Armstrong's mixture is a highly sensitive primary explosive. Its primary ingredients are red phosphorus and strong oxidizer, such as potassium chlorate and potassium perchlorate. Sulfur and calcium carbonate might be present in small amounts, though other additives are also used. Commercially, Armstrong's mixture is used in extremely small quantities on the paper caps in toy cap guns. It has also been considered a suitable mixture for the primer used in guns after boron carbide has been added.
Because of its sensitivity to shock, friction and flame, Armstrong's mixture is an extremely dangerous explosive. Only about 10 mg of it is used per item of consumer fireworks. Depending on composition, conditions and quantity, Armstrong's mixture can explode violently in an enclosed space.
- J. B. Calvert. "Flash! Bang! Whiz!: An introduction to propellants, explosives, pyrotechnics and fireworks". Archived from the original on 15 November 2006. Retrieved 2006-11-11.
- US patent 3973502, Charles R Olsen, "Tube primer", issued 1976-08-10
- John Donner. "Impact Firecrackers" (PDF). Retrieved 2006-11-11.