|MadSci Network: Chemistry|
Traditional glues are often made from materials very similar to those we eat. Glues need to have a property of stickiness and tackiness -- protein molecules, among others, often have these properties. For example, gelatin, which is obtained from collagen (a major component of many biological tissues, including muscle, bone, and hides) is a protein that we use in food and to make glue. Milk protein is the source for "Elmer's" glue - a popular white glue in the U.S. Egg proteins are known for their stickiness which is why we often dip foods to be coated in egg or egg white. As the protein dries it forms a film that can adhere to materials by various types of bonds. That is what a glue is. So it is not surprising that these same materials will stick to the plate or pan when they dry. The practical consequences is that you should not leave the dishes "overnight" but clean them immediately after the meal. (This is also a good sanitary practice.)
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