Casein glue is glue made from the protein in milk. It is a very simple and quick glue to make and because it comes from milk it is non-toxic, safe and fun for kids in projects and woodworking.
Skim Milk - http://amzn.to/2G7OYpC
Vinegar - http://amzn.to/2FNHngs
Baking soda - http://amzn.to/2G9JCu9
Step 1: Separate the Casein From the Whey
To begin, start by warming up two cups of milk in a saucepan. The milk should be brought to a temperature that is warm to the touch, but not hot enough to hurt your hand. Next, add 2 ½ to 3 tablespoons of vinegar and stir the mix. Look for the whey to turn almost clear and separate into large chunks of casein and liquid whey. This separation will happen very quickly. If you have been stirring for a while and this does not happened then just add a little more vinegar.
Step 2: Strain and Deacidify
After the whey and casein have separated, you can strain them through a towel or cheesecloth. Another way is to clump together the casein in the mix and just pull it out of the saucepan and dump off the whey. Next, we need to add 1 tablespoon of baking soda. This will react with the vinegar to make the pH less acidic.
Step 3: Add Water and Storage
In this step, add 3 to 4 tablespoons of water and warm it on the stove. The baking soda will create bubbles and you need to watch the pot carefully so it doesn't suds up. Continuing mixing the lump of casein until it becomes completely liquid in the water. At this point it is done and ready for use. You can use it straight out of the saucepan or store it in a jar for later use. If kept in the fridge it should last for several weeks, but if kept on the shelf you might want to use it that day as it will start to smell if it sits around too long.
Step 4: Use
Casein glue can be used for crafts or anywhere where paper craft glue would be usually used. Some use it for woodworking or other larger crafts. Since it is made from milk, it is completely safe to use in food-related crafts and other places where kids might be tempted to drink the glue.