Pres Posted May 22, 2015 Report Share Posted May 22, 2015 bruce, i am sorry that i do not read chemical formulas. please, what does this really mean in ordinary terms? just in case Bruce doesn't see this I'll jump in. In ordinary terms Roy reformulated it and his version was tested for cobalt leaching and Hesselbreth says it should be okay for functional pots. The main change Roy made was decrease the cobalt and add a titch of strontium. Roy's recipe as on the link Bruce posted is: Ferro Frit 3134............. 37.00 Custer Feldspar............. 16.00 Strontium Carbonate......... 4.00 EP Kaolin................... 26.00 Silica...................... 17.00 Cobalt Carbonate............ 2.50 Rutile...................... 4.50 ========= 107.00 I'm in stitches over a titch of Strontium! Link to comment Share on other sites More sharing options...
Celia UK Posted May 22, 2015 Report Share Posted May 22, 2015 Cobalt Carbonate when fired turns into Cobalt Oxide and Carbon Dioxide. The same way that we use Calcium Carbonate to add Calcium Oxide you can use Cobalt Carbonate to add Cobalt Oxide. 'The theoretical oxide form has 93% CoO while the carbonate has 63%. So if you want to switch from the oxide to the carbonate in a recipe, multiply by 93 and divide by 63. To switch from carbonate to oxide multiply by 63 and divide by 93.' Joel - I just love these technical glaze chemistry posts despite the fact that they make me realise how much you know that I never will! Oh to be young again.......... Link to comment Share on other sites More sharing options...
Babs Posted May 22, 2015 Report Share Posted May 22, 2015 Knew a potter who "blessed " many of her glazes with a pinch,( not snitch, or was that titch), of Rutile.... Can only get away with this level of science when you know what you're doing. Or perhaps she had a heap of rutile she was trying to use up before departing the planet, I don't think so though. Link to comment Share on other sites More sharing options...
oldlady Posted May 23, 2015 Author Report Share Posted May 23, 2015 well, after all these days, the plate with the vinegar test appears to be unaffected by that acid. good news! i think i will wash it and use it for french toast with a titch of maple syrup. guess what? spellcheck doesn't raise an eyebrow over titch. Link to comment Share on other sites More sharing options...
Babs Posted May 24, 2015 Report Share Posted May 24, 2015 you spelt it correctly that is why.. doesn't like spelt! old fashioned form of have spelled?? Link to comment Share on other sites More sharing options...
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