I recently moved a large amount of oil paintings cross country in a trailer. They were stacked vertically, but a couple of paintings that were leaning face-to-face ended up transferring paint from one to the other (see attached photos). The underlying paint seems undamaged, it seems color from one painting just transferred across. These are not fresh paintings, all were painted at least a decade ago so the paint should be completely dried and cured. Transfer happened in the past couple of days, so I'd like to take care of it hopefully before it has a chance to set.
What methods would you recommend I try to remove the transferred color?
- Water based?
- Mild detergent?
- Any mild solvents I should try?
- Gentle bristle brush work, or soft rag?
So far I haven't tried anything, this might be easy, but I'm looking for suggestions that are likely to be effective but not damage the paintings.