Oiling out is the application of an oil medium to a painting which has sunk (become dull), or lost its oil to the layer underneath. The most common causes for this are an over- absorbent, cheap ground or the use of too much solvent and insufficient or no medium. When the colour is dry, Artists’ Painting Medium should be sparingly rubbed into any sunken areas with a clean cloth.
Wipe off any residue and leave to dry for a day or two. If smaller, dull areas remain, repeat the process until the painting has regained an even sheen. Varnishes should not be used for the purpose of recovering the lustre of a dead painting. For a faster drying oiling out medium, use Thickened Linseed Oil diluted with 50% white spirit (mineral spirits).