Flares produce their light through the combustion of a pyrotechnic composition. The ingredients are varied, but often based on strontium nitrate, potassium nitrate, or potassium perchlorate and mixed with a fuel such as charcoal, sulfur, sawdust, aluminium, magnesium, or a suitable polymeric resin.
The main ingredients of flares include strontium nitrate (which provides the color-it burns with a bright red or orange-red flame), potassium perchlorate (a powerful oxidizer, which makes the strontium burn rapidly), and magnesium (which burns very brightly).