Calcium Sulfate, Hemihydrate

2.5 (NIOSH, 2024) - Denser than water; will sink

Density (for the alpha hemihydrate): 2.76 g/cm³

2.5

2.5

0.3 % at 77 °F (NIOSH, 2024)

Solubility in water, g/100ml at 25 °C: 0.30

(77 °F): 0.3%

325 °F (Loses H2O) (NIOSH, 2024)

163 °C

325 °F (loses H₂O)

325 °F (Loses H2O)

0 mmHg (approx) (NIOSH, 2024)

0 mmHg (approx)

0 mmHg (approx)

Plaster of paris appears as white or yellowish, finely divided, odorless powder consisting mostly or entirely of calcium sulfate hemihydrate, CaSO4*1/2H2O. Forms a paste when it is mixed with water that soon hardens into a solid. Used in making casts, molds, and sculpture. Generally non-toxic.

Large Crystals

Dry Powder

White or yellowish, finely divided, odorless powder; [NIOSH]

FINE HYGROSCOPIC WHITE POWDER.

White or yellowish, finely divided, odorless powder.

This chemical does not meet GHS hazard criteria for 100% (75 of 75) of all reports.

Not Classified

Aggregated GHS information provided per 75 reports by companies from 2 notifications to the ECHA C&L Inventory.

This chemical does not meet GHS hazard criteria for 100% (39 of 39) of all reports.

Not Classified

Aggregated GHS information provided per 39 reports by companies from 2 notifications to the ECHA C&L Inventory.

Chemical: Sulfuric acid, calcium salt (1:1), hemihydrate

Sulfuric acid, calcium salt, hydrate (2:2:1) is listed on the EPA's Chemical Data Reporting (CDR) system. Manufacturers and importers of Sulfuric acid, calcium salt, hydrate (2:2:1) are required to report information about their production and use of this chemical to the EPA under the Toxic Substances Control Act (TSCA). (40 eCFR Part 711)

Plaster of Paris (Ca(SO4).1/2H2O) is listed on the EPA's Chemical Data Reporting (CDR) system. Manufacturers and importers of Plaster of Paris (Ca(SO4).1/2H2O) are required to report information about their production and use of this chemical to the EPA under the Toxic Substances Control Act (TSCA). (40 eCFR Part 711)

Calcium sulfate hemihydrate: Does not have an individual approval but may be used under an appropriate group standard

Plaster of Paris (Ca(SO4).1/2H2O): Does not have an individual approval but may be used as a component in a product covered by a group standard. It is not approved for use as a chemical in its own right.

PLASTER OF PARIS is non-flammable and non-combustible. Has generally low chemical reactivity but can act as an oxidizing agent under extreme conditions. Decomposes at high temperature to generate toxic oxides of sulfur. Reacts exothermically but slowly with moisture in the air or water to form gypsum CaSO4.2H2O.

Not Classified

Not Classified

Specific target organ toxicity - Single exposure - Category 3 (Respiratory tract irritation)

Fresh air, rest.

Rinse and then wash skin with water and soap.

First rinse with plenty of water for several minutes (remove contact lenses if easily possible), then refer for medical attention.

Rinse mouth.

Excerpt from NIOSH Pocket Guide for Plaster of Paris:

(General first aid procedures)

Cough.

Redness. Pain.

irritation eyes, skin, mucous membrane, respiratory system; cough

2023: 58,972,905 lb

2023: 34,600 lb

Other

Filler

Information on 15 consumer products that contain Calcium sulfate hemihydrate in the following categories is provided:

Information on 31 consumer products that contain Plaster of paris in the following categories is provided:

Primary Metal Manufacturing

Non-metallic Mineral Product Manufacturing (includes clay, glass, cement, concrete, lime, gypsum, and other non-metallic mineral product manufacturing)