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tanjag

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  1. Just found an incredibly helpful paper investigating historical shell tempering techniques, with tests using crushed oyster shells (pre fired and not) in the clay body, with variables including reduced atmosphere firing and varying temperatures. Verdict: pre-firing shells not important for integrity of final vessel, but reduced atmosphere firing OR keeping firing temp below 650C/1200F are important for a serviceable vessel. Seemed worth including here should anyone in the future go down this rabbit hole. https://www.jstor.org/stable/40713455
  2. Yes -- very helpful -- thanks!
  3. Marcia, this is also very useful info for me as I am experimenting with using the shells as temper in the clay body. I had not heard about the soaking post-kiln and will try that. Using preheated/roasted shells in the clay body apparently has quite a bit of historical precedence, but it is unclear to me how essential the preheating is, unless the temp is very high (at 500-600C the CaCo3 releases its CO2 and leaves CaO or calcium oxide/lime). Still looking into that one. More tests!
  4. Dick, Thanks -- that is a really useful starting place for me -- a much simpler recipe than I have found on my own. Question: If I added the zircopax, what ingredient should I start off trying to substitute (Ferro Frit 3195, EPK kaolin, or Whiting)? Yes -- will do many tests!
  5. New to ceramics and just learning about glazes. I am using found clay to make earthenware sculptures that I am firing at 06 (and which can withstand temperatures up to 02 before melting). I want to use ground up oyster shells (essentially CaCo3, or whiting) in the glaze for these pieces. The use of the oyster shells is conceptually related to the project i.e. they must me an ingredient in the glaze. I would like the glaze color to be light grey to white in color and preferably on the glossier side. Translucent to opaque is fine. I am not terribly concerned with perfection in the glaze (crazing, bubbles, unevenness are almost desirable) as long as the glaze adheres to the earthenware and doesn't easily flake/crack off. Where would I begin finding/creating a recipe for such a glaze? I have done my reading research on glazes but have never mixed a glaze myself. Any and all advice much appreciated. Thank you!
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