Gypsum vs. Plaster — What's the Difference?

Raw material.

Building material.

Fire resistance.

Made from gypsum.

Natural mineral.

Hardens over time.

Versatile applications.

Artistic use.

Humidity regulation.

Finish and decoration.

Gypsum is a soft sulfate mineral composed of calcium sulfate dihydrate, with the chemical formula CaSO4·2H2O. It is widely mined and is used as a fertilizer and as the main constituent in many forms of plaster, blackboard/sidewalk chalk, and drywall. A massive fine-grained white or lightly tinted variety of gypsum, called alabaster, has been used for sculpture by many cultures including Ancient Egypt, Mesopotamia, Ancient Rome, the Byzantine Empire, and the Nottingham alabasters of Medieval England.

Plaster is a building material used for the protective or decorative coating of walls and ceilings and for moulding and casting decorative elements. In English, "plaster" usually means a material used for the interiors of buildings, while "render" commonly refers to external applications.

A widespread colorless, white, or yellowish mineral, CaSO4·2H2O, used in the manufacture of plaster of Paris, various plaster products, and fertilizers.

A mixture of lime or gypsum, sand, and water, sometimes with fiber added, that hardens to a smooth solid and is used for coating walls and ceilings.

A mineral consisting of hydrated calcium sulphate. When calcinated, it forms plaster of Paris.

Plaster of Paris.

A mineral consisting of the hydrous sulphate of lime (calcium). When calcined, it forms plaster of Paris. Selenite is a transparent, crystalline variety; alabaster, a fine, white, massive variety.

A pastelike mixture applied to a part of the body for healing or cosmetic purposes.

A common white or colorless mineral (hydrated calcium sulphate) used to make cements and plasters (especially plaster of Paris)

Chiefly British An adhesive bandage.

To cover, coat, or repair with plaster.

To cover or hide with or as if with a coat of plaster

To apply a plaster to

To cover conspicuously, as with things pasted on; overspread

To affix conspicuously, usually with a paste

To make smooth by applying a sticky substance

To make adhere to another surface

To inflict heavy damage or injury on.

To defeat decisively.

To apply plaster.

(uncountable) A paste applied to the skin for healing or cosmetic purposes.

A small adhesive bandage to cover a minor wound; a sticking plaster.

(uncountable) A mixture of lime or gypsum, sand, and water, sometimes with the addition of fibres, that hardens to a smooth solid and is used for coating walls and ceilings; render, stucco.

(countable) A cast made of plaster of Paris and gauze; a plaster cast.

(uncountable) plaster of Paris.

(transitive) To cover or coat something with plaster; to render.

(transitive) To apply a plaster to.

(transitive) To smear with some viscous or liquid substance.

(transitive) To hide or cover up, as if with plaster; to cover thickly.

To bombard heavily or overwhelmingly; to overwhelm with (weapons) fire.

To smooth over.

An external application of a consistency harder than ointment, prepared for use by spreading it on linen, leather, silk, or other material. It is adhesive at the ordinary temperature of the body, and is used, according to its composition, to produce a medicinal effect, to bind parts together, etc.; as, a porous plaster; sticking plaster.

A composition of lime, water, and sand, with or without hair as a bond, for coating walls, ceilings, and partitions of houses. See Mortar.

Calcined gypsum, or plaster of Paris, especially when ground, as used for making ornaments, figures, moldings, etc.; or calcined gypsum used as a fertilizer.

To cover with a plaster, as a wound or sore.

To overlay or cover with plaster, as the ceilings and walls of a house.

Fig.: To smooth over; to cover or conceal the defects of; to hide, as with a covering of plaster.

A mixture of lime or gypsum with sand and water; hardens into a smooth solid; used to cover walls and ceilings

Any of several gypsum cements; a white powder (a form of calcium sulphate) that forms a paste when mixed with water and hardens into a solid; used in making molds and sculptures and casts for broken limbs

A medical dressing consisting of a soft heated mass of meal or clay that is spread on a cloth and applied to the skin to treat inflamed areas or improve circulation etc.

A hardened surface of plaster (as on a wall or ceiling);

Adhesive tape used in dressing wounds

Cover conspicuously, as by pasting something on;

Affix conspicuously;

Apply a plaster cast to;

Apply a heavy coat to

Coat with plaster;

Dress by covering with a therapeutic substance

Yes, plaster can also be made from lime or cement, each with different properties and uses.

Gypsum is preferred for its ability to regulate indoor humidity and its fire-resistant properties, contributing to healthier and safer indoor environments.

Plaster is made by heating gypsum to remove part of its water content, forming plaster of Paris, which becomes a paste when mixed with water and hardens over time.

Plaster finishes provide a smooth, durable surface that can be decorative. They are also capable of regulating humidity when made from gypsum.

Once hardened, plaster of Paris cannot be re-melted, but it can be crushed and recycled in some applications.

Gypsum is used as a raw material to produce plaster, drywall, and other building materials, and as a soil conditioner in agriculture.

Gypsum-based plasters are lighter, easier to work with, and have better insulation properties, while cement-based plasters are more moisture-resistant and suitable for exterior use.

Gypsum is considered environmentally friendly due to its natural occurrence, recyclability, and use in improving soil condition, though mining and processing impacts should be managed.

Gypsum's fire resistance adds an extra layer of safety to buildings, slowing the spread of fire.

Its malleability when wet and durability when dry make plaster ideal for sculptures and decorative moldings.

Yes, plaster can be applied over existing surfaces, but preparation such as cleaning and sometimes applying a bonding agent is necessary.

Gypsum and plaster can absorb excess moisture from the air and release it when the air is dry, helping to maintain a balanced indoor humidity level.

Generally safe, gypsum and plaster can pose dust inhalation risks during mixing or sanding, so protective measures are recommended.

The drying time for plaster varies based on thickness, temperature, and humidity, typically taking a few days to fully set.

The environmental impact is managed through restoration projects, recycling of gypsum products, and by adhering to regulations that minimize environmental damage.