Sputty Posted March 19, 2017 Report Share Posted March 19, 2017 . Link to comment Share on other sites More sharing options...
Mark C. Posted March 19, 2017 Report Share Posted March 19, 2017 I have used Colemanite /gertsley boratefor over 4 decades-1st in Raku glazes then in high fire glazes./Cone 10 Its been a small % always and I have not had many issues with it although its composition has always changes and it been far from consistent. I read about all the woes but my take is most are at cone 6. I actually bought a ton of it (gertsley borate)when it was going to be taken off the market due to mine issues. I still have lifetime supply. I only have a few glazes that call for it and it alway as stated is in small amounts. I'm not a fan of Frits-only used them in Raku and low temp works.They settle like ground rocks. Link to comment Share on other sites More sharing options...
Marcia Selsor Posted March 19, 2017 Report Share Posted March 19, 2017 I use gertsley borate as a sub for Colemanite. I bought a lot of that when it was going to disappear. I have no problems with it even though it has a lot of complaints against it. Marcia Link to comment Share on other sites More sharing options...
neilestrick Posted March 20, 2017 Report Share Posted March 20, 2017 Test it out and see what you think. It may or may not be a problem. If needed, reformulate for whatever you have access to, be it Gerstley or Frit. Frits do not settle badly if you have a well formulated glaze with enough clay to keep it suspended. The problem is that a lot of old glaze recipes relied on Gerstley to keep the glaze suspended, which it does very well. So if you substitute a frit in those cases then you can have suspension problems. Link to comment Share on other sites More sharing options...
glazenerd Posted March 20, 2017 Report Share Posted March 20, 2017 I have been using Calcium Borate for a little over a year or so. Primarily produced from Turkish colemanite: 50% boron and 30% calcium (+/-): roughly twice the bang of gerstley borate. I started a thread about it back in Dec. 2015, and I seem to recall some posts about boron/calcium frits being mentioned. I have had no problems with it for cone 6 use: and I have used it (need to check this) up to 27% of batch weight. A borosilicate glaze with the right level of alumina can be highly abrasion resistant. I use I for a couple of floor tiles I make; I found it to be more durable, and a high satin sheen. Nerd http://community.ceramicartsdaily.org/topic/13318-calcium-borate/?hl=%2Bcalcium+%2Bborate Link to comment Share on other sites More sharing options...
Sputty Posted March 20, 2017 Author Report Share Posted March 20, 2017 . Link to comment Share on other sites More sharing options...
High Bridge Pottery Posted March 20, 2017 Report Share Posted March 20, 2017 I remember doing a bit of research into this after trying colemanite and it jumping off every pot. The only temperature I can find is 800c for getting rid of the chemical water. No idea if it will still be a powder after but melting temps seem around 1000~. Maybe you could just slow down a glaze firing through there. Digital fire also talks about the possibility of gypsum impurities. You could melt a load into your own frit Link to comment Share on other sites More sharing options...
Sputty Posted March 20, 2017 Author Report Share Posted March 20, 2017 . Link to comment Share on other sites More sharing options...
High Bridge Pottery Posted March 20, 2017 Report Share Posted March 20, 2017 Great video I remember reading that you melt whatever you need for making frits and then pour it from molten into water and that does most of the smashing up of the frit. No need for a ball mill. Could be wrong. Link to comment Share on other sites More sharing options...
Pieter Mostert Posted July 22, 2017 Report Share Posted July 22, 2017 I got some Colemanite a few months ago, and tried putting it through a bisque firing. It didn't melt, but it shrunk and formed a hard mass. Judging by the sheen on the lid and sides of the container it was in, some of the boron volatized. It took quite a bit of work to grind it down fine enough to pass through a 120# screen, using a mortar and pestle, and then I discovered it was slightly soluble. You can see the crystals that have formed inside the cup as the water evaporated. Link to comment Share on other sites More sharing options...
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