I applied modern oil base paint over older lead oil base paint and I am finding areas where the new oil base paint is peeling. What is causing this?
The old oil base paint is very hard. This is a difficult surface for the new paint to stick to.
In the future; to help the new paint stick buy some liquid sander/deglosser and wipe all surfaces before painting. This will chemically etch the surface, improving adhesion. Paso Liquid Sander is the best for this, in my opinion.