I ran into a problem yesterday I am hopng someone with more experience can prevent in the future. I am a carpenter - not a painter. I did a drywall repair job, a section about 2 ft. x 3 ft. high under a built-in cabinet. Spacked and sanded it. It was to be painted blue to match the existing room. I didn't have any primer, so I covered the bare drywall and spackle with a coat of contractor's grade laytex eggshell white I happened to be using for another project. So far, so good. I let it dry for 24 hours. The white finish looked nice. I rolled on the blue laytex semigloss on top of the white. It went on fine except for one area where the "primer" bubbled under the new paint. I went to pull off the bubble and a large piece of white paint came completely free of the drywall, it was as if it was never there. As I tryed to clean up the edges more and more came off. I ended up with a spot about 6" square that looked like it was never painted. And I couldn't roll the finish coat over the bare spot since the roller just kept taking more paint off. I was able to finish the job with a brush and a light touch. And since it was mostly hidden under a cabinet it looked OK but not professional by any means. But what did I do wrong?