Soda glazing generally takes place during the firing, rather than being applied beforehand. Soda ash (sodium carbonate) is sprayed in a liquid solution into the kiln for prolonged periods of time. The soda vaporises and is carried through the kiln chambers by the flames, landing on pot surfaces as the fire comes into contact with them and creating varied ‘pitted’ effects similar to salt glazes.
The interaction between soda and pot can be anticipated by applying different slips - mixtures of water and clay - or glazes to the pots before firing. The soda vapours landing on the slips combine with silica in the clay to create dramatic oranges and yellows and deep blue glasses.
Lisa Hammond has been championing the method for some time now and her soda glazed pots rank among the world’s finest.