alli Posted March 12, 2021 Report Share Posted March 12, 2021 I recently purchased a clear glaze to use over underglazes but completely forgot to look for zinc free. Will applying the underglaze before bisque firing keep them in place or will the zinc still make bisqued colors bleed? Link to comment Share on other sites More sharing options...
Bill Kielb Posted March 12, 2021 Report Share Posted March 12, 2021 Any of your underglazes that are affected by zinc will be affected in the glaze firing so bisque firing your underglaze first is unlikely to save them. Not all colors are affected equally so check with your underglaze manufacture. Link to comment Share on other sites More sharing options...
Dick White Posted March 13, 2021 Report Share Posted March 13, 2021 The zinc-free issue is not about the underglazes bleeding, but rather it is about an undesirable color change when the underglaze contains chrome oxide as a colorant - which is quite a few of them. Zinc is a useful flux agent in some glazes, but does not play well together with chrome. Thus, a clear glaze that does not have any zinc in it is necessary for any chrome-tinted underglaze. Link to comment Share on other sites More sharing options...
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