Why Does Candle Wax Shrink?

Why Does Candle Wax Shrink

If you are having problems with your candle wax shrinking down in the middle, you might be wondering why this happens sometimes and how you can stop it. It’s very annoying, and spoils all the hard work that you go to in choosing a beautiful container and making your candle look lovely, because you’ll have a hollow in the center.

Shrinkage can happen for a number of reasons, but it is a common issue with glass, because the temperature of your container (the glass jar) is different from the temperature of your wax as you pour it. This causes the wax to pull toward the edges of the container as it cools. Other factors include pouring temperature and ambient temperature.

Unfortunately, wax that has been poured will almost always have some shrinkage, and your options are to re-pour it, or to use a heat gun to smooth out dimples and get a beautiful finish. You can also buy a kind of wax that is designed to be one-pour, but many users find even this suffers from shrinkage.

Why Does Candle Wax Shrink?

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This phenomenon annoys candlemakers everywhere, ruining good candles and meaning a lot of extra hours double-pouring hot wax to get rid of the problem. So, why does it happen? What makes this shrinkage?

It’s worth noting that this is not the shrinking (or “tunneling”) that occurs when you burn the candle for the first time, but the sinking that happens when you have first poured the candle and allowed it to set.

What was a beautiful, smooth surface suddenly has a big dent in the top. This will usually appear around the wick and it can be very annoying, because it ruins a beautifully poured candle, and involves heat guns or repeat pouring to fix it. You may find you spend ages getting the surface of a candle smooth, but why does it occur in the first place?

The shrinkage essentially happens because as your candle’s wax starts to cool down, it contracts, and it starts to stick to things. The sides will cool quickly, because they are in contact with the most cool air, and they will begin to adhere to the glass you have poured the wax into.

Because the wax is contracting and sticking, it will pull toward the sides of the jar, and this leaves less wax in the center, which is cooling more slowly. Gradually, a dip will form, as more wax is pulled to the cold, contracted sides, and less is left in the middle.

Annoying though this may be, it’s unfortunately just part of candle making, but there are a few things you might be doing that could make it worse. Knowing about these might help you to reduce the overall issue you’re facing.

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Avoid a High Pouring Temperature

If you can get away with pouring your candles at a lower temperature, you may find that this helps. Pouring at a temperature that is too high increases the amount of shrinkage and can result in candles that just don’t look as nice because they don’t adhere properly to the jars or they have a dip in the center.

A lower pouring temperature will reduce the contraction, and leave you with a more even surface across the whole top of the candle. However, there is only so far that you can push this, of course, because a very low pouring temperature will run into other issues, like failure to set properly.

You can experiment with pouring temperatures and find out what works for you, but don’t do this if the batch is a critical one – stick to the recommended temperatures, and experiment later.

Avoid Cooling the Wax Too Quickly

You may also find that it helps if you slow down the cooling process. You can set your candles somewhere warm after they have been poured, and the wax will still cool, but much more gradually. Because the molecules are contracting more slowly, this should reduce the dip in the center.

The dip will probably still be there, because even in a warm environment, the outside will cool more quickly than the inside, but it should reduce how pronounced it is.

Temperature is a very important aspect of candle making, so ensure you have an accurate thermometer and use it carefully. Do not just “wing it” or your results won’t be great. You can still make candles, but they will often be a little lumpy or “abstract” as a result.

Don’t Use Cold Jars

Cold jars can be a problem for two reasons. Firstly, they are at risk of cracking when you pour the hot liquid wax into them because the temperature change will shock the glass.

Secondly, even if they don’t crack, they will cool the outside of the wax much more quickly than the inside, and this exacerbates the shrinkage issue. The cold glass will make the wax close to it contract very fast, and this will pull wax from the center of the candle toward the edge, forming a dip around the wick in the middle.

The same goes for other containers if you aren’t pouring the wax into jars. A cold container, a cold room, or a very high pouring temperature increases the intensity of the temperature change between the inner wax and the outer wax, and the more pronounced this is, the more significant the dip in the center will be.

Final Thoughts

Candlemakers all have to handle the dip in the center of their candles, and while it’s annoying, it is a part of the process you will have to deal with. However, you can reduce it by being careful about the temperature exchange.

If you can, lower the temperature of your wax a little, and increase the temperature of your containers and the ambient temperature in which the candles are setting. Don’t put candles in the fridge or the freezer to set, as this will make the dip a lot worse!

You probably can’t get rid of the dip without a heat gun or repeat pouring, but you can reduce it via careful temperature control.

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