Beebop Posted June 27, 2021 Report Share Posted June 27, 2021 Hi all! six months ago i bought my first batch of materials for making test batches of glazes. this included 1 lb of talc. the local supplier only lists 1 type of talc on their website, Texas Pioneer, however the talc i got in December was white and the hand written label said CT-30 cal talc. is this Montana talc? Calcined? i can’t find this name in Glazy and Digitalfire only has a place holder for it, not much more. My receipt listed it as Texas Pioneer, so I didn’t think much of it and thought that the standard talc must be white calcined Texas talc. Fast forward 6 months and i’m out of talc. i just bought 5lbs from the same supplier, opened the bag and it’s dark grey! I gasped! This I’m assuming is the Texas Pioneer. But how does it compare chemically to the other talc i’ve been using for 6 months? Is this grey talc only used for ceramics bodies or is this a normal ingredient for glazes? The talc materials listings in Glazy are all white powders not grey. i will also mention that i am a big fan of magnesium in glazes. i’m spending a lot of time trying to make ^6 kakis and magnesium mattes so i want to make sure i’m using materials that are reliable and consistent! are they considerably different, and if so, which would you recommend and why? i feel like this just added another six months of testing to get to where i thought i was already! I will call the supplier and ask tomorrow, but Ive found them to be hit or miss when asking for precise info, so hoping y’all can help me out! Link to comment Share on other sites More sharing options...
PeterH Posted June 27, 2021 Report Share Posted June 27, 2021 This excerpt from Digitalfire may partially explain the colour difference. Note the [extra?] LOI.https://digitalfire.com/material/talc Link to comment Share on other sites More sharing options...
Beebop Posted June 27, 2021 Author Report Share Posted June 27, 2021 when i switch in Glzy from “talc” to Amtalc C-98 (which I’m thinking now is Pioneer Texas talc, yes??), the UMF count for Mg and Si go down, the COE goes up, and the LOI goes up, so it sounds like gram per gram, Texas Pioneer has less of the good stuff and more of organics that burn off in the firing. I guess I still don’t know how CT-30 compares to generic talc listed in Glazy, and how this change actually impacts my recipes. Sounds like I have some recalculating to do if i’m switching Mg sources! Link to comment Share on other sites More sharing options...
Min Posted June 27, 2021 Report Share Posted June 27, 2021 It's my understanding that CT-30 talc also went by the name Desertalc. Amtalc C-98 is the newer name for Pioneer talc. Use as accurate an analysis as you can find for your chemistry, not a theoretical one. Comparison of Desertalc to Amtalc C-98 (Pioneer talc) below. I would adjust the calcium, magnesium and silica for sure. While you're at it you could tweak the sodium and potassium to match also. Link to comment Share on other sites More sharing options...
Dick White Posted June 27, 2021 Report Share Posted June 27, 2021 Also be aware that the Texas Amtalc C98 (which at one time was branded as Pioneer, same stuff different name) is going off the market at variable rates depending on the depth of the inventory at the distributor that services your local supplier. The Amtalc mine was bought by DalTile a few years ago, and a few months ago they decided to stop selling it outside of their own production needs. As soon as you figure out how that 5 lbs works, you'll have to deal with talc from a different source. The joy of potting. Link to comment Share on other sites More sharing options...
Beebop Posted June 28, 2021 Author Report Share Posted June 28, 2021 Thank you all this is incredibly helpful! looks like either way i have some adjustments to do to my recipes, as i haven’t been mixing to chemistry i thought i was! i see an incentive to stick with CT-30 / desertalc if Pioneer is on its way out, but what a bummer, since after the LOI is burnt, its a purer form of magnesium silicate! i’ll see if the supplier will let me exchange, if not i’ll enjoy it while i can. thanks all! Link to comment Share on other sites More sharing options...
Min Posted June 28, 2021 Report Share Posted June 28, 2021 8 minutes ago, Beebop said: see an incentive to stick with CT-30 / desertalc Wouldn’t recommend this, it’s unusual you actually found a suppler with this. It hasn’t been readily available for years. Since you are using glaze calc rebalance the formula with what’s available to you. Buy enough to last a few years. Link to comment Share on other sites More sharing options...
Beebop Posted June 28, 2021 Author Report Share Posted June 28, 2021 oh i had no idea, but that makes sense why it isn’t listed in Glazy. This is all so helpful, I assumed I had calcined Texas talc for the last 6 months! Now i suddenly have the urge to hoard what i was about to exchange ha! Link to comment Share on other sites More sharing options...
Mark C. Posted June 28, 2021 Report Share Posted June 28, 2021 CT-30 / desertalc was long gone over 20-30 years ago, so your supplier had a bit of new old stock. I still use a bit to this day but its almost gone,one bag left..Do not bother thinking you will find more. In terms of Texas talc which has been the main talc most use for decades it going away very soon if not already. Its grey in color. You may be abloe to still buy some bags I have used sierra light (a white talc for many decades) Its a white talc and costs more$ My suggestion is buy a supply (lifetime preferably) and adjust your glazes for it and not worry about supply side issues. I have a few glazes that use different talc types Suppliers like laguna Clay Co. are scrambling to replace Texas talc at this time welcome to the forum and good luck with the talc hunt. Link to comment Share on other sites More sharing options...
Bill Kielb Posted June 28, 2021 Report Share Posted June 28, 2021 3 hours ago, Beebop said: oh i had no idea, but that makes sense why it isn’t listed in Glazy. This is all so helpful, I assumed I had calcined Texas talc for the last 6 months! Now i suddenly have the urge to hoard what i was about to exchange ha! You might not want to fret too much as talc is likely going to be a small percentage of your recipe so when rebalancing you may not even have the precision or may notice a negligible change in the overall recipe. So even though there is a 75% increase in CAO between the talcs above and let’s say talc is a whopping 10% of the recipe then we are talking 7.5% of a very small number. The point is, entering it into the calc software may reveal only very minor changes to the recipe or none at all. Pretty easy to see using the software. Link to comment Share on other sites More sharing options...
neilestrick Posted June 28, 2021 Report Share Posted June 28, 2021 I don't use much talc at all, even with 15 different glazes being used in my studio. Most recipes that have magnesium also have calcium, and dolomite can take care of most or all of the magnesium. Link to comment Share on other sites More sharing options...
Beebop Posted June 28, 2021 Author Report Share Posted June 28, 2021 i haven’t been using dolomite, just whiting and talc, but i can see the benefit of adding it to my list, and augmenting the ratio with talc or whiting when needed. thanks! Link to comment Share on other sites More sharing options...
oldlady Posted June 28, 2021 Report Share Posted June 28, 2021 beebop, getting the largest bag that is sold is a good practice for any chemical you use frequently as well as this talc. if you have room to store your glaze materials, get them now. nearly all of my big Rubbermaid 18 gallon tubs were filled more than 20 years ago. granted, i am not a high production potter but i have not had to face so much of the change that others have over the years. some of the tubs are less than half full these days, hope they are the ones that have not changed. Link to comment Share on other sites More sharing options...
Callie Beller Diesel Posted June 28, 2021 Report Share Posted June 28, 2021 Also, it’s good to note that Digitalfire has a larger database of specific materials and their analyses. It’s an older website, so they’ve had more time to document the shifts in various popular materials. Lots of old recipes out there that call for materials that aren’t available anymore and need reformulating. Or you come into a stash of materials from someone who has retired, or is selling an estate. Link to comment Share on other sites More sharing options...
Beebop Posted June 28, 2021 Author Report Share Posted June 28, 2021 2 hours ago, oldlady said: beebop, getting the largest bag that is sold is a good practice for any chemical you use frequently as well as this talc. if you have room to store your glaze materials, get them now. nearly all of my big Rubbermaid 18 gallon tubs were filled more than 20 years ago. granted, i am not a high production potter but i have not had to face so much of the change that others have over the years. some of the tubs are less than half full these days, hope they are the ones that have not changed. agreed! i went small for my first purchase since i’m just starting to figure out what i want to work with, and ramping up from there once i have a better idea. building a home studio has been such an interesting investment, i certainly haven’t been able to go big on everything from the start, but i’m learning how to pick and choose my battles. i definitely see bulk bins in my near future though. thanks! Link to comment Share on other sites More sharing options...
Dick White Posted June 29, 2021 Report Share Posted June 29, 2021 @BeebopFor this gray Amtalc C-98 talc, definitely go big now while you can still get it. You might not be able to get it in another month or so. Then you will have enough to settle in on. The other materials will likely continue to be reasonably available, so a smaller quantity will not leave you in the lurch. Link to comment Share on other sites More sharing options...
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