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Update: the 30 year binder who said skip the wheat paste on my first coptic got it wrong
Back in April I was binding a 200 page sketchbook for a friend's birthday and an old timer at the shop in Asheville said wheat paste was overkill for coptic and PVA would hold just fine. I listened to him because he has been at it since 1988 and I figured he knew better. Six weeks later the spine cracked open right at the third signature and my friend sent me a photo of pages falling out. I redid the whole thing with a 50/50 wheat paste and PVA mix and it has been solid for 5 months now, even with him shoving it in a backpack. Has anyone else had PVA alone fail on coptic, or did I just get a bad batch?
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miller.eva1d ago
The 1988 thing is the part that gets me. Time on the job does not always mean the advice is right for every case. Coptic is an open spine, so the whole point is flex. PVA dries hard and stiff. Once it cures it wants to snap, not bend, and a 200 page block is heavy enough to do the snapping.
Your 50/50 mix is basically the old school answer for that reason. The paste keeps it flexible and gives you open time. The PVA adds the grab. So yeah, it was not a bad batch. It was the wrong glue for that structure.
One small thing though. Calling it a spine crack at the third signature is a bit off. In a coptic there is no real spine, just the sewing and the exposed back. What cracked was probably the glue line between signatures near that spot. Same fix, just different words.
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