Treatment of The Triumph of the Winter Queen: Allegory of the Just, dated 1636, by Gerrit van Honthorst (Dutch, 1590–1656):
July 2012

With all the losses filled, the painting is given an initial brush coating of varnish in order to saturate the surface and isolate the original paint from the retouching materials to come. A natural resin varnish, similar to what Honthorst would have used, is selected to match the appearance of the original surface as closely as possible.

With tiny watercolor brushes, conservators inpaint the areas of loss using Gamblin Conservation Colors, which are made of chemically inert and light stable pigments ground in a synthetic resin. The Colors help to distinguish the new paint from the original, since the retouching materials dissolve in solvents that won’t affect the original oil paint.

Below are before and after details showing the transformation of the painting after retouching.
Gustavus Adolphus and the lions:

Neptune's leg: