Surfaces and Finishes

Surface choices change how a sculpture reads under light: matte or glossy, one color or many, smooth or textured. The terms below are studio standards. Recipes and food-safety ratings are specific to products and firings — check labels.

Slip

Slip is clay mixed with water to a liquid. Extension materials describe it as the “glue” for scored joins and as a decorating coating. Colored slips and engobes can be brushed or trailed onto damp or leather-hard clay.

Underglaze

Underglazes are colored coatings usually applied to greenware or bisque and often covered with a clear glaze. Bellevue College’s chart notes that many commercial underglazes are intended for mid-range use and lists a maximum related to cones 4–6 for many Amaco and similar products — read each bottle.

Glaze

Glaze is a glass-forming coating melted onto ceramic in a firing. Low-fire, mid-range, and high-fire glazes must match the clay’s mature range. Clear, opaque, matte, and gloss finishes are all glaze options. Unglazed sculpture can still be finished by burnishing, terra sigillata, or leaving the fired clay bare.

Oxides and stains

Metal oxides and commercial ceramic stains tint slips, clay, and glazes. They are handled as studio chemicals with dust controls. This page does not list oxide percentages.

Texture without glaze

Stamping, impressing fabric or found objects, carving, and thick slip texture are common on sculpture. The older CeramicSculpture.com homepage noted that fabric with a nap can be pressed into damp clay — a standard impressing idea when clay is soft enough to take a print.

Sources

• Colorado State University Extension, Ceramics Unit 1 (PDF)
• Bellevue College, Firing Temperatures & Cone Equivalents (PDF)
• Colorado State University Extension, Ceramics Unit 7 — Sculpture (PDF)