For jacketing molds and for use wherever a soft, non-detailed inexpensive plaster is needed. Available from Douglas & Sturgess, Inc., for $4.25 for a 10 lb bag or $23.50 for a 100 lb bag.

An early form of commercial stone. Hydrostone is a kind of concrete block from which many post-Explosion houses were built. Regular concrete was prone to water damage: hydrostone was made in a patented process designed to reduce the amount of water that could get into the stone.