Callie Beller Diesel Posted July 8, 2020 Report Share Posted July 8, 2020 @liambesaw Should have known better! Thank you. Link to comment Share on other sites More sharing options...
Bill Kielb Posted July 9, 2020 Report Share Posted July 9, 2020 On 7/6/2020 at 9:54 AM, Benzine said: I am glad I have never had to deal with any materials that were overly toxic. I have some glazes that I inherited that do contain lead. I pulled them from student use, mixed them together and have been gradually coating "leftover" pieces in it, firing them, then tossing in the trash. Careful, lead often collects on the bricks of the kiln during firing. I would just dispose of in appropriate fashion as hazardous waste and not fire them. School should have an account for such waste products, very common. Link to comment Share on other sites More sharing options...
Min Posted July 9, 2020 Report Share Posted July 9, 2020 Frank Hamer goes into the decomposition of BaCO3 to BaO needing a reducing atmosphere at a minimum temp of 1650F in his Potters Dictionary, link to relevant snippet here. It's interesting what he says about BaCO3 insofar as if it doesn't get decomposed to the oxide it then acts as an anti-flux and opacifier. Link to comment Share on other sites More sharing options...
liambesaw Posted July 9, 2020 Report Share Posted July 9, 2020 44 minutes ago, Min said: Frank Hamer goes into the decomposition of BaCO3 to BaO needing a reducing atmosphere at a minimum temp of 1650F in his Potters Dictionary, link to relevant snippet here. It's interesting what he says about BaCO3 insofar as if it doesn't get decomposed to the oxide it then acts as an anti-flux and opacifier. Yes, in mid fire oxidation it serves to opacify and matte, but it's the bad kind of matte which is underfired. It never changes from barium carbonate because it first needs to ditch an oxygen atom in order to liberate it's co2 I personally will leave the job of engineering glazes with barium to industry experts and definitely not from glaze recipe books. I don't get paid enough! Link to comment Share on other sites More sharing options...
allenc27 Posted October 10, 2020 Author Report Share Posted October 10, 2020 On 7/1/2020 at 5:41 AM, liambesaw said: Here's why barium is not recommended. If barium is fired without carbon monoxide, it doesn't enter the glaze melt. Instead it acts as an opacifier and stays outside of the melt. When it is underfired or fired in oxidation, it leaches barium oxide which is... That's right! Toxic! And most barium glazes are oxidation cone 6 glazes that use the barium as a refractory/matting agent or opacifier. Which is exactly the wrong application. It's one of those ingredients that when properly used by industry, are invaluable. But when left to the hands of hobbyists and craftsmen, it's better to avoid it altogether. Same with lead oxides. Lead is still used by the dinnerware industry in their glazes, but it's engineered to be done safely. I don't see anyone recommending people use lead in their glazes because it can be done safely, so why barium? How about cadmium, is there an acceptable limit to that? Vanadium? Uranium? Yes there are! But not for everyone. Do you mean if I fired at cone 10 reduction then it wouldn't be toxic as functional ware? Link to comment Share on other sites More sharing options...
Babs Posted October 10, 2020 Report Share Posted October 10, 2020 Not as a liner, bottom 2 thirds of outside of pots but would need to be tested . Link to comment Share on other sites More sharing options...
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