Business: Gypsum & Deflation

A white, nonmetallic mineral is gypsum. It has been used as a building material throughout history. In raw form its principal use is as a retarder in cement, preventing it from setting too rapidly. It is also in wide industrial demand as a flux in smelting, as ''mineral white" or "terra alba'' in the paper, textile and paint trades. Blackboard chalk is raw, powdered gypsum molded with a binding substance. Pure gypsum is alabaster.

Most gypsum, however, is calcined by dehydrating with heat. With 75% of its moisture removed, gypsum becomes plaster of Paris.*...

Want the full story?

Subscribe Now

Subscribe
Subscribe

Get TIME the way you want it

  • One Week Digital Pass — $4.99
  • Monthly Pay-As-You-Go DIGITAL ACCESS$2.99
  • One Year ALL ACCESSJust $30!   Best Deal!
    Print Magazine + Digital Edition + Subscriber-only Content on TIME.com

Learn more about the benefits of being a TIME subscriber

If you are already a subscriber sign up — registration is free!