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This is a cone 6 transparent base glaze. It contains frit, silica, kaolin, wollastonite. Almost all glazes have materials that are slightly soluble and over time these can form scale on the sides of the bucket or even precipitate particles into the slurry. The defects here are those scales. Before dipping a production piece in any glaze that has been in storage it is a good idea to assess it first to see if it needs to be sieved.
The glaze defects are caused by precipitates that have formed in this glaze slurry within days of batching it. They are refractory and do not dissolve in the glaze melt - creating a defect that is unrepairable. In industry, glazes are batched and sieved as an ongoing process but in pottery and hobby ceramics they are stored for months or even years after batching. It is normal to have to sieve these slurries every few months but in recent years the precipitates form more quickly. Frits are theoretically insoluble, but in practice, they are not. Frit quality is determined not just by careful control of the chemistry but also of the smelting, mixing and water-quenching processes.
Glossary |
Precipitation
Crystals or crystalline particles will often form over time in ceramic glaze slurries that contain slightly soluble materials. |
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Glossary |
Sieve
Sieves are important in ceramics for removing particulates and agglomerates from glaze, engobe and body slurries. |
Glossary |
Base Glaze
Understand your a glaze and learn how to adjust and improve it. Build others from that. We have bases for low, medium and high fire. |
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