Re: How does glue made with milk work?

Originally, glue was made from other animal parts like the hoofs of cattle 
and horses.  You may have heard that old horses are sent to the glue 
factory.  Although, this seems cruel, it actually is like recycling the 
chemicals found in the animals bodies after they die.  It is the protein in 
the animals, as well as, the milk that work to make very strong bonds that 
results in the stickiness of milk when combined with the acid of vinegar.  
The baking soda results in another reaction which as you have experienced, 
results in a very good glue.  The real answer to your question is that, the 
proteins in the milk make the structural foundation for the glue.  The 
reason that skimmed milk works best is that the fat only interferes with 
the bonds necessary for a strong glue.