Low-Fire Salt-Glazing

The purpose for this research was to investigate the feasibility of using rock salt for glazing a clay body at pyromatric cone 04 (1940°F). Four clay bodies were used to see which reacted best with salt at cone 04. Experimentation with additions of borax to the salt were used to see how they effect the covering qualities of each body, as well as how they effect body color. Engobes used in the tests had different amounts of coloring oxides mixed with clay body number one and water. Colors ranging from light blue, green, and different hues of brown were achieved. Two types of salt-glazing mixtures were used in this investigation of low fire salt-glazing; one was one part borax, two parts rock salt, the other was 100% rock salt. The addition of the borax to the salt gave a thick shiny coat of glaze while the 100% rock salt gave the orange peel texture the author was looking for. Two kilns were built for this investigation. The first kiln was a small down-draught made of common soft brick. This kiln did not work because the common soft brick could not withstand the corrosive action of the salt vapor. The second kiln was a small tunnel kiln built of soft brick with a hard fire brick liner. This was the kiln used in all the successful tests made with the four bodies and engobes. The author is not stating that low-fire salt-glazing is superior to high fire salt-glazing but that it can be done. It opens up the possibility of salt-glazing to potters not having materials for a high fire kiln and shows that low fire salt-glazing can be done with a great savings of time and energy