Gypsum plaster, types, uses, and advantages

Gypsum plaster, also known as plaster of Paris, is a type of plaster made from the mineral gypsum. It is a white or off-white powder that, when mixed with water, forms a paste that can be applied to walls and ceilings to create a smooth and even surface.

Composition of gypsum plaster

Gypsum plaster is a popular construction material that is made from the mineral gypsum. 

It is made from the mineral gypsum, which is a soft sulfate mineral composed of calcium sulfate dihydrate. This mineral is mined from various locations around the world and is typically found in sedimentary rock formations.

To make gypsum plaster, the mined gypsum is first crushed into a fine powder using a crusher. The powder is then further refined through a process called calcination. 

During calcination, the powdered gypsum is heated to a high temperature to remove any remaining moisture. The heat causes the gypsum to lose its water molecules, resulting in a dry, powdery substance called “plaster of Paris” or “calcined gypsum.”

Gypsum plaster formula

The chemical formula for gypsum plaster is CaSO4·2H2O, which represents the hydrated form of calcium sulfate.

The formula shows that gypsum plaster contains one calcium ion (Ca2+), one sulfate ion (SO42-), and two water molecules (H2O). 

When gypsum plaster is mixed with water, the water molecules are released, and the plaster hardens as the calcium sulfate dihydrate crystallizes.

The chemical reaction that occurs during the hardening of gypsum plaster can be represented as:

CaSO4·2H2O + 3H2O → CaSO4·2H2O·3H2O

This reaction releases heat and causes the plaster to harden and set into a solid form. The resulting material is strong, durable, and resistant to fire, making it a popular choice for use in construction and building applications.

Types of gypsum plaster

Anhydrite Gypsum Plaster

It is made by heating gypsum to 170°C. This process removes the water content from the gypsum, resulting in a fine powder known as Anhydrite Gypsum. 

This powder can then be used to create plaster, which is commonly used in construction.

Hemihydrate Gypsum Plaster

It is formed when hydrated gypsum is heated to a temperature of more than 170°C. This process results in a partially dehydrated form of gypsum known as Hemihydrite Gypsum. 

Plaster made from Hemihydrate Gypsum is also commonly used in construction and has similar properties to Anhydrite Gypsum Plaster.

Application of gypsum plaster

It is mixed with water to create a paste that can be applied to walls and ceilings using a trowel or a plastering machine. 

The paste is then smoothed and leveled to create a flat and even surface. Once applied, the plaster dries and hardens to form a strong and durable surface.

Properties of gypsum plaster

1. It is an excellent insulator, which means it helps to regulate temperature and can reduce energy consumption.
2. It is also a good sound insulator, making it ideal for use in areas where noise control is important.
3. It is a lightweight material, which makes it easy to handle and install.
4. It is a durable material that can withstand wear and tear, making it ideal for use in high-traffic areas.
5. It is resistant to moisture, which makes it ideal for use in areas with high humidity levels.
6. It sets to a smooth finish, making it easy to paint or decorate.
7. It is highly resistant to bacterial growth, making it a hygienic option for use in buildings.
8. It dries quickly, allowing the finishing coat to be applied on the same day as the undercoat.

Advantages of gypsum plaster

1. It is easy to apply, as it can be mixed with water to create a smooth and consistent paste that can be applied to a variety of surfaces.
2. It can be used on a wide range of surfaces, including concrete, brick, and plasterboard.
3. It is naturally fire-resistant and can help to prevent the spread of flames in the event of a fire.
4. It has good acoustic properties and can be used to improve the sound insulation of a building.
5. It can provide a smooth and consistent finish, which can be painted or decorated to match the desired style of a room.
6. It is a natural material that can be recycled or disposed of safely, which can make it a more environmentally friendly option than synthetic materials.
7. It is easy to work with and can be molded or shaped to create a variety of decorative effects.
8. It has low thermal conductivity, which can help to improve the energy efficiency of a building by reducing heat loss.

Disadvantages of gypsum plaster

1. It is not suitable for use in damp or wet conditions or for outdoor applications, as it can dissolve in water.
2. It has a limited shelf life and can deteriorate over time, particularly if it is exposed to moisture or humidity.
3. It must be stored in a dry and cool location, as exposure to moisture or high temperatures can cause it to deteriorate.
4. It is not suitable for use in humid climates, as it can absorb moisture and become soft or crumbly.
5. It is more expensive than other wall finishes, which can increase project costs.

Uses of gypsum plaster

1. Wall and ceiling finish: It is commonly used as a wall and ceiling finishing material in construction projects. It provides a smooth and even surface that can be painted or wallpapered.

2. Decorative features: It can be molded into a variety of decorative features, such as cornices, ceiling roses, and other intricate designs.

3. Molds for casting: It is often used to create molds for casting objects, such as statues, ornaments, and other decorative items.

4. Artistic applications: It is a popular material in the world of art, where it is used for sculptures, reliefs, and other artistic creations.

5. Dental applications: It is used in dentistry for making dental models and impressions.

6. Fire-resistant material: It is naturally fire-resistant, making it a popular material for use in fire-rated walls, ceilings, and other applications.

7. Soundproofing: It is a good sound-absorbing material, making it a popular choice for use in soundproofing applications.

8. Industrial applications: It is used in various industrial applications, such as in the manufacture of cement, wallboard, and plasterboard.

9. Medical applications: It is used in medical applications, such as for immobilizing broken bones and for making orthopedic casts.

Also read: Gypsum board, types, uses, advantages and disadvantages