If you didn't use mounting tissue you might consider soaking it in water for a while and gently wipe with cotton while it is under water. I've never run into this nor have I done what you do. A friend gave me some prints of his grandfather that were stuck to glass from a frame. I first scanned them because no negative was available and then soaked with some photoflo in water. They finally separated. I rewashed them and let them air dry as I do with all my prints. Since it sounds like you can reprint, you have the luxury of messing up.

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