Casein Glue Ingredients

Milk can be used to make a strong, long-lasting glue.

Casein -- milk's principle protein -- has been used to make glue since antiquity. Casein glues consist of casein and water, along with other ingredients such as borax ammonia or slaked lime. Casein is produced as a byproduct of the dairy industry and can be obtained in powder form. Alternatively, casein can be precipitated out of skimmed milk using heat and an acid such as vinegar.

Casein Glues in History

Casein has been used since antiquity to make a strong glue for wood and other materials. The ingredients used varied depending on time and place. The ancient Egyptians used glues made from casein mixed with powdered slaked lime (calcium hydroxide); this glue was mixed with colored pigments to make paints. One 15th century glue recipe calls for casein in the form of dried cheese.

Precipitating Casein for Glue

Precipitation -- the process of obtaining casein from milk -- is easily achieved in a domestic kitchen. A quantity of skimmed milk is heated in a saucepan, then a few spoonfuls of vinegar, lemon juice or other weak acid are added to the pan while the mixture is stirred. This separates the milk into solid curds and liquid whey. The curds, mostly made up of casein, are filtered to remove the whey. Any remaining acid can be neutralized with an alkali, such as a solution of baking powder. The casein can now be used as a glue on its own or dried for use as an ingredient in more sophisticated glues.

Powdered Casein Glues

Powdered casein needs to by hydrated before it can be used to make glue. It should be mixed with the amount of water called for in the recipe and then left for at least 12 hours, preferably overnight. If the casein is not properly hydrated, the glue will not be as successful. Once the casein is ready, it needs to be hydrolyzed -- broken down into its constituent amino acids. This is achieved using various alkalis.

Casein and Ammonia Glue

This glue requires powdered casein and ammonia salts in a ratio of 4:1. The casein powder is mixed into a smooth paste with a small amount of water, then warm water is added to make a liquid mixture. The ammonia salts are mixed in a similar way, then the two solutions are combined. Lots of gas is produced, causing the mixture to froth. Once the foaming stops, the glue is ready for use.

Casein and Borax Glue

Casein-borax glue can be made using powdered casein and borax in a 5:2 ratio (for instance, if 40 grams of casein were used, 16 grams of borax would be required). The casein is hydrated over a period of 12 hours. The borax needs to be dissolved in hot water. The two can then be mixed together to make glue.

Lime-Casein Glue

Slaked lime is the name commonly used for calcium hydroxide, a strongly alkaline substance. A lime-casein glue can be made using hydrated powdered casein or using fresh casein in curd form produced using the precipitation method outlined above. The slaked lime is mixed with the casein to produce a smooth paste. This paste is a powerful glue.

References

• Roger-Hargrave.de: The Case for Casein; Roger Hargrave
• Oil Painting Art: Glues and Sizes; 2008
• Education.com: The Holding Power of Homemade Casein Glue versus Commercial Glues p1; Mike Calhoun
• Education.com: The Holding Power of Homemade Casein Glue versus Commercial Glues p2; Mike Calhoun
• Kremer Pigmente: Recipes: 63200 Casein; Dr. Georg Kremer,

Resources

• Sinopia Pigments and Materials: Casein & Milk Paint Recipe