How Do I Fix Rough or Bumpy Candle Tops?

A rough or bumpy top is mostly about how the wax cooled. CandleScience says rough tops are particularly common in soy wax candles, and names three causes: temperature shifts, air in the wax, and some fragrance oils. You can smooth a set candle with a heat gun or a thin second pour, and you can cut down on it in the next batch by slowing the cool and handling the wax more gently.

What causes rough tops?

CandleScience's smooth-tops page lists three causes:

• Temperature shifts. Cooling too fast, or a big gap between the wax and the air around it, can form larger crystals. Its soy troubleshooting guide puts it as cooling that is too fast or too slow.
• Air in the wax. Bubbles rising as the wax sets can leave holes and texture.
• Fragrance oil. Some oils are more likely than others to cause rough tops, depending on the recipe.

If the fault is a dip or a split instead, see our guide on sinkholes and cracks. White crystals across the surface are frosting, which has its own guide.

How do I fix a rough top on a candle that has set?

1. Let the candle cool and set fully.
2. Pick a fix: a heat gun or a thin second pour.
3. Heat gun: melt the surface just enough to level it. CandleScience's smooth-tops page says a few seconds of high heat. Its soy guide says low heat, held fairly close, until the wax melts slightly. The sources differ, so start low and short on a spare candle. Makesy says to use an entry-level heat gun, move it in a quick circular motion and keep it off the wick. It warns that an industrial heat gun can burn off the fragrance's top layer.
4. Second pour: hold back some wax when you pour. CandleScience's soy guide says to re-pour about 1/8 inch (3 mm) of melted wax over the top. Lone Star says to re-melt the held-back wax and make a thin second pour to level it.
5. Leave the candle still. Makesy says not to move it after heating so the surface stays flat.

Makesy says never to use a blow dryer. CandleScience says a hair dryer can work in a pinch, but its wide airflow can blow hot wax onto you or your workspace.

How do I get smooth tops in the first place?

This is the question most makers ask, so here it is in one place. All of it comes from CandleScience's smooth-tops page unless I say otherwise.

• Stir gently when you add fragrance, and pour slowly into the jars. Both reduce bubbles.
• Start with your wax maker's pour temperature. If tops come out rough, try pouring 5 to 10 degrees F (3 to 6 C) warmer. The soy guide says to adjust by 5 degrees either way. Treat the direction as something to test, since the sources do not agree for every wax.
• Keep the room steady. CandleScience says 68 to 72 degrees F (20 to 22 C).
• Let air under the jars. Stand them on racks, or on corrugated cardboard, so air can circulate underneath.
• Cool slowly. Lone Star says slow cooling produces the smoothest tops, and that fans, vents and movement are best avoided.

See our guides on pouring temperature and when to add fragrance oil.

Worked example: fix it or sell it as a second?

You pour 24 jars and 9 come out rough. All numbers are examples. Using a heat gun takes about 2 minutes per jar, so 9 x 2 = 18 minutes. At $20 an hour, 18 minutes is 18 / 60 x 20 = $6.00 of your time, or $6.00 / 9 = about $0.67 a jar.

Now compare. Marking those 9 down by $4 each from a $24 price loses 9 x $4 = $36. Fixing costs about $6 of time. So fixing wins, as long as the fix works and does not burn off the fragrance. To stop paying that cost, find the cause. Here 9 of 24 is 37.5 percent. Change one thing per batch, such as a slower cool, then a steadier room, then a 5 degree shift in pour temperature, and watch which one moves that number.

Common mistakes

• Using a blow dryer or an industrial heat gun.
• Holding the heat gun in one place until the fragrance burns off.
• Stirring hard after adding the oil.
• Cooling by the window, near a fan, or in a cold room.
• Changing three things at once, then not knowing which one worked.

Questions

Can I fix a rough top without a heat gun?

Yes. A thin second pour of held-back wax works, per CandleScience and Lone Star. You need to keep a little wax back when you pour.

Do rough tops change how the candle burns?

I did not find a source in the pages I read that says they do. Burn-test your candles in your own jar with your own wick and wax as you would any other.

Why are only some of my jars rough?

This is my reading, not a quote from a source: jars near a draft or on a cold surface may cool faster than the rest, which fits CandleScience's point about temperature shifts. Note where each jar sat, and keep the room steady.