Why is my candle tunneling, frosting, or sweating?

Soy and soy-blend candles are full of small cosmetic faults — and a couple of real performance ones. The good news is that almost every common flaw has a short list of causes. Here are the six you'll meet most, what each one is, and where to look first.

Tunneling

What it is: the candle burns straight down the middle, leaving a ring of unmelted wax stuck to the glass.

Cause: the wick is too small to push a full melt pool to the edge — or the candle was blown out before the first burn reached the glass. Container wax has "memory": it re-melts only as wide as its first burn, so an under-burned first session locks in tunneling forever.

Fix: size the wick up one step, and on the first burn let it run until the whole top is liquid (usually 2–3 hours). This is a real performance flaw, not cosmetic — start with the wick.

Frosting

What it is: a white, crystalline, slightly powdery film on the surface or sides — most visible in dyed candles.

Cause: it is natural crystallization of soy wax as it cools, a sign of pure soy, not a defect. It does not affect scent throw or burn.

Fix: you can reduce it — pour a little warmer, warm your vessels before pouring, and cool slowly and evenly — but you can't fully eliminate it in pure soy. Many makers simply label it as a hallmark of natural wax.

Sweating (oil on top)

What it is: beads of oil pooling on the candle surface.

Cause: usually too much fragrance oil — past the wax's maximum load, the excess can't bind and seeps out. Heat and temperature swings make it worse.

Fix: drop the fragrance load to within your wax's rated maximum, and store finished candles somewhere cool and stable. If you were already at-or-over the max, this is the first thing to cut.

Wet spots

What it is: patches where the wax has pulled away from the glass, looking like air bubbles against the side.

Cause: the wax cooled and contracted unevenly, losing contact with the glass. Cosmetic only — burn and scent are unaffected.

Fix: warm the vessels before pouring and let candles cool slowly at room temperature, away from drafts and cold surfaces. Hard to eliminate entirely in glass.

Sinkholes & rough/lumpy tops

What it is: a cavity around the wick (sinkhole), or a bumpy, uneven surface.

Cause: wax shrinks as it sets, and pouring too hot or cooling too fast exaggerates it. Rough tops often come from pouring too cool.

Fix: pour within your wax's recommended pour-temperature range, and use a heat gun to gently re-melt and smooth the top, or do a small second "top-off" pour to fill a sinkhole.

The short diagnostic

Related: How to choose a candle wick size · How much wax and fragrance for a candle?