I'm going to give you some free advice, because I learned the hard way. I had a painting that was complete but it developed a bubble at the framers. I haven't had this problem before and I don't know why it happened this time. I stretch my paper and staple it in preparation for painting, so before I remove it from the board it is dry and flat. Naturally I was never going to be satisfied with it bubbled, so I decided to bring it home and flatten it. No problem. I put distilled water on the back and let it sink in then layered weights on the back and left it to dry. Easy. (Smaller pieces or paintings on 300 lb. paper I don't usually staple.) I have several boards that I dry my work on and I know which ones they are because I put yellow electric tape around the edges. Why? The boards I paint on have left-over paint on them and I'm concerned the extra paint might transfer. On the drying boards - no problem. Well this time I didn't have any drying boards available. What I did have available was some leftover acrylic sheets I had used in a workshop. How many problems did this cause? Let me count the ways. First, it wouldn't dry. Well, that makes sense of course looking back on it - after all, it's acrylic so no air will move through it. So I left it to dry longer. Uh oh. What happened? When I went to remove it - it stuck. When I finally got it removed, about half the painting was left on the acrylic sheet. And that wasn't all! It also pulled tiny little shard-like pieces of paper up. It took a second for my head to get around all the problems I was facing. I just stood there, gobsmacked. After the initial shock wore off I cursed a blue streak and pulled my hair. Aaargh!!!! So what did I do? I fixed it - as in fully restored. It took 50 hours of concentrated effort, but I did it. Luckily I had a photo of the finished painting so I could use it as a go-by. And the truth is that it was easier because I just did what I had already done. I had already made all the decisions the first time around. I began to think restoration work wasn't too bad. But the time, tick-tock, I won't get that back. Hard lesson learned. Save yourselves! Don't. Ever. Do. This. Back to my brushes.
"Disappointment is an endless wellspring of comedy inspiration." - Martin Freeman