Salt and Soda Glazes

Salt and soda glazing are techniques where salt (plain table or rock salt) or soda (sodium bicarbonate) are dumped into the kiln during the firing process. Sodium from either the salt or the soda combines with materials on the surface of the pot to produce a glaze which is basically a sodium or sodium-aluminum silicate. While this is a very effective way produce a clear, hard, glazed surface, the process is not without difficulty. It not only results in glaze on the surface of the pot, but on the entire inside surface of the kiln. Kiln shelves and brick have a much shortened life when used for salt or soda firing. Salt firing has one other controversial aspect: a significant cloud of hydrochloric acid is emitted from the kiln for a few minutes after the salt is dumped. While a debate rages on as to whether the amount of HCl emitted is significant or not, my nose tells me to stay upwind from that cloud.