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#1
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Talc!
The writing on the wall is that the University is not going to allow us to
use Talc either in our glazes or our clays (how in the world you are supposed to find that out given the mix we have that has come and gone and the recycling done...). Our best glazes use Talc. What in the world can you do to substitute it especially given that I have used it to keep glazes from crazing and it is the only thing that worked. Donna |
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#2
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Talc!
"DKat" wrote in message ... The writing on the wall is that the University is not going to allow us to use Talc either in our glazes or our clays (how in the world you are supposed to find that out given the mix we have that has come and gone and the recycling done...). Our best glazes use Talc. What in the world can you do to substitute it especially given that I have used it to keep glazes from crazing and it is the only thing that worked. Donna Talc adds magnesium to glazes and is used as a flux in some low fire clay bodies to lower the maturing temperature and extend the firing range. It is primarily used in white hobby and school type modeling clays. I'm not sure what would substitute for it in a clay body, perhaps a frit or other prepared fluxing agent. Or, perhaps dolomite and silica could serve this purpose in a body. Talc is magnesium silicate and provides both magnesium oxide and silica to a glaze. Magnesium can be gotten fom dolomite which is a calcium, magnesium carbonate or from chemical magnesium carbonate. If substituting dolomite for talc, up the amount of silica in a recipe and decrease the amout calcium carbonate, whiting, until the same equivalents are in the recipe as before. If substituting magnesium carbonate up the silica, but don't do anything to the calcium. If you know how to formulate glazes, this should be trivial. If you don't I would be more than happy to propose an adjuted recipe for you to try. Just post here or e-mail a favorite talc, glaze recipe and I'll take a stab at modifying it for you to try. It should act in every way the same as the original recipe because all of the elements will be the same, only from different sources. My e-mail address is montassocatyahoodotcom Please fix the at and dot. |
#3
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Talc!
I can formulate glazes. I was hesitant to use Magnesium because I cannot
even image the volume I would need for the equivalent. Dolomite does not work in the glazes that iis used because the calcium to magnesium ratio doesn't work. One of the glazes is Randy's Red (ours is Toby's but very similar). Toby's Red ^6 32 gerstly 30 flint 20 kona f4 14 talc 5 epk 15.15 RIO roughly goes to 32 gerstly 30 flint 20 kona f4 8 magnesium carb 15.15 RIO When this gets upped to 10000grams that is 800 grams of Magnesium Carb.... That strikes me as a huge volume but I may be remembering wrong. If you think this is worth the try, I will mix up a batch. Thanks, Donna If you think I can use magnesium to replace the talc, I will work with that. "Bob Eld" wrote in message et... "DKat" wrote in message ... The writing on the wall is that the University is not going to allow us to use Talc either in our glazes or our clays (how in the world you are supposed to find that out given the mix we have that has come and gone and the recycling done...). Our best glazes use Talc. What in the world can you do to substitute it especially given that I have used it to keep glazes from crazing and it is the only thing that worked. Donna Talc adds magnesium to glazes and is used as a flux in some low fire clay bodies to lower the maturing temperature and extend the firing range. It is primarily used in white hobby and school type modeling clays. I'm not sure what would substitute for it in a clay body, perhaps a frit or other prepared fluxing agent. Or, perhaps dolomite and silica could serve this purpose in a body. Talc is magnesium silicate and provides both magnesium oxide and silica to a glaze. Magnesium can be gotten fom dolomite which is a calcium, magnesium carbonate or from chemical magnesium carbonate. If substituting dolomite for talc, up the amount of silica in a recipe and decrease the amout calcium carbonate, whiting, until the same equivalents are in the recipe as before. If substituting magnesium carbonate up the silica, but don't do anything to the calcium. If you know how to formulate glazes, this should be trivial. If you don't I would be more than happy to propose an adjuted recipe for you to try. Just post here or e-mail a favorite talc, glaze recipe and I'll take a stab at modifying it for you to try. It should act in every way the same as the original recipe because all of the elements will be the same, only from different sources. My e-mail address is montassocatyahoodotcom Please fix the at and dot. |
#4
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Talc!
On Tue, 4 Dec 2007 14:28:02 -0500, "DKat"
wrote: The writing on the wall is that the University is not going to allow us to use Talc either in our glazes or our clays (how in the world you are supposed to find that out given the mix we have that has come and gone and the recycling done...). Our best glazes use Talc. What in the world can you do to substitute it especially given that I have used it to keep glazes from crazing and it is the only thing that worked. Donna So, what is the University's reason for this? Is the about the talc itself (magnesium silicate), or some impurity? Considering that baby powder is talc, and the way it is applied (through those shaker-top squeeze bottles) puts a lot of it into the air, compared to a potter stirring talc into a glaze, one has to wonder. Or is baby powder now an endangered species as well? Best regards, Bob Masta DAQARTA v3.50 Data AcQuisition And Real-Time Analysis www.daqarta.com Scope, Spectrum, Spectrogram, FREE Signal Generator Science with your sound card! |
#5
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Talc!
On Tue, 4 Dec 2007 23:38:51 -0500, "D Kat"
wrote: I can formulate glazes. I was hesitant to use Magnesium because I cannot even image the volume I would need for the equivalent. Dolomite does not work in the glazes that iis used because the calcium to magnesium ratio doesn't work. One of the glazes is Randy's Red (ours is Toby's but very similar). Toby's Red ^6 32 gerstly 30 flint 20 kona f4 14 talc 5 epk 15.15 RIO roughly goes to 32 gerstly 30 flint 20 kona f4 8 magnesium carb 15.15 RIO When this gets upped to 10000grams that is 800 grams of Magnesium Carb.... That strikes me as a huge volume but I may be remembering wrong. If you think this is worth the try, I will mix up a batch. Thanks, Donna I don't think you can use magnesium carbonate... the glaze will crawl off the pot and out of the studio! Best regards, Bob Masta DAQARTA v3.50 Data AcQuisition And Real-Time Analysis www.daqarta.com Scope, Spectrum, Spectrogram, FREE Signal Generator Science with your sound card! |
#6
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Talc!
Thanks Bob. I figured there had to be some reason Magnesium carb wasn't
being used. Nice to know before I invest the time. Donna "Bob Masta" wrote in message ... On Tue, 4 Dec 2007 23:38:51 -0500, "D Kat" wrote: I can formulate glazes. I was hesitant to use Magnesium because I cannot even image the volume I would need for the equivalent. Dolomite does not work in the glazes that iis used because the calcium to magnesium ratio doesn't work. One of the glazes is Randy's Red (ours is Toby's but very similar). Toby's Red ^6 32 gerstly 30 flint 20 kona f4 14 talc 5 epk 15.15 RIO roughly goes to 32 gerstly 30 flint 20 kona f4 8 magnesium carb 15.15 RIO When this gets upped to 10000grams that is 800 grams of Magnesium Carb.... That strikes me as a huge volume but I may be remembering wrong. If you think this is worth the try, I will mix up a batch. Thanks, Donna I don't think you can use magnesium carbonate... the glaze will crawl off the pot and out of the studio! Best regards, Bob Masta DAQARTA v3.50 Data AcQuisition And Real-Time Analysis www.daqarta.com Scope, Spectrum, Spectrogram, FREE Signal Generator Science with your sound card! |
#7
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Talc!
Apparently Ceramic Supplies (NJ) gets its talc from a mine in Connecticut
where the talc has been contaminated with asbestos. The University Environmental 'police' confiscated our talc and were going to take our glazes made with talc. They were talked out taking the glazes. I learned this morning that we are going to try to get a replacement talc from Texas... I keep on swearing I'm not going back into the studio yet I keep finding myself there. ..... Donnna "Bob Masta" wrote in message ... On Tue, 4 Dec 2007 14:28:02 -0500, "DKat" wrote: The writing on the wall is that the University is not going to allow us to use Talc either in our glazes or our clays (how in the world you are supposed to find that out given the mix we have that has come and gone and the recycling done...). Our best glazes use Talc. What in the world can you do to substitute it especially given that I have used it to keep glazes from crazing and it is the only thing that worked. Donna So, what is the University's reason for this? Is the about the talc itself (magnesium silicate), or some impurity? Considering that baby powder is talc, and the way it is applied (through those shaker-top squeeze bottles) puts a lot of it into the air, compared to a potter stirring talc into a glaze, one has to wonder. Or is baby powder now an endangered species as well? Best regards, Bob Masta DAQARTA v3.50 Data AcQuisition And Real-Time Analysis www.daqarta.com Scope, Spectrum, Spectrogram, FREE Signal Generator Science with your sound card! |
#8
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Talc!
"DKat" wrote in message ... Apparently Ceramic Supplies (NJ) gets its talc from a mine in Connecticut where the talc has been contaminated with asbestos. The University Environmental 'police' confiscated our talc and were going to take our glazes made with talc. They were talked out taking the glazes. I learned this morning that we are going to try to get a replacement talc from Texas... I keep on swearing I'm not going back into the studio yet I keep finding myself there. .... Donnna "Bob Masta" wrote in message ... On Tue, 4 Dec 2007 14:28:02 -0500, "DKat" wrote: The writing on the wall is that the University is not going to allow us to use Talc either in our glazes or our clays (how in the world you are supposed to find that out given the mix we have that has come and gone and the recycling done...). Our best glazes use Talc. What in the world can you do to substitute it especially given that I have used it to keep glazes from crazing and it is the only thing that worked. Donna So, what is the University's reason for this? Is the about the talc itself (magnesium silicate), or some impurity? Considering that baby powder is talc, and the way it is applied (through those shaker-top squeeze bottles) puts a lot of it into the air, compared to a potter stirring talc into a glaze, one has to wonder. Or is baby powder now an endangered species as well? Best regards, Bob Masta try baby powder on sale at walmart. read the label, as some baby powder is really corn starch. |
#9
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Talc!
"D Kat" wrote in message ... I can formulate glazes. I was hesitant to use Magnesium because I cannot even image the volume I would need for the equivalent. Dolomite does not work in the glazes that iis used because the calcium to magnesium ratio doesn't work. One of the glazes is Randy's Red (ours is Toby's but very similar). Toby's Red ^6 32 gerstly 30 flint 20 kona f4 14 talc 5 epk 15.15 RIO roughly goes to 32 gerstly 30 flint 20 kona f4 8 magnesium carb 15.15 RIO When this gets upped to 10000grams that is 800 grams of Magnesium Carb.... That strikes me as a huge volume but I may be remembering wrong. If you think this is worth the try, I will mix up a batch. Thanks, Donna If you think I can use magnesium to replace the talc, I will work with that. "Bob Eld" wrote in message et... "DKat" wrote in message ... The writing on the wall is that the University is not going to allow us to use Talc either in our glazes or our clays (how in the world you are supposed to find that out given the mix we have that has come and gone and the recycling done...). Our best glazes use Talc. What in the world can you do to substitute it especially given that I have used it to keep glazes from crazing and it is the only thing that worked. Donna It sounds like you have it in hand and can reformulate if necessary but with Texas talc or another source, that may not be necessary. I was trying to look at the molecular formulas and can't find, in this short time, a proper formula for Gerstly Borate, Some references are giving the formula for Colemanite under Gerstly but they are not the same. Furthemore, I understand the Gerstly mine has closed which means you may have to re-formulate anyway regardless of the talc issue. Thoughts? I will still play around with formulations as time permits and post them here. BTW, the above formula just replaces talc with magnesium carbonate but does not adjust the silica or the lime in the Gerstly. The silica and alumina balance is even worse because there is no kaolin. It would probably give very different results. |
#10
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Talc!
"charlie" ) writes:
"DKat" wrote in message - snips - ... Apparently Ceramic Supplies (NJ) gets its talc from a mine in Connecticut where the talc has been contaminated with asbestos. The University Environmental 'police' confiscated our talc and were going to take our glazes made with talc. They were talked out taking the glazes. I learned this morning that we are going to try to get a replacement talc from Texas... Donnna try baby powder on sale at walmart. read the label, as some baby powder is really corn starch. Talc occurs in association with asbestos. This is why most, if not all, baby powders are corn starch. Adult powders might be more likely to have talc. I'd imagine that any talc source could end up containing asbestos as they went from one end of the mine to the other. And like any sort of contamination, the government can change the allowable parts per million or whatever. The Canadian government is still trying to mine and sell asbestos as an insulation. It's doing this because there are great quantities of it in Quebec. But it generally* can't be sold in Canada and there are fewer and fewer takers because the stuff is so bad for the lungs. Elaine * my source says some precast concrete can have asbestos. |
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