These 1 mm-sized crystals were found precipitated in a couple of gallons of glaze containing 85% Ferro Frit 3195. They are cubical, hard and insoluble. Why and how to do they form? Many frits are slightly partially soluble and the degree to which they are are related to the length of time the glaze is in storage, the temperature, the electrolytes and solubles in the water and interactions with other material particles present. The solute then interacts with other materials particles to form insoluble species that crystallize and precipitate out as you see here. These crystals can be a wide range of shapes and sizes and come from leaded and unleaded frits.
Pages that reference this post in the Digitalfire Reference Database:
Ferro Frit 3195, A glaze slurry precipitates flakes, Precipitate can forms in fritted glazes, remember to screen it, Precipitated crystals from a glaze having 60% lead bisilicate frit, G2925B glaze can precipitate crystals like this over time, Ooids in Glazes, Precipitation
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