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subject: salt glazed problems

updated fri 30 nov 07


Ivor and Olive Lewis on thu 29 nov 07

Dear James O. Kenney

The first thing I would wish to clarify would be "Why are you salt =
glazing clay that is covered with a conventional glaze ?"

Grey or bleached clay might be attributed to excessive reduction. It may =
also be due to your kiln being exceptionally hot during the application =
of salt.

Dark brown suggests reoxidation of an iron bearing clay during cooling.

As far as I know the distinction between Rock Salt and "Softener Salt" =
is one of refinement. Rock salt is a natural mineral, the other is the =
residue of Sodium chloride after refining has removed Potassium and =
Magnesium chlorides.

If you have not yet read Jack Troy, "Salt Glazed Ceramics" you should =
and follow up on his reference to Barringer, "The relationship between =
the constitution of a Clay and its Ability to take a good Salt Glaze"

By the way, if you are able to do the thermodynamic calculations it is =
not difficult to show that the popular way of explaining Salt Glaze =
Chemistry would be untrue.

Best regards,

Ivor Lewis.
South Australia.