Saggar atmosphere, or concentrate the effects of salts, metal oxides and other materials on the surface of their ware. Some pots may be carefully prepared for saggar firing. One method creates a smooth surface covered with clay slip, terra sigillata, which responds particularly well to the saggar technique. This slip covering may be burnished to achieve a gloss. Prepared pots are nestled into saggars filled with beds of combustible materials, such as sawdust, less combustible organic materials, salts and metals. These materials ignite or fume during firing, leaving the pot buried in layers of fine ash. Ware produced in filled saggars
Saggar were expected to last for about 40 firings; each potbank made their own in a saggar making workshop. Saggars were made from fireclay, by a "saggar maker" and two assistants: the "framemaker" and the "bottom knocker". The framemaker beat the clay into a sheet on a metal table using a large mallet, the "mow" or "mawl". Using a "frame" he would cut it to size, sprinkle it with "sawdust" and wrap it round a wooden block to make the walls. The framemaker was usually an apprentice in his late teens. The bottom knocker, usually a boy in his early teens,