What is the cause of an oil painting getting progressively duller as layers are added?
This is called ‘sinking’ and is a result of the ground or underlayer being too absorbent. If the sinking is consistent over a large area then this would indicate the ground is too absorbent. This is common when household emulsion is used for a primer. Artists’ primer properly applied on your next canvas will be less absorbent. However, when building up oil colour in layers, the different drying rates can also result in a paint film with varying absorbency. This is usually indicated by dull spots rather than complete dull areas. In either case, dull areas must be treated, or as you have found, any further layers will only continue to sink. The absorbent areas are drawing the oil from any fresh colour which is applied. Dull areas should be ‘oiled out’ using Artists’ Painting Medium from Winsor & Newton. Rub this sparingly into the affected areas and leave to dry. This is a stand linseed oil/white spirit mixture. Repeat as necessary if any smaller patches remain.
