Saw this today and thought it might be handy for something sometime in the future, so I’m making a note. It came from a farm know-how page

Mix equal parts of gem salt, rock alum, white vinegar, chalk and Peebles’ powder. After the mixture becomes quiet, put into it any wood or porous substance, and the latter becomes like stone.

Google tells me Peebles’ Powder is powdered skim milk.