Any glaze process where the glaze results from vapor deposited within the kiln—includes salt glazing, soda glazing, fuming and wood firing (where fly ash is deposited on the ware and melted into a glaze).
Source:
Clay: A Studio Handbook
Vanadium Pentoxide
V2O5—weak yellow colorant—toxic, expensive—usually fritted with tin to produce stronger yellow. Highly toxic in inhalation and ingestion.
Source:
Clay: A Studio Handbook
Underglaze Engobe
Colored slips formulated to have low drying shrinkage, allowing application to bone-dry or bisque-fired surface before glazing. Commercial underglazes are available in a wide palette of colors primarily for low-fire, but many will survive high-fire.
Source:
Clay: A Studio Handbook
Underglaze Decoration
Process of applying any decoration to the bare, (usually bisque-fired) clay surface directly before glazing.
Source:
Clay: A Studio Handbook
Undercut
Common flaw in plaster or bisque molds, where the clay or casting catches and will not pull free without breaking or distorting.
Source:
Clay: A Studio Handbook
Ultrox
Zircon opacifier. Toxic in inhalation.
Source:
Clay: A Studio Handbook
Trimming
At the leather-hard stage, removal of excess clay from a piece, using any of a variety of sharp cutting tools.
Source:
Clay: A Studio Handbook
Triaxial Blend
Method for testing three-way combinations of glaze materials, where proportional amounts vary through a series of samples between three limits. May involve change in glaze materials, or addition of colorants or modifiers.
Source:
Clay: A Studio Handbook
Tombo
A T-shaped Japanese throwing gauge, used to measure the depth and rim diameter of a vessel, usually when throwing off the hump.
Source:
Clay: A Studio Handbook
Titanium Dioxide
TiO2—matting/opacifying agent. Promotes crystal growth, visual texture in glazes.
Source:
Clay: A Studio Handbook
Tin Oxide
SnO2—most powerful opacifier, but expensive—inert dispersoid in glaze melt—5–7% will produce opaque white in a clear glaze. Toxic in inhalation and ingestion.
Source:
Clay: A Studio Handbook
Thermocouple
Temperature probe that produces minute variable electrical current dependent on degree of heat exposure—used in pyrometers and Baso valves.
Source:
Clay: A Studio Handbook
Thermal Shock
Effect of sudden temperature changes during firing or during subsequent heating and cooling in daily use.
Source:
Clay: A Studio Handbook
Thermal Expansion
The physical expansion and contraction that accompanies the heating and cooling of most materials. See coefficient of expansion.
Source:
Clay: A Studio Handbook
Terra Cotta Clay
Low temperature, porous earthenware clay body, fires red-brown due to high iron content, which also fluxes clay, making it the most durable low-fired clay after firing.
Source:
Clay: A Studio Handbook
Terra Sigillata
Ultra-refined clay slip that can give a soft sheen when applied to bone-dry wares and if polished or burnished while still damp may give a high gloss.
Source:
Clay: A Studio Handbook
Tenmoku
Classic East Asian high-iron gloss glaze giving black where thick, breaking to brown or red-brown where thin.
Source:
Clay: A Studio Handbook
Suspension
A liquid mix where insoluble particles are distributed throughout without dissolving and may settle out from gravity, as in a glaze or slip.
Source:
Clay: A Studio Handbook
Superpax
Zircon opacifier. Toxic in inhalation.
Source:
Clay: A Studio Handbook
Strontium Carbonate
SrCO3 Alkaline earth, high-temperature flux, similar to barium, slightly more powerful.
Any glaze process where the glaze results from vapor deposited within the kiln—includes salt glazing, soda glazing, fuming and wood firing (where fly ash is deposited on the ware and melted into a glaze).
Source: Clay: A Studio Handbook
V2O5—weak yellow colorant—toxic, expensive—usually fritted with tin to produce stronger yellow. Highly toxic in inhalation and ingestion.
Source: Clay: A Studio Handbook
Colored slips formulated to have low drying shrinkage, allowing application to bone-dry or bisque-fired surface before glazing. Commercial underglazes are available in a wide palette of colors primarily for low-fire, but many will survive high-fire.
Source: Clay: A Studio Handbook
Process of applying any decoration to the bare, (usually bisque-fired) clay surface directly before glazing.
Source: Clay: A Studio Handbook
Common flaw in plaster or bisque molds, where the clay or casting catches and will not pull free without breaking or distorting.
Source: Clay: A Studio Handbook
Zircon opacifier. Toxic in inhalation.
Source: Clay: A Studio Handbook
At the leather-hard stage, removal of excess clay from a piece, using any of a variety of sharp cutting tools.
Source: Clay: A Studio Handbook
Method for testing three-way combinations of glaze materials, where proportional amounts vary through a series of samples between three limits. May involve change in glaze materials, or addition of colorants or modifiers.
Source: Clay: A Studio Handbook
A T-shaped Japanese throwing gauge, used to measure the depth and rim diameter of a vessel, usually when throwing off the hump.
Source: Clay: A Studio Handbook
TiO2—matting/opacifying agent. Promotes crystal growth, visual texture in glazes.
Source: Clay: A Studio Handbook
SnO2—most powerful opacifier, but expensive—inert dispersoid in glaze melt—5–7% will produce opaque white in a clear glaze. Toxic in inhalation and ingestion.
Source: Clay: A Studio Handbook
Source: Clay: A Studio Handbook
Effect of sudden temperature changes during firing or during subsequent heating and cooling in daily use.
Source: Clay: A Studio Handbook
The physical expansion and contraction that accompanies the heating and cooling of most materials. See coefficient of expansion.
Source: Clay: A Studio Handbook
Low temperature, porous earthenware clay body, fires red-brown due to high iron content, which also fluxes clay, making it the most durable low-fired clay after firing.
Source: Clay: A Studio Handbook
Ultra-refined clay slip that can give a soft sheen when applied to bone-dry wares and if polished or burnished while still damp may give a high gloss.
Source: Clay: A Studio Handbook
Classic East Asian high-iron gloss glaze giving black where thick, breaking to brown or red-brown where thin.
Source: Clay: A Studio Handbook
A liquid mix where insoluble particles are distributed throughout without dissolving and may settle out from gravity, as in a glaze or slip.
Source: Clay: A Studio Handbook
Zircon opacifier. Toxic in inhalation.
Source: Clay: A Studio Handbook
SrCO3 Alkaline earth, high-temperature flux, similar to barium, slightly more powerful.
Source: Clay: A Studio Handbook