Gesso - Traditionally, a lean layer of size and chalk to form a ground on which to paint.
Ground - A layer of opaque paint applied to a support to provide a suitable color and texture on which to draw or paint.
Inpainting - Paint applied over losses only. This is a technique commonly used by conservators to unify a painting that has suffered paint loss.
Microenvironment - The environment of a very small, specific area.
Overpaint - This paint was not applied by the artist but applied at a later date. It not only covers the original paint, but its presence often indicates an excessive alteration of the image. Overpainting is not an acceptable conservation technique.
Retouching - The work done by a restorer to replace areas of loss or damage in a painting.
Varnish - An applied surface film, usually of a transparent, cloudless resin. It imparts an even gloss to the surface, wetting the paint, and providing protection for it.