A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
Plaster of Paris
Table of contents
Key Data
Formula: CaSO4.½H2O
CAS: 26499-65-0
Other names: Calcium sulfate hemihydrate
Appearance: White or yellowish powder
Solubility in water: 3g/litre approx. Reacts exothermically with water to form gypsum (CaSO4.2H2O)
Thermal decomposition: At 163°C gives off water. Over 1200°C it forms calcium oxide and toxic sulfur trioxide
Dustiness:
Composition/Impurities
Impurities may include clay, limestone, and traces of quartz
Uses
Used for making moulds, plaster batts etc
Exposure Routes
Skin and Eye Exposure
May irritate the eyes or sensitive skin, and cause dry skin
Skin Absorption
No
Inhalation
May irritate the respiratory system
Ingestion
No harm in small quantities. In larger quantities it may need to be surgically removed from the stomach once set; drinking glycerine or large quantities of water may delay setting.
Toxicity
Not toxic
Fire Hazard
No
Health and Safety Practice
Not to be used for taking casts of the body, as the high heat is likely to burn the body parts held in the setting plaster.
Wear safety glasses, and remove contact lenses, before working with Plaster of Paris
Disposal
Prevent the powder or slurry getting into drains or watercourses
Regulatory Requirements
Dust Limits
| Regulator | 8hr TWA mg/m3 | 15 min TWA mg/m3 | Notes |
| UK HSE | 10 | Inhalable dust | |
| UK HSE | 4 | Respirable dust | |
| US NIOSH REL | 10 | Inhalable dust | |
| US NIOSH REL | 5 | Respirable dust | |
| US OSHA PEL | 15 | Inhalable dust | |
| US OSHA PEL | 5 | Respirable dust |