search  current discussion  categories  kilns & firing - salt & soda 

salt galze problems

updated sat 29 dec 01


iandol on fri 28 dec 01

Dear Vivek Patel <>

Although I have not seen your pictures I offer the following =

Most Salt Glazes surfaces are crazed, so what you are experiencing is =
normal rather than unusual. Often the crazing is extremely fine in =
texture and is not noticed unless the glaze is thick and transparent.

I think if you can get into the industrial ceramic archives of the =
American Ceramics Society you will find that some producers in the past =
augmented their salt, that is Sodium Chloride, by incorporating a =
proportion of Boric acid or Borax into the mixture before baiting the =
kiln. The addition of a small proportion of Boron can help to change the =
Coefficient of Thermal Expansion of the surface coating which develops =
when common salt reacts with the clay body and is thought to reduce the =
incidence of crazing..

Do you know the mineral composition of your Black Fireclay or the =
origins of your Grog? Do you know the chemistry of your felspar? What =
cone are you salting at?

Best regards,

Ivor Lewis. Redhill, South Australia