Monthly Tech-Tip | No tracking! No ads! |
Dipping glazes peel like this because they contain clay and shrink as they dry (the fact that all of them don't do this is actually amazing). Success is a matter of the shrinkage being low enough, the drying being fast enough, the layer being thin enough, the bisque being absorbent enough, and the bond with the bisque being good enough. Glazes with high clay content, thick applications or multi-layering are the main offenders. Thixotropic slurries apply most evenly and are least likely to go on too thick. Dipping glazes having 15-20% kaolin or ball clay are easiest to slurry up and have the best application and drying properties. Mixing base layers as first-coat dipping glazes is also important.
The problem with this piece: The addition of 7.5% bentonite to make up for the otherwise low raw clay content in the recipe produced a recipe that does not pass a sanity check. When that was replaced with kaolin it worked. There is a crowbar approach to fix these without any other changes: Add CMC gum (e.g. 1%) to make them brushing glazes.
Glossary |
Glaze Layering
In hobby ceramics and pottery it is common to layer glazes for visual effects. Using brush-on glazes it is easy. But how to do it with dipping glazes? Or apply brush-ons on to dipped base coats? |
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