Written by: Bexx Caswell-Olson
Primary Source: Wallace Conservation Lab, October 6, 2015
Vellum is a hygroscopic material, which means that it has the ability to attract and hold water molecules from the surrounding environment.
Vellum will expand in humid conditions, and contract in dry conditions. Even normal fluctuations in temperature a humidity can cause vellum bindings to warp. Over time, this book became badly warped. At it’s thickest, it was a whopping 70 mm (2.75 in) thick.
I gently humidified the front and back covers to help them relax – you need be careful when exposing vellum to water – too much, and it can turn back into rawhide!
Once the covers had relaxed, I put the book under weight to flatten it out. I left it that way for about a week – plenty of time to dry and become accustomed to being flat. After treatment, the book was a mere 46 mm (1.8 in) thick – that’s a reduction of 24 mm (.94 in)!
To help keep the book flat, it has been housed in a custom made box that keeps it under light pressure.
Find this book in our Special Collections here.