## Calcium sulfate

**Formula**
 
$CaSO4.x H2O$ where x= ~0.5 or 2

**Synonyms**
 
1. Hemihydrate = Plaster of Paris, Crystacal, Densite, Gypsum hemihydrate, Tiger stone
2. Dihydrate = Gypsum, Alabaster

**Description**
 
The hemihydrate (x=~0.5) is commonly known as plaster of Paris. The dihydrate (x=2) occurs as a mineral known as gypsum. Calcium sulfate can be used as a high temperature oxidizer in orange color compositions. Excellent strobe compositions can be made with it.

**Sources** 

Plaster can be used as is in strobe and exotic flash compositions, but is better to remove the water which is easily accomplished by heating. Plaster of Paris can be bought at hardware vendors and is often sold in hobby shops.

**Hazards**
 
Calcium sulfate dihydrate may act as an eye or respiratory irritant. Wear safety glasses and dust mask.
