What transparent glue can be used to hold a piece of plastic to a picture of the same size (which is on paper, I think)? So transparent that it won't distort the image of the picture, and won't even be noticeable when looking at the picture?
My friend has a lady's compact, for face powder, that is about 80 years old, with a picture of -- I forget -- either Queen Elizabeth or the SS Queen Mary in it. The picture was covered with a transparent piece of plastic (or celuloid?) which recently came off, risking the safety of the picture.
He assumed that there were tabs in the plastic that fit slots somewhere in the compact to hold the plastic in place, but there aren't.
Now he figures there was a transparent glue between the plastic and the picture which finally gave way. Even though he sees no trace of the glue (it's transparent after all.)
What glue can he use that is transparent that will hold this light piece of plastic to the picture (which is on paper, I think)?