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My old boss said never use PVA on leather covers, and I finally tested it on a scrap piece
Back when I worked at a shop in Denver, my boss kept saying PVA would crack any leather spine within a year and only used paste on them. I believed him for 6 years until last month when a customer brought in a 30 year old book he bound with straight PVA and the leather was still flexing fine. So I glued up three scrap leather spines, one PVA, one paste, one mix, and left them on the radiator for a couple weeks to see what happened. The pure PVA one did get stiff and a little shiny, but it never cracked, and now I'm wondering if his rule was ever really about cracking or just about how it looked. Has anyone here done a long term test like this, or is it one of those things we all just pass down?
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mark_chen621mo ago
The radiator test is smart but heat only speeds up one kind of aging. What nobody talks about with PVA on leather is what happens at the grain side over decades, because leather is acidic and PVA is not, so the glue holds but the leather under it slowly cooks itself. Paste is alkaline and buffered, so it sort of gets along with the leather long term. The Denver boss may have watched spines crack and blamed the PVA when the real problem was the leather drying out from the inside. Also a spine flexes way less than people picture, most of the stress is at the hinge, so a stiff PVA joint can survive fine if the book is opened gently. Your 30 year old customer book is one data point, but it lines up with the idea that we repeat rules about materials when we should be asking about the leather, the paring, and how the book actually gets used.
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