I am trying to refinish a les paul copy. Did a bad refinish way back when. I stripped it with chemicals, sanded it down, wiped it down with mineral spirits, stained it and did a black sunburst, using a technique I found on this site. Everything looked great, but when I started putting the first round of polyurethane on it I noticed that I could see the sanding marks in it. I went from too coars to too fine in one step. This was a day or two after putting the polyurethane on it, so I just grabbed the mineral spirits and stripped the front down again (the back seemed fine). I resanded, stained, and did my sunburst again. I got my first coat of poly on there and everything seemed fine. I waited about 6 days, sanded with fine/ultra fine wiped it down with tack cloth, and a quick wipe down with a damp rag and started in with the 2nd round of poly. After about 45 minutes or so, I went in for another coat and I noticed a couple of spots where it looked like the poly was bubbling up along the edges. I sprayed the 2nd round, hoping this might be something I could sand out of the final finish, but when I came back about another half hour or so later, much to my horror the bubbling had spread about 3 inches and looked terrible. I went so far as to try and scrape off the poly and it was taking everything off, down to the wood grain. I'm back at square one! But that doesn't bother me as much as not knowing what the hell I did to cause that!? Was it the moisture from the damp wipe down? I thought it was pretty dry from that, and why would it take EVERYTHING off? I need help!