Plaster of Paris | Uses, Types, Formula, Importance,

Plaster of Paris and its Uses

Through this content, we aim to provide the information and details of the Plaster of Paris and its uses.

After going through this content, you will know the meaning and component of POP better. Also, know the types and importance of POP.

Also, identify the characteristics of POP such as waterproof, danger intensity, eco-friendly, and more.

The content talks about the derivation of the name ‘Plaster of Paris’ as well.

We have also included the formula of POP, alternatives, advantages, and disadvantages, and how it is prepared.

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What is Plaster of Paris?

Made up of gypsum, the Plaster of Paris is a white colour powder. It is a popularly used substance for sculpting, casting, and gauze bandages.

Chemically, it is calcium sulphate hemihydrates which are obtained from heating gypsum.

We have listed down the properties of Plaster of Paris which are as follows:-

  • It is a white colour powder
  • When water is mixed with it, the gypsum crystals are produced which leads to set into a hard mass
  • It has an exothermic setting process and maybe catalyzed by sodium chloride. It can be retarded by alum or borax.
  • At 473K, Plaster of Paris forms anhydrous calcium sulphate known as dead burnt Plaster of Paris.

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What is Plaster of Paris made of?

It is made up of heated gypsum at a high temperature. The process of preparing it described later in the content below.

Is Plaster of Paris waterproof?

No, It is not a waterproof substance. It is made waterproof by mixing other materials to be used in interiors and exterior.

It is an extensively dry and porous substance. Whenever exposed to water, it will absorb it.

Often to make it waterproof, a coating of heavy-duty primer is applied and then painted with heavy-duty extension paint or any other paint.

For those who do not wish to paint, applying a coat of linseed oil is effective. Lightly sanding the plaster surface before applying linseed oil allows better absorption.

Various other waterproofing methods and techniques are used based on the need and applicability.

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Is Plaster of Paris dangerous?

Yes, if not properly handled, it can be harmful and dangerous. It is a calcium sulfate hemihydrates with silica and asbestos and impurities.

Upon inhalation, it can lead to permanent lung damage and other ailments.

The mixing of Plaster of Paris and water is an exothermic reaction which may lead to severe consequences if not taken care of.

However, it is often used by children in arts, crafts, decoration, and other proposes.

If carefully used, it can be fun to use. Certain safety precautions should be followed such as:-

  • Wear a mask to prevent inhaling the powder
  • Wear gloves while working with it to avoid skin contact
  • Do not wash Plaster of Paris down the drain as it can set up the pipes and drain clogging it.
  • Do not pour put your hands inside the hardening mixture

What are the types of Plaster of Paris?

There are three types of plaster which are prevalent in use which are as follows:-

Gypsum Plaster

This is produced by heating gypsum to a temperature of 300 degrees Fahrenheit. Also, if heated above 392 degrees Fahrenheit, it turns into anhydrite.

When you mix water with the gypsum plaster powder or anhydrite, it turns into gypsum.

Lime Plaster

The mixture of sand, calcium hydroxide and other inert fillers are Lime Plaster.

Limestone is heated to make quick lime and then slaked lime is produced by adding water to it. It is often called white powder or wet putty.

Cement Plaster

The mixture of suitable plaster, Portland cement, sand and water is called cement plaster.

It is applied to the exteriors and interiors to obtain a smooth surface. A final layer of gypsum plaster is often added over the cement plaster.

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What are the uses of Plaster of Paris?

It has plenty of uses and applications across several sectors. From buildings, decoration to arts, medical and dentistry, Plaster of Paris is used.

We have listed down a few of the uses of Plaster of Paris which are as follows:-

Building material

Plaster of Paris is used as a building material by constructors and architects.

It is often used as a protective coating on the walls and ceiling before painting is done. Alongside this, it offers a smooth surface and aids in fire-proofing as well.

Moulding and casting agent

It is an excellent moulding and casting agent for various purposes.

Several statues, showpieces, and other decoration elements are made by using it.

Medical applications and purposes

In hospitals and medical departments, it is often used in fracture cases. Orthopaedics uses it to put casts around bone fractures.

This offers support and stiffness to the bone and aid in the process of healing.


In radiotherapy, it is used to manufacture individualized immobilization shells for the patients.

Plaster bandages are used to develop the patient’s head and neck impression.

The paste of the plaster is then used to fill the impression and make a plaster dummy.

Decoration element

Plaster of Paris is used to make decorative pieces and materials. It is used in making statutes, showpieces and more.

Also, it can be used on walls creatively to make new designs and pattern as a decorative element.

It can also be used for making false ceilings, beautification, and before painting the walls.

Art and crafts

For various arts and craft purposes, children and adults use Plaster of Paris. Also, it is used by artists and painters to create beautiful patterns or designs.

The use of Plaster in arts and craft depends on the need and applicability.

In dentistry

Dental clinics or dentists use Plaster of Paris to make moulds or casts of the teeth. They are often used for temporary purposes.

It is used to make replicas of teeth and tissues. Also, it is used to make wax false teeth.

For fireproofing

Plaster of Paris being fire-resistant is used in buildings, fireproofing products, and fire protection systems.

It prevents the spread of fire as the plaster coating discharges water vapour in case of fire.

Alongside this, it protects by slowing down the heat transfer into steel or concrete elements preventing the breakdown.

3D printing

Nowadays, gypsum plaster is significantly being used in 3D printing. In this, water is specifically applied by the inkjet head.

Burial services

Several funeral houses use Plaster of Paris to rejoin the cut-off parts of dead bodies, remake the damaged tissues or to fill the wounds occurred.

What is the importance of Plaster of Paris?

It is important owing to its uses and applications in several ways and sectors. From schools, building material to medical departments, it is used.

Why is it called Plaster of Paris?

It has been known to people and used since ancient times. It was first made around 9000 years ago and was used by ancient Greek, Egyptian and Roman civilizations.

However, a large scale use was noticed when it was required to be used in all constructions taking place in Paris.

As a result of a fire in London in 1666, the king of France ordered all the wooden walls to be covered with plaster immediately to prevent such fires.

As a result, a large-scale gypsum mining was carried around Paris and gypsum was available in huge quantities.

Paris became the center of plaster production in the 18th century, thus, the name Plaster of Paris.

What is Plaster of Paris formula?

Plaster of Paris is also known or called gypsum plaster. The chemical formula of it is denoted as CaSO4.H2O or 2CaSO4.H2O

How is Plaster of Paris prepared?

Manufacturing of Plaster of Paris takes place by heating gypsum in rotary kilns at a temperature of 300 degrees Fahrenheit. It is partially dehydrated.

The chemical reaction which takes places is as follows:-

2 (CaSO4.2H2O) ——– 300 ° F   ——–      2(CaSO4).H2O + 2H2O

When you heat gypsum at 300 degrees Fahrenheit, it loses the water molecules and turns into calcium sulfate hemihydrates.

At this point, it is called the Plaster of Paris. When you mix water with dry Plaster of Paris, it turns back into gypsum.

The hardening process of the plaster starts around 10 minutes after blending and takes about 45 minutes to complete.

The mixture is completely set in 70 to 75 hours.

What is an alternative to Plaster of Paris?

Materials such as softwood, limestone, granite, sandstone, moulding and casting clay, wax and other such substances can be excellent alternatives.

Is Plaster of Paris eco-friendly?

No, the Plaster of Paris is not an eco-friendly material as it takes a long time to decompose and harms the environment.

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