Some are scented and all come in a wide range of colors. Wax candles contain petroleum wax, vegetable wax, animal wax, or insect wax as the primary fuel. The wax may contain additives for color, fragrance, stability, or to modify the burning characteristics. Gel candles use liquids such as mineral oil, terpene-type chemicals, or modified hydrocarbons as their primary fuel. These candles also contain chemical agents to increase the viscosity of the fuel to the point where the candle has a quasi-rigid property.
Candles support one or more combustible wicks.
Metal is put in some wick cores to keep the wick standing straight when the surrounding wax begins to melt. The metal prevents the wick from falling over and extinguishing itself as soon as the wax fails to support it. Many companies use a braided wick, which consists of three smaller wicks wound together to provide some stiffness. Lead was commonly used as a core material until 1974 when the US candle manufacturing industry voluntarily agreed to discontinue use of lead in wicks. There are, however, still candles on the market that contain lead wick cores.