Howell Labs flash

Composition

25  
Aluminium (dark pyro)
25  
Sulfur

Description

DANGER: Chlorate and sulfur/sulfide mixes are known to be very sensitive to shock, flame, spark and friction.

DANGER: Chlorate flash mixtures decompose faster than perchlorate flash mixtures and are more sensitive to shock, flame, spark and friction.

Source: 
Howell Labs