I’m currently working on a lovely portrait from the early 20th century that has extensive drying cracks. Although drying cracks can be quite alarming to look at they are usually completely stable. They occur when the upper paint layer dries more quickly than the one below, which means that as the wet layer underneath shifts as it dries the upper layer is pulled apart. Sometimes drying cracks aren’t particularly problematic but in this case a lot of white is showing in a black field of colour. When a paint layer is damaged your eye is drawn to the damage rather than seeing the subject, so I’ve been retouching the widest of the drying cracks to give some solidity to the forms. The medium I’m using for retouching has completely different solubility parameters to the original paint, which will make it reversible in the future if necessary.