What is the gum made of that seals envelopes?
The glue applied to envelopes is of two basic types. The glue applied to the flap that is sealed by the consumer is usually a gum. A typical natural gum is gum arabic, derived from a substance produced by the acacia tree. Synthetic gums are often derived from dextrans, which are produced by the fermentation of sugar. The glue that holds the rest of the envelope must be stronger and more permanent. This glue is often derived from starches, which are obtained from corn, wheat, potatoes, rice, and other plants.
