It is then usually placed in a bed of combustible materials and covered, creating intense reduction resulting in irregular surfaces and colors. What would have been copper oxide in an oxidation atmosphere will be pure copper in reduction. Reduction allowed the Chinese to develop the sangue de beouf red glazes and gives Raku its metallic finishes. Slab Built Clay slabs are cut to shape and joined together using scoring and wet clay called slip. Slabs can be draped over or into forms, rolled around cylinders or built-up into geometric forms.
Large forms are difficult because of stresses on the seams and because the slab naturally sags.
Some potters get around this by working fibers into the clay body. The fibers burn out during the firing, leaving a network of tiny holes. A fine, liquid form of clay applied to the surface of a vessel prior to firing. Slip fills in pores and gives uniform color. A high-fire clay.