Pro tip: I glued a spine with the press clamped too tight at my bench in Toledo and cracked the hinge on a 1930s atlas
I backed the clamp off a quarter turn, re-pasted the mull with wheat starch, and let it dry under light weight for 12 hours, which saved the joint but left a hairline scar on the board. Has anyone gotten a hide glue reback to stay invisible on older cloth spines?
I heard on a bookbinding podcast that tinting the hide glue with a touch of acrylic before it sets helps it blend into old cloth. Might be worth a test on scrap first though.