Why Do Religious Candles Turn Black?

As candles burn, smoke and soot may cause the glass to look black.

It can be a little disconcerting to burn a white candle and have it turn gray or black. This event is natural, however, and is simply caused by the candle elements burning.

Candle Composition

Most candles are made of paraffin wax or have a percentage of paraffin wax in them. Even beeswax candles may be almost half paraffin wax, unless the candle is labeled "100-percent beeswax." Paraffin is a petroleum byproduct and as such will smoke when it burns. Candle wicks are made from cotton braid; sometimes there is a wire or paper core in wick. Both paper and cotton smoke when they burn.

Effects

Wax, type of wick, size of the wick and size of the candle all affect the amount of smoke and soot that a burning candle creates. Candle makers must be careful to choose appropriate wicks when crafting candles. A wick that is too small is more likely to smoke, so a larger diameter candle requires a wider wick to burn well. On the other hand, a wick that is too large will make the candle burn quickly.

Expert Insight

When a white candle turns black when burning, it is simply smoke and soot in the air from the candle flame sticking to the candle. You may see black spots that look like pieces of dirt in the wet wax around the wick. The outer edge of a religious candle may also start to turn blackish. This is in part a reaction of the petroleum product heating.

Some candles, including 100-percent beeswax candles, advertise as "clean burning." This means they create little to no smoke and soot.

References

• Candle Home: What Candles and Wicks are Made of
• Querycat: Candle Black