Dennis, I have not used anything on the faces. On a could I have sprayed with a clear arylic that I used to try and hopefully keep the painted face from cracking. I have had a few that when I went ot bend them around the tube the paint just flaked off. But usually I don't use anything. I have not had any issues, but then again I was using Epoxy. I have three new blanks with the parts glued on now and letting them off gas for a couple days before I pour them, going to try Alumilite, out of epoxy. I'll let you know how they do.
Mike