It was somewhere outside Barstow when Mike Halmarack
wrote:

http://www.tki.org.nz/r/science/scie.../milk_glue.htm

Years ago (family dairy farm) I experimented with making this stuff
commercially - or rather milk paint, which is very similar. To make
anything more than a panful, or to have any repeatable product
quality, it needed a spray drier.

Mary will of course be boiling up stag's horns or making viking cheese
glue instead.