Strontium sulfate
From PyroGuide
Formula: SrSO4
Description: Strontium sulfate is used as a high-temperature oxidiser in some metal based red color compositions, and is particularly important in Ammonium perchlorate based red strobes.
Hazards: Strontium sulfate is not particularly dangerous or toxic.
Sources: Strontium sulfate may be precipitated from a solution of a soluble strontium salt, such as strontium nitrate or chloride, and a sulfate. Magnesium and potassium sulfate are both cheaply available as fertilizer and are convenient to use. The precipitated strontium sulfate is a very fine powder which may be rinsed by repeated washings with hot water, settling and decanting. A final washing in the filter with acetone or ethanol will allow it to dry quickly. Do not use sulfuric acid to precipitate strontium sulfate as this may result in the inclusion of acid droplets in the precipitated particles which can lead to spontaneous ignition of some mixtures.