The first lighting of the candle is crucial. Soy wax has a "memory"—if you extinguish the candle before the melted wax reaches the rim of the container, the candle will "tunnel" in the same, too-narrow circle each time you burn it. The center will burn out, leaving a wall of unmelted wax on the sides.

A wick longer than 7 mm is one of the most common mistakes. A long wick burns with a large, unstable flame that produces smoke, burns the wax too quickly, and can cause the edges of the container to burn. Visible black smoke is almost always a sign of a wick that is too long.

Air movement causes the flame to waver sideways, causing the wax to melt unevenly and the wick to reach the walls of the container. Furthermore, uneven melting accelerates candle wear and can cause cracks in the glass or ceramic.

The candle's container heats up throughout the burn. After four hours, the temperature of the glass or ceramic can become so high that the wax begins to behave differently than it should—melting too quickly, and the fragrance dissipating more intensely but for a shorter time. Furthermore, an overheated wick "fungises"—a characteristic lumpy ember forms at the tip.

Soy wax is sensitive to temperature and light. Storing a candle in direct sunlight will cause the color to fade, the wax to change texture (known as "frosting"—white spots on the surface), and the fragrance to fade. A candle exposed to frost may crack or change its structure.