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a new twist to salt emissions

updated wed 21 jun 00


iandol on mon 19 jun 00

A new twist to salt emissions ?

I understand it is a common belief that glazes which are high in Sodium =
oxide are notorious for crazing. Therefore, as a general principle, =
glazes are formulated to avoid this defect and to do this the group I =
alkalies are kept to as low a proportion as possible. But no one ever =
says, stop, think, do glazes made by salt or soda glazing craze? Do some =
dye penetration testing and you will find examples of salt glazed pots =
which are crazed.=20

Yes, residual salt evaporates from the fire boxes a kiln is heated. Some =
may diffuse into immature porous clay. This could play havoc with body =
maturity through over fluxing. Also, if the clay is undercooked and =
porous and the final glaze is crazed, salt could leach out of the pot. I =
have been told of saltglaze mugs which tainted coffee.

Ivor Lewis.