I too use release paper and acid free interleaving paper between the platen. I also turn the sandwich 180 around when 3/4's time has expired. I tack only on three corners. Cool under a metal plate and have not run into your situation. The prints are on FB paper and the mat board is 100% rag. However, I have been shying away from dry mounting and going to archival corners more frequently because if the board is damaged or develops climate stains with our high humidity the print is shot.

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