opaque layer
The initial ceramic layer fired directly onto a metal or zirconia coping to mask its underlying color and create a foundation for subsequent dentine and enamel porcelain.
Full Definition
The opaque layer is the first porcelain application in a layered ceramic restoration. Its primary function is optical—blocking the gray or dark metallic hue of the substructure—while also forming the chemical and mechanical bond between metal oxide and overlying feldspathic porcelain. Opaque is supplied as a paste or powder and is fired at high temperature in a porcelain oven. Improper opaque coverage leads to color instability, commonly described as 'show-through' in laboratory reports. Editors must distinguish 'opaque layer' from 'dentine layer' and 'enamel layer,' which build the three-dimensional shade above it.
Usage
Usage note: Editors should retain the distinction between 'wash opaque' (ultra-thin first application) and 'opaque layer' (full coverage build-up); collapsing the two terms obscures technique details.
In Context
- "The shade mismatch was traced back to an insufficient opaque layer that allowed the base metal color to show through the final ceramic." — Laboratory Failure Analysis Report
- "A wash opaque is applied as a thin first coat before the full opaque layer is built up on the coping." — Ceramic Technique Manual