Inpainting losses and abrasion is accomplished with dry pigments brush-ground in a stable, non-discoloring synthetic medium. The thin, transparent layers of inpaint are applied to the losses with tiny watercolor brushes.
The conservators match colors by eye. In a complicated, large area of loss, scores of colors may be applied to create the allusion of 17th century paint. Inpaint is limited to within the boundries of the losses in the painting.
The use of modern dry pigments and a synthetic paint medium is intentional. The synthetic resin does not change chemically with aging, remaining soluble in very mild solvents. In addition, the new materials are easily detected by another conservation professional. Importantly, the new fill and inpainting are isolated from the original paint layer by a synthetic resin varnish.