Plaster of Paris

Plaster of Paris is the building material that consists of calcium sulfate hemihydrates, which is fine, white colored powder. Plaster includes; plaster of Paris, lime plaster and cement plaster. Since ancient times it is getting used. Egyptians, Greeks, and Romans used it for sculpting their tombs and building for fire proofing.

How it is obtained?

Plaster of Paris is obtained by heating gypsum or calcium sulfate about 140 to 180 degree C. If gypsum is heated in certain temperature, it tends to lose two third of its water content hence leading to the formation of plaster of Paris. The name is derived from the gypsum deposits in the Montmartre hill in Paris. It is more similar to building materials like mortar and cement. By mixing with water, a paste can be made and while mixing with water, it liberates heat and hardens. While plaster of Paris is mixed with water, the hydrogen bonding is formed between calcium and sulfate ions, that’s why plaster is soft and smooth. While using for specific purpose, the plaster of Paris can be molded in to desired shape before it gets harden. Even after drying, to certain extent plaster of Paris will remain soft and with the use of sandpaper or metal plaster of Paris can be easily manipulated.

Uses

Plaster of Paris is widely used in home decors, various design can be made in the walls and ceilings. It is used in arts and architecture also. Plaster of Paris is widely used in orthopedics to make smooth casts for broken limbs.  Due to its speed setting, it is consider mainly as favorite sculpting material for many modern sculptors. In forensic science, molds of foot prints are made by using plaster of Paris for investigation purpose.

Methods for preparation

Plaster of Paris can be prepared in many methods. The easiest one is by creating the plaster of Paris either with white glue or white flour. In the white glue method, prepare a paste of white glue and warm water. Make sure that you are gently adding the warm water by continuously stirring. Stop adding warm water as it get into the form of paste, thus plaster of Paris is ready.  In the white flour method, prepare the plaster of Paris by mixing white flour and water. From the homemade plaster of Paris, one can make masks and bubble paint.

Questions:

• What is called plaster of Paris?
• Is plaster of Paris getting used in architecture?