Your questions, answered.
Clubbing, or “mushrooming” as it is referred to in extreme cases, is caused by incomplete combustion of the wax and fragrance oil. This can occur when too much fuel is being delivered to the wick compared to the amount of oxygen being supplied, leading to the formation of carbon deposits on the wick. It should be noted that for highly scented candles, clubbing cannot usually be completely avoided.
Minor clubbing is very common and is not normally a cause of concern. More pronounced mushrooming is often a sign that a candle is overwicked, so down-wicking will reduce fuel flow and should reduce the effect, although down-wicking will create a smaller melt pool.
Sometimes it will be necessary to change to a different wick family to reduce clubbing or mushrooming. Different wick families will have different chemical treatments, or different constructions, which are suited to different candle systems. For example, LX wicks are best suited to paraffin candles with moderate scent loads, whereas V wicks are designed to deal with heavy fragrance loads.
Occasionally, a particular fragrance oil will cause clubbing regardless of the wick used. In such cases, a different wax blend may improve the situation. Candle Shack's fragrance oils are developed by expert perfumers for use in candles, but fragrance oils from other suppliers may not be compatible with candle making.