stearic acid

Stearicacid is used for many different household products. It is used as a lubricant, a hardener, and an emulsifier, a chemical that allows oils and water to mix. Many common items contain stearicacid, including soaps, cosmetics and lotions, stick deodorants, and candles. In candles, it makes the wax more opaque, less clear, and less likely to drip.

It also hardens them and increases the melting point, so the candle will last much longer.