I think it's possible simply through a process of elimination....eg silica is 396. something g per mol whereas talc is something like 183.. which means that if you compute ratios between the substance, you should be able to get close. ..(just off the top of my head here)...then there is always specific gravity.  But I sent them off to Mark.  Two of them fizzed with vinegar meaning one is Whiting and the other is talc. I see that we are neighbors....I am in Coeur d'Alene.  I am mostly interested in this now because Mark needs my 30 year old talc for one of his recipes.

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39 minutes ago, neilestrick said:

Does dolomite fizz, too?

Yes it does. 

Talc would one of the easiest to identify just by rubbing it between your fingers, if it feels soapy or waxy it will in all likelihood be talc.

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Wollastonite, dolomite, several Frits, bone ash among others are significant sources of Calcium which will likely react. It looks like this will be an interesting difficult project with intelligent guesses as an essential part of determination.  Calcium containing materials listed highest to lowest below.

for Talc I am thinking the feel test and a reagent for magnesium would be easiest.

F9222FB1-663B-4E15-93DB-30060027DB5D.png

Edited by Bill Kielb

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As well as non fritted forms of calcium containing materials (in carbonate or oxide form) all the carbonate forms of metals will react with an acid  creating carbon dioxide bubbles (fizz) also. Strontium carb, barium carb, lithium carb etc. will all fizz with an acid.

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Only two reacted to vinegar....both about equally. The other three did not.  We are not talking complicated chemicals here. The ones identified already were  Colemanite, Bone Ash,  EPK, Kingman, magnesium carbonate, Barium carbonate,   and G-200.   The remaining ones are most likely Whiting (calcium carbonate), Talc, Silica, Dolomite,  and ? (possibly more bone ash).  In the days I was potting we did not use Strontium, Lithium Carb, frits, Neph Syenite.  or any of these other exotic chemicals you use now. Things were pretty darn basic.  There was no "Laguna"...everything was Westwood or Duncan...that was it.  I know it's kind of hard to get your heads wrapped around that...but things were pretty darn basic. We didn't have 500 clays and glazes to chose from and materials were quite limited.

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So talc -  feel, look and magnesium reagent only,  dolomite -  strong calcium and strong magnesium reagent (both react), whiting only calcium reagent, Bone ash - likely calcium reagent and volume mass. Sounds like you have it mostly figured.

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Whiting has that fishy sea smell to me. Guess that's because it's made from sea shells. Dolomite and talc look similar to me. Silica, not sure, firing a sample of each will give some good data to guess from. Maybe do a sample  by itself and a 50/50 mix with silica. 

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I think for Silica you could look at under a microscope(cheap one) and see the quartz particles relatively uniform in size to give you some confidence. Maybe even cell phone magnifier, need to try later today.

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interestingly enough....the weight by volume, although not resulting in the exact weights, did result in the exact ratios. Out of the five materials, #4 was identified by Mark as being Zircopax.  Numbers 3 and 5 turned out to be almost exactly the same weight....with 3 reacting to vinegar and 5 not and being being slightly hydrophobic reminding me that talc often floats on water. So...I would bet 3 is calcium carbonate and 5 is the talc....which would be great for Mark because there is about 30 pounds of it.   Numbers 1 and 2 were also in the ratios of dolomite and silica with 1 having reacted vigorously to vinegar. So...we'll see what tests say. 

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This is an excellent article. Thank you!  I have a bisque coming up and am going to try the volume loss in that bisque.  Dolomite and Whiting are very close. So I am wondering if I can get enough material out of the bisqued pot to distinguish between them but I will try!  At least I will know if the other one is silica or feldspar. 

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If you've got it down to Dolomite vs Whiting ... What temperature do you normally fire to? 
If it's cone 6 you might try this from https://digitalfire.com/4sight/material/calcium_carbonate_173.html

The difference between dolomite and calcium carbonate in a glaze

The difference between dolomite and calcium carbonate in a glaze

These glaze cones are fired at cone 6 and have the same recipe: 20 Frit 3134, 21 EP Kaolin, 27 calcium carbonate, 32 silica. The difference: The one on the left uses dolomite instead of calcium carbonate. Notice how the MgO from the dolomite completely mattes the surface whereas the CaO from the calcium carbonate produces a brilliant gloss.

 

 

 

 

Advice offered from a position of complete ignorance, use at your own risk.

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