Ingredients

• The foundation of plaster of Paris is heat-treated gypsum powder. Chemically, gypsum powder is calcium sulfate dihydrate. To use, it is mixed 2 parts plaster to 1 part water.
  
  

Function

• Plaster of Paris is also known by the name gesso. Gesso is used to create the foundation for many art forms including sculptures, paintings and gilded frames.
  
  

Characteristics

• The size and volume of plaster of Paris does not change as it dries, because the gypsum powder dries before the water evaporates. This gives the plaster a smooth finish.
  
  

Name Origin

• While plaster of Paris use predates the founding of the city of Paris, this gypsum compound is commonly referred to today as plaster of Paris. This is because gypsum is found in abundance on Montmartre hill in Paris.
  
  

Considerations

• The drying time of plaster can be affected by letting the mixture rest for 10 minutes before it is mixed. This will slow down the process, while mixing the gypsum powder with hot water will speed up the drying time.