My wife has a photographic print on what looks like resin-coated colour paper. A picture postcard has stuck to the photo, image side to image side, maybe during storage if the crate has got wet. The photo is about
30 years old.
I've soaked the print in cold tapwater and using my fingertip I've been able to rub off most of the card backing of the postcard, leaving a very thin layer of its printed image which is sticking extremely tenaciously to the photograph. I'm reluctant to scrape with a finger nail etc for fear of removing the resin-coated emulsion from the photograph. A large portion of the emulsion in an unimportant part of the photo has already detached.
What is the best way of trying to separate the postcard. There is always the ultimate fall-back of getting another copy of the picture (eg by scanning a print) since it's of her sister's wedding, about 30 years ago, so her sister has probably got a copy. If we're *really* lucky, there may even be a digital copy, since the reverse of the photo says "Jessops" and a filename of a JPG file, so the print was probably a print-it-yourself copy made from a digital photo that someone took.