Flowers of sulfur refers to sulfur that has been purified and shaped into flakes or pellets. The flakes may be combined with wax and formed around a wick, or the pellets may be placed in heatproof tins with rolled-paper wicks. When burned in an enclosed area, these candles fill the air with sulfur fumes, killing all insects in the area. As less messy and less troublesome means of fumigation have been developed, flowers of sulfur candles have become less common.
Sulfur, also known as sulphur or brimstone, is a nonmetal element that is crystalline in structure. It is pale-yellow in color, but it turns blood-red when burned. It does not mix well with water, though some forms are sold as wettable powders. Sulfur is usually found in or near areas of volcanic activity, including hot springs and active volcanoes.
The use of sulfur can be traced back to the ancient Egyptians, who burned it to fumigate granaries and used it in powdered form to treat skin irritations and other health issues. The Greeks and Romans are also known to have used sulfur for both medicinal and fumigant purposes. Gardeners use the powdered form as a soil amendment for acid-loving plants, and people with greenhouses may use the pelletized "flowers of sulfur" candles to fumigate empty greenhouses. Until recently, the candles were recommended as a fungicide as well as an insecticide.
Use as a Fumigant
When the purified form of sulfur known as flowers of sulfur is combined with wax and formed around a wick or gathered into a tin and burned, it produces clouds of smoke containing sulfur dioxide. This gas readily permeates any enclosed area, filling the smallest nooks and crannies and killing whatever it contacts there. Flowers of sulfur candles are also sometimes used in wine-making both to disinfect the casks before they are filled and to stop fermentation in partially filled casks.
The fumes of burning sulfur are extremely irritating to the respiratory tract, and can be fatal to all pets, including fish and birds. People who inhale the fumes can become very ill, and it is for this reason that flowers of sulfur candles are seldom recommended in modern pesticide treatments. While there are rumors that these candles are effective against bedbugs and fleas, the fact is that they are far more dangerous and much less effective than the modern treatments used by professional pest-control personnel.