ArtbyMarioOlmos Posted April 8, 2016 Report Share Posted April 8, 2016 Not sure how this happened. I am a ceramic student at a Community College, so the kiln is collective and I didn't loaded. I was using the glaze Mirror Black over a piece that was already bizqued with black engobe, and this is the result. I did ask my teacher, but not a clear answer. Any idea? Thanks! Link to comment Share on other sites More sharing options...
neilestrick Posted April 8, 2016 Report Share Posted April 8, 2016 It could be incompatibility with the black engobe. Could be the glaze is too thick. Could be the kiln was too hot/cold. Did any other pieces have problems? Have you used the glaze with the engobe before? Link to comment Share on other sites More sharing options...
High Bridge Pottery Posted April 8, 2016 Report Share Posted April 8, 2016 I think the black on black may have oversaturate the glaze with colouring oxides and given you that burnt toast look. Link to comment Share on other sites More sharing options...
Benzine Posted April 8, 2016 Report Share Posted April 8, 2016 The only time, I've seen something like that, is when I did a Raku firing and the wares didn't get hot enough. The glaze was boiling, but didn't have a chance to smooth out, before we pulled them out. I can't say for sure, that's what the problem was, but that's what it reminds me of. Link to comment Share on other sites More sharing options...
glazenerd Posted April 8, 2016 Report Share Posted April 8, 2016 Looks like molten glaze soup to me. I ran extensive flux tests a few years back: and will venture a semi- think I know guess. Potassium and sodium fluxes become gases at high temperatures, unlike lithium and calcium that are liquid. At cone 6 they boil, like what I see above. At cone 8, there is less of a boiling look: but a series of heavy pin holing. At cone 10, pin holing that most of us have seen. Without additional info, I can only venture a guess. Potassium causes more problems at cone 6 and sodium causes more problems at cone 10: from my experiments with them. Regardless, the boiled look is highly molten fluxes boiling and off gassing. IMO Not sure an extended hold would solve this problem: suspect the sodium/potassium batch % are well over 5.00% and probably closer to 6% ( or more). Nerd By the way: commercial clay or mixed in house? Link to comment Share on other sites More sharing options...
Magnolia Mud Researdh Posted April 8, 2016 Report Share Posted April 8, 2016 It looks like a cone 10 shino glaze over a cone 10 temoku glaze fired in reduction. LT Link to comment Share on other sites More sharing options...
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