Well, really we want our candle magic to help light the way forward, not start the next forest fire! Candles have been used in magic since time immemorial; the simplicity of candle work is very appealing and vastly powerful.
No two candles, whether machine or handmade, will ever react the same way when lit for magical purposes. Each candle will be a unique experience. When dedicated and lit, each candle displays its unique personality that is shaped from your desires and is interpreted by the tiny fire elemental housed within the flame. Communication from each candle will vary slightly, depending on the task it is assigned and how well you have aligned your intention with it. It will also depend on whether you are paying attention to it.
Try this exercise the next time you do a candle spell:
As your candle burns, free your mind and concentrate on the candle. Watch how the smoke rises, the flame dances, and listen to the sound it makes. The smoke may rise to the east, or waft to the south, the flame may flare up or dwindle, and the sounds may be of a popping nature or you may be startled by the wax dripping down the side and pooling in the holder. Ask yourself how these actions relate to the magic you are casting. The answers you perceive are often startling and revealing about the true nature of your desires.
Take the time to pay attention to the flame during your next magical working and be open to the messages coming through!