Undenk has a great post with two classic wheatpaste recipes. At least we think there are two, b/c the one from 1880s (photo reposted) is difficult to read.
Here’s our tried and tested wheatpaste recipe:
Makes two litres of Wheatpaste
8 cups of water, or around 2 litres
1.3 cups of Flour
90 grams of Sugar
Firstly, dump your flour in a bowl, and slowly pour in cold water whilst mixing. The aim is for a cold slurry that is easy to pour.
Boil the 8 cups in a big old saucepan and then slowly pour in the slurry.
Allow to cool.
Decant into Bike drink bottles or similar to squirt onto your poster / brush and prevent spillage.
Tip it out after a week. The shit stinks.