I learned a long time ago, there are small little bugs, even in the most spotless house that like to get into picture frames. I was again told to get those little packets of bug stuff to tape to the pack of the picture. They last for a few years. I have not had a bit of trouble since then. You seal the back with brown paper, and you can't get the packet where you want it. Also if the picture slips in the matting, you have to tear the paper off. Some of the purchased art work I have, this has happened to. IT IS a PIA to take off and replace.