Candle Troubleshooting: Frosting, Sink Holes, Wet Spots and Cracks

Most candle defects are read backwards. The surface you see after the candle sets is the last step in a chain that started with pour temperature, room temperature, and the container. Changing the wax is the most expensive response and usually the wrong one. This guide walks through the four defects that generate most of the emails we receive — frosting, sink holes, wet spots and cracks — what each one is telling you, and the order to work through them so you fix one variable at a time instead of four at once.

Read the defect before you change anything

Two questions sort almost every defect interview.

• Is it cosmetic or functional? Frosting and wet spots are usually appearance issues: the candle still burns correctly. Cracks, tunnelling and a persistent crater can affect how it burns. Cosmetic problems cost you shelf appeal; functional problems cost you customers. They deserve different urgency.
• When did it appear? A defect visible straight after pouring has one set of causes. One that appears after two weeks on a shelf has another. Note the date you first saw it.

Write both answers down before touching the formula. Then change one thing at a time — a defect that disappears after three simultaneous changes has taught you nothing.

Frosting: the white film on soy candles

Frosting is a white, crystalline film on the surface, or occasionally the sides, of a soy candle. It is not mould, and it is not contamination. It is the wax's crystal structure reorganising, and on natural waxes it is a normal behaviour rather than a sign of bad material.

What influences it:

• Cooling speed. Wax that cools very quickly can frost more than wax that sets gradually in a stable room.
• Temperature swings after setting. Cold nights and warm days in a warehouse move the wax through the range where crystals rearrange.
• Fragrance and dye load. Higher loads can make frosting more visible on the surface.
• Storage time. Some frosting simply develops with time, which is why a candle judged on the day it was poured is judged too early.

What to try, in order: slow the cooling by pouring into a room-temperature container in a draft-free space, stabilise where finished candles are stored, and only then review your fragrance load. If the frosting is light and the candle burns well, treat it as a cosmetic issue and decide whether it matters for your packaging — an opaque tin never shows it.

Sink holes and surface dips

A sink hole is a dip or crater in the top surface, sometimes with a void underneath. It exists because wax contracts as it cools from liquid to solid, and the centre of a container cools last.

The standard fix is a second pour: once the candle has set and the dip has formed, warm a little extra wax and top the candle up. The top-up wax bonds to the surface below it and gives you a flat top. This is normal production practice, not a workaround.

The variables worth checking before you change wax:

• Pour temperature. Pouring hotter increases the amount of contraction as the candle sets.
• Pour-area temperature. A cool, drafty room pulls heat out unevenly, which makes the dip deeper on one side.
• Container and volume. A wide container with a large open surface dips more than a narrow jar.
• Cooling insulation. Some makers set candles under a light cover to slow the surface cooling.

A dip that persists after a correct second pour, across several batches, is worth a conversation with your supplier — but only after the pour and cooling variables are ruled out.

Wet spots: wax pulling away from the glass

A wet spot is a patch where the wax has separated from the container wall, leaving a visible gap that looks like moisture. It is not water. It is contraction and adhesion: the wax shrinks slightly more than the glass, and where it pulls away, the gap reads as a pale or shiny patch.

Wet spots are cosmetic. They do not affect burn quality.

Worth checking:

• Container temperature. Pouring warm wax into a cold jar increases the temperature differential and the pull-away.
• Container surface. Glass straight from a dusty shelf may not bond as cleanly as clean, room-temperature glass.
• Cooling speed. Fast, uneven cooling increases the chance of separation.
• Wick centring and the wax column. Sometimes the gap is only visible where the wax has shrunk against a curved wall.

Because it is cosmetic, the decision is commercial: for clear glass and premium presentation, it matters; behind an opaque label or a tin, it usually does not.

Cracks and other set-time splits

Cracks are fractures in the set wax, often radiating from the wick or running along a layer boundary. They show up most often when cooling is fast or uneven, and when a candle is poured too cool — the wax is already thickening as it fills the container, so layers do not knit together.

Look at:

• Pour temperature too low, which creates visible flow lines and weak boundaries.
• Pour temperature too high, which increases contraction and stress as the candle sets.
• Rapid cooling, for example from a cold draft or a chilly floor.
• Layer work. Coloured layers and embedded objects introduce boundaries where stress concentrates.

For layered and novelty formats, especially transparent jelly wax work, layer temperature control matters more than it does in a single-pour container candle.

The troubleshooting order that saves wax

Working in this order keeps you from changing the wax for a problem that lives in your process.

1. Confirm the wick. Wrong wick size produces tunnelling, soot and a poor melt pool that are often blamed on wax. 2. Confirm pour temperature and room temperature. Record both, not just the wax temperature. 3. Confirm cure and storage conditions. Two to four weeks in a stable room; note the actual range, not the average. 4. Confirm fragrance and dye load against the supplier's reference mix — our specification sheets list a starting ratio for the wax you bought. 5. Test the same batch again before switching batches. A single pour can misbehave for reasons that do not repeat. 6. Then change the wax, and change one batch at a time.

Steps one to five cost you nothing but an afternoon. Step six costs you a production run.

When the wax is actually the variable

Sometimes it is the material. A measured melting point that has drifted outside the supplier's stated tolerance changes how the wax sets, and no amount of pouring discipline will fix it. That is what a batch COA is for: it lets you compare the wax you have against the values you approved. If your numbers repeat but the behaviour does not, ask the supplier for the COA of the suspect batch and compare it with the previous one.

If you are troubleshooting against a batch and want the measured values, send us the batch number — we hold the QC record for every batch we ship and reply within 24 hours. And if you have not yet settled on a base wax, the wax comparison guide covers which format suits which product before you start chasing defects that belong to the wrong format.