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What is Gypsum Plaster?

Mike Howells
Mike Howells

Also known as Plaster-of-Paris, gypsum plaster is a building material that features similar properties to mortar or cement. It is created by heating gypsum, a soft, naturally-occurring mineral, to roughly 300 degrees Fahrenheit (150 °C), and then mixing it with water. The resulting paste hardens as it cools, forming a relatively soft, pliable finished product. Unlike mortar or cement, which dry much harder, gypsum plaster can be sanded or otherwise manipulated once cured, making it a good option for aesthetic, non-load bearing purposes.

Gypsum plaster derives its other name, Plaster-of-Paris, from the discovery of a large cache of gypsum in Paris, and its resulting proliferation as a building material in the city throughout the 1700s. Though its use can be traced back much farther — with samples dating from as far back as 7,000 BC in Mesopotamia — it gained widespread popularity throughout Europe after the Great Fire of London in 1666. During that fire, the city was nearly completely destroyed because flames spread through the close-packed arrangement of wooden buildings. Its utility as a fireproof material remains strong today.

Powdered gypsum is typically used to make plaster.
Powdered gypsum is typically used to make plaster.

Gypsum plaster is renowned for its use as an art medium, specifically for frescoes. Much of the reason that many Renaissance-period Italian frescoes remain intact and vibrant is due to the permeability of the plaster. This allowed inks to sink beyond the surface, much like the ink in a tattoo. This type of plaster is also a popular material in making casts for stone or metal sculptures, as it can be finely worked. Plaster can be used as a sculpture material itself when dried over a metal frame, though it is not particularly durable in this form.

A person wearing an orthopedic cast made with gypsum plaster.
A person wearing an orthopedic cast made with gypsum plaster.

In modern use, gypsum plaster is common in a number of industries. Orthopedic casts that incorporate plaster-soaked pieces of cloth remain a vital tool in the medical field to support and protect broken bones. In dentistry as well, plaster is used to create models of oral features for dental work. Gypsum plaster is still featured in architecture, particularly aesthetic pieces, and is used extensively in specialty industries, including film and theatre, where it can simulate materials such as bark or stone.

While a common and ancient material, gypsum plaster is not totally inert and can pose a health risk if used incorrectly. Improper use can result in severe burns, as the reaction between plaster and water releases potentially dangerous amounts of heat. Additionally, some types of plaster, particularly in older settings, can include particles of asbestos, a known carcinogen.

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Discussion Comments


Plaster-of-Paris is an appropriate name for gypsum. I think that one of the main sites for gypsum in Paris was the Monmartre section up on a hillside above Paris.

When I visited Paris, I went up the steep streets and stairs to Monmartre. The highlight is a beautiful church made from gypsum. I believe it took about 40 years to build. It's called Sacred Heart Church. It is just beautiful and shines brilliant white in the sunshine or under the lights at night.

Many artist frequented this area and I'm sure many of them used gypsum for their art.


Gypsum sure has a variety of uses. One that I remember my dad using is for wallboard. That's interesting that after the big fire in London, they started to use gypsum because it is fireproof. Those wooden buildings in London were stacked right on each other, and burned in a flash.

All the uses for gypsum in art is amazing. It is used in frescoes and sculptures. And then all the uses in the medical and dental fields.

I had no idea that there is a reaction between gypsum and water that can cause serious burns. We have to watch out for the type of gypsum that has asbestos in it, this can cause cancer.

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    • Powdered gypsum is typically used to make plaster.
      By: Kondor83
      Powdered gypsum is typically used to make plaster.
    • A person wearing an orthopedic cast made with gypsum plaster.
      A person wearing an orthopedic cast made with gypsum plaster.