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Raymond P.

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  1. Hi Dick, Thanks a lot for your valuable comments and recommendation, which I will follow. I will run some test this time (should have done it earlier!).
  2. CaO should read CaCo3 (craie in French)
  3. Hi Bill. The base recipe is a slight variation from one from my ceramic classes 25 years ago. I increased Ti ox from 3% to 5% (for opacity?) and reduced CaO from 18% to 14 % (hoping to increase brillance). The colorant addition were also from old (successful) recipes. Both colours had been Ok years ago, but with different bases. Note that I resumed my ceramic experiments after a 25 year gap. I have probably forgotten a lot. Thanks for helping.
  4. I prepared a base: Kalifeldspath 39gr, Colemanite 3 gr, Dolomite 5 gr, CaO 14 gr, Titanium oxyde 5 gr, Kaolin 4 gr, Silica 30 gr. To one half I added the following: Cobalt carbonate 4.5%, Rutile 3.0 %, FeO3 0.15%, Zirconium Oxyde 2.5%. At 1205˚C this produced a nice, smooth & shiny blue glaze, as expected. To the othe half I added 0.5% Cr oxyde and 2.0% Sn oxyde. At the same temperature, in the same run, the résult was catastrophic. Purple color, as expected, but it did not melt well, and did not stick to the pieces. Shreds of galze were hanging from the pieces.See attached .pdf . Any explanation? Has it to do wit the presence of Cr? Cr problems .pdf
  5. Thank you Bill, Johnny and Peter for your valuable input. It does not react with acid. As I had only 2 Kg of it, I got rid of it (responsibly!).
  6. I lost the label of a product in my supplies. It looks and feels like limestone (chalk), which I thought it was. I have put some in the bottom of my kiln (to avoid adherance of my stuff), but it melted (at 1115 ˚C). Imagine the disaster. Any idea what it can be? Thanks. Raymond
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