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Why Does My Candle Jar Turn Black?

Jan. 07, 2023

Scented Candle

 Scented Candle

You have been burning the candle and love the new scent, but you notice a thin grey film forming on the top of the candle glass jar. With each burn, the build-up gets worse until you have a black ring at the top of the candle. Although unsightly, there is a perfectly normal explanation for this black deposit and it is very easy to prevent and clean. Read on to find out what causes candle glass to turn black, how to prevent it from happening and how to clean up the build-up.


What causes candle glass to turn black?

The darkening of candle glass jars is due to the build-up of soot. Soot is produced by any type of candle, although it is more common in some types of wax, such as paraffin. The production of soot is the result of an incomplete combustion reaction and it can be caused by several different factors. One of the main reasons is that the flame of the candle is too large, which in turn is caused by a longer wick. A longer wick and larger flame mean that more wax will be melted, which gives the candle more fuel.

Candle Jar

 Candle Jar

How can I prevent the candle glass from turning black?

Thankfully, soot formation is not inevitable and there are several steps you can take to stop soot from forming before it starts. The first is to trim the wick to an eighth to a quarter of an inch before each burn (make sure the candle has cooled completely before doing this). You can start by using scissors to do this, but you may want to get a special wick trimmer so you can continue trimming as the candle burns. Trimming the wick keeps the flame small and ensures it is evenly shaped, helping to prevent incomplete combustion.


If the wick moves during the burning process, you should also re-position it while the wax is still soft. You can use a wick trimmer or other tool to push it back into place. Don't use your fingers or you may burn yourself. You should also keep the candle away from vents, draughts, and other things that could cause flames to sputter or burn unevenly. Keep the candle in a safe place and do not allow it to be disturbed. It's normal for the candle's flame to wobble a little, but if it does go in and out, or is unevenly shaped, try moving the candle to a new position.

Soy Wax Candle

Soy Wax Candle

How do I clean the black candle glass?

Despite your best precautions, your soy wax candles may still form soot. If your candle glass has turned black, it is best to clean it regularly to prevent soot build-up. The more soot there is, the more difficult it will be to clean. Before cleaning your candles, blow out the flame and allow the wax and candle jar to cool completely. Wet a paper towel and wipe it over the soot until it dissipates. If the soot is really stubborn, you can use alcohol instead, which will cut through the build-up. Allow the candle to dry completely before burning again.


If you have burned the candle all the way through and want to reuse the candle jar, you can also use soap and water to remove the wax from the candle. Firstly, you need to remove the candle wax from the candle jar. Soak the candle glass jar in some soapy water and then wipe it with a soft cloth until all the soot has come off. Allow the container to dry before re-using.

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