Found out the hard way that wheat paste pH matters for old bindings

I was restoring a 1920s novel for a client last month and used my usual wheat paste. The pages started yellowing around the repairs after a week. Turns out my paste was testing at pH 9.2, way too alkaline for paper from that era. I read a 2019 article from the American Institute for Conservation that says paste should be between pH 6.8 and 7.2 for anything pre-1950. Anyone else actually test their paste pH regularly?

2 comments

2 Comments

faithbarnes13d ago

Have you tried making your own paste from scratch? I switched to cooking my own wheat starch paste a couple years back and it made a huge difference. I test it with pH strips every batch now, usually lands around 7.0 if I use distilled water and let it cool right. For that 1920s stuff, I'd also add a tiny bit of calcium carbonate buffer just for safety.

lucas6313d ago

Oh man, that paste route. I tried cooking my own wheat starch paste for a while too. Had the same good results until one batch went bad on me. Realized I wasn't letting it cool long enough after cooking. The pH strips are a lifesaver though. For older paper like that 1920s stuff, I'd mix in a tiny pinch of calcium carbonate too, like you said. Keeps things stable without making a mess.