What is the glue on the back of postage stamps and envelopes made from? | Notes and Queries

What is the glue on the back of postage stamps and envelopes made from?

• THE GUM on British stamps is composed of polyvinyl alcohol and dextrin. The dextrin is derived from starch (e.g. potato) and the vinyl alcohol is a synthetic derived from petroleum. The gum used on ready-stamped stationery items is a blend of polyvinyl acetate and dextrin with the exception of aerogrammes, where the gum is a blend of polyvinyl acetate and polyvinyl alcohol. Slimmers may be interested to know that a single standard postage stamp contains 5.9 calories and Special or Commemorative stamps 14.5 calories. To avoid offending any religious groups or vegetarians, no animal products are involved.

  Jane Ormrod, Philatelic Marketing Manager, Royal Mail, London EC1.