Also known as cavities or depressions, (I call them nostrils) can occasionally occur in candles during the cooling process, disrupting the otherwise smooth and visually appealing surface. While they can be frustrating for candle makers, addressing and preventing sink holes is an essential skill to ensure the production of high-quality candles. Here are tips on how to fix sink holes in candles and prevent them from occurring in the first place.
1. Understanding the Causes: Before diving into solutions, it’s crucial to understand the common causes of sink holes. Rapid cooling, temperature fluctuations, and the type of wax used are often contributing factors. Incomplete adhesion between layers of wax can also lead to sink holes.
2. One of the primary culprits of sink holes is a rapid and uneven cooling process. To counteract this, adopt a slow and controlled cooling method. Make sure that your room temperature is around 18c. Avoid exposing candles to extreme temperature changes, although it’s tempting to pop your candle in the fridge for fast setting – don’t! as this can lead to uneven cooling and, subsequently, sink holes. Ideally you want your candle to set from the bottom up. When it cools from the top it sets around the wick and sides first and the set wax falls down into the liquid wax underneath. Read – How to size your candle container
3. If sink holes have already formed, you can melt some wax and top up. Once the initial pour has cooled, reheat a small amount of wax and pour it into the depression, filling the sink hole. (watch out for bubbles, grab a cocktail stick to pop them). Repeat this process until the sink hole is level with the surrounding wax. This technique requires precision to avoid causing new issues like bubbles, so patience and careful observation are key.
4. Preventing sink holes can be as crucial as fixing them. Consider adopting the double-pour method, where you initially fill the container or mold partially, let it cool, and then pour a second layer. This approach minimises the risk of sink holes by allowing each layer to bond effectively, resulting in a more even and structurally sound candle.
5. Ensure that the wick is centre and straight in the mold or container. An off-centre wick can create uneven cooling, contributing to the formation of sink holes. Use wick holders or other tools to keep the wick in place during the cooling process. How to select the correct size wick
6. The type of wax used plays a significant role in sink hole prevention. Some waxes are more prone to sink holes than others due to their composition and melting points. Experiment with different wax blends to find one that minimises the risk of sink holes in your candle-making process.
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