Why did my pillar crack, cave in or burn through the side?

Most pillar faults come from three places. Faults you see when the candle leaves the mold (cracks, voids, a sunken center, lines and mottling) come from pour temperature, cooling and the missing second pour. Faults you see when it burns (a wick that drifts, a flame that breaks through the wall, wax running down one side) come from the wick's size and position and from drafts. A pillar that burns through its side is a fire problem as well as a looks problem, so stop and change the wick. This page takes each fault in turn: what you see, what it means, and what to change, using the published notes of the wax makers wherever they address it.

Find your problem

Faults you find when the candle comes out of the mold

Cracks

What you see. A fine crack running down the side, across the base, or radiating from the wick.

What it usually means. The pillar cooled too fast or unevenly: a cold room, a draft on one side, or too long in a fridge or freezer to help release. A thick candle cools from the outside in, and when the outside sets hard before the inside has shrunk, the stress has to go somewhere.

What to change.

• Cool undisturbed in a still, room-temperature space. Supplies for Candles gives about 25°C (77°F) for Kerawax 4600, with molds 1/4 to 1/2 inch apart [1].
• If you chill a mold to help release, keep it short; Supplies for Candles describes "a few minutes" in the fridge [1].
• Make the second pour while the candle is still warm, not after it is cold. A hot top-up into a cold candle sets up a hard boundary.

Air pockets and voids

What you see. A cavity under the skin at the base (the top of the pour), or holes inside the candle when you cut a test pillar in half.

What it means. As the candle shrinks, the surface skins over before the center has finished settling, leaving a hollow underneath. Supplies for Candles describes exactly this with Kerawax 4600: the base can skin over and leave a void [1].

What to change.

• When the candle is still warm with a set center, poke two holes near the wick through the skin, then make the second pour. Supplies for Candles pours again at 60°C (140°F) for 3 and 4 inch pillars [1].
• Pour slowly and steadily so less air is folded in, and tap the side of the mold gently after pouring to bring bubbles up.
• Cut one test pillar from each new wax or mold in half to see what is inside. A void near the wick changes how the candle burns.

A sunken center

What you see. A deep well around the wick after the first pour.

What it means. Normal shrinkage. CandleScience reported "significant shrinkage around the wick pin" with MP-137 and IGI 1239 pillars, and some shrinkage around the pin with IGI 6028 [2] [3] [4].

What to change. Plan for a second pour every time. CandleScience made MP-137's second pour at 190°F (87.8°C) and needed no third [2]. Fill only to the original level so no lip forms over the edge.

Jump lines

What you see. Horizontal lines or rings around the outside, often with a change between glossy and matte areas.

What it means. The wax was poured too cool, or the pour stopped and started. CandleScience found that MP-137 poured between 170 and 180°F gave a very smooth, very shiny finish, while below 170°F it showed jump lines and a split between matte and glossy areas [2]. With IGI 6028, pillars poured below 180°F had some jump lines [3].

What to change. Pour at the top of your wax's range (180°F for both of those waxes [2] [3]) in one continuous pour. Make sure the mold is at room temperature, not cold. A glossy wax will also show fingerprints; CandleScience notes MP-137's finish "will show fingerprints and imperfections easily" [2], so handle with gloves.

Mottling and frosting

What you see. A snowflake or marbled pattern on the outside (mottling), or a white crystalline film (frosting, mostly on vegetable waxes).

What it means. Mottling is crystal pattern in the wax, and with some paraffins it depends on temperature. CandleScience found IGI 1239's mottling "inconsistent" and dependent on wax temperature, with the second pour adding more mottling on pillar bottoms, and judged it more likely to mottle than IGI 1343 [4]. Some makers want mottling as a look; others want a smooth surface. Frosting is typical of vegetable waxes. CandleScience saw no frosting on IGI 6028 pillars after three months and attributes that to the paraffin in the blend [3].

What to change. For even results, hold your pour temperature and room conditions the same every time and record them. If you consider an additive to change the surface, take its rate and its stated purpose only from the additive maker's sheet; NuCera, for example, lists VYBAR 103 and 108 for paraffins melting at 58°C or above, used in pillars, tapers and votives, at 0.25 to 1.0 percent by weight [5]. Any additive means retesting the wick. Frosting on soy is covered on frosting on soy candles.

Faults you find when the pillar burns

Wick wander

What you see. The wick is off center at the top, or drifts as the candle burns down; the flame leans toward one wall.

What it means. The wick was not held taut and centered through the whole pour and cooling, or it bent in the second pour.

What to change. Seal the wick at the base and pull it taut to a wick bar across the top before pouring; check it after the second pour and again before the candle sets. Use a primed wick, which stays straighter. An off-center pillar wick is the most common route to guttering and blowouts below.

Blowouts

What you see. The flame melts through the wall and wax pours out of the side.

What it means. The wick is too large for the diameter, or off center, or the pillar is burning in a draft that pushes the flame to one side. This is the failure pillar wicks are chosen to prevent: CandleScience used the LX series in every pillar test because it "produces a smaller tighter flame which is essential to prevent blowouts or holes in pillar candles" [2].

What to do now and next. Put the candle out. Molten wax running from a pillar onto a surface is a burn and fire hazard, and a pillar must stand on a heat-resistant plate or holder; the National Candle Association tells consumers to use stable, heat-resistant surfaces [6]. Then test the next smaller wick in the same series, check centering, and burn tests away from drafts. If you sell to a buyer with a protocol, its fire criteria apply too; Kohl's Test Protocol 100-Z, for example, limits flame height to 3 inches and requires that nothing but the wick catch fire [7]. Those are one retailer's requirements, with no legal force.

Guttering

What you see. Wax runs out through a channel in the rim and down one side.

What it means. One side of the wall melted thinner than the rest, usually from a draft, an off-center wick or a candle that is leaning.

What to change. Burn tests in still air (NCA advises avoiding open windows, fans and air vents [6]) and on a level surface. Check the wick position. If the whole rim melts away evenly, the wick is too large; if only one side goes, look for the draft or the lean first.

Tunneling

What you see. The flame burns down a narrow hole in the center and leaves a thick wall that never melts.

What it means. For a pillar, a slightly unmelted shell is the goal, because it holds the pool in. A deep tunnel means the wick is too small for the diameter, or the burns are too short.

What to change. Test the next larger wick, and burn long enough each time for the pool to approach the edge. The general fixes are on why candles tunnel, and how far to move a wick after a failed test is on when to change the wick size.

Change one thing, then burn the pillar to the end

Every fix above is one variable. Change one thing per test, write it down, and burn the new pillar to the end on a heat-resistant plate before you change the next. GW 464's instructions put it as a general rule: every combination of container, wax, dye, fragrance and wick should be tested [8], and a pillar's combination includes its mold and its diameter. To rebuild the process from the start, go back to how to make a pillar candle; to choose a wick size methodically, see how to size a wick.

References

1. Supplies for Candles, Paraffin Pillar Blend Wax for Pillar Candle Making (Kerawax 4600 product page with instructions), updated October 22, 2026. https://www.suppliesforcandles.co.uk/?p=4368
2. CandleScience, Lab Notes: Paraffin Pillar Wax MP-137, undated (header image dated July 22, 2021), read October 22, 2026. https://candlescience.com/lab-notes-paraffin-pillar-wax-mp-137
3. CandleScience, Lab Notes: IGI 6028 Paraffin Soy Pillar Wax Blend, undated, read October 22, 2026. https://www.candlescience.com/learning/lab-notes-igi-6028-paraffin-soy-pillar-wax-blend
4. CandleScience, Lab Notes: IGI 1239 Paraffin Wax, undated (images dated 2018), read October 22, 2026. https://www.candlescience.com/learning/lab-notes-igi-1239-paraffin-wax
5. NuCera Solutions, VYBAR Polymers for the Candle Industry (brochure, version 12142021v1, copyright 2022). https://chasecorp.com/nucerasolutions/wp-content/uploads/sites/29/2023/05/NuCera_VYBAR_Candle_Brochure_v4-2.pdf
6. National Candle Association, Candle Safety Tips, modified August 12, 2025. https://candles.org/candle-safety/
7. Kohl's, Private Brands Performance Claims Test Protocols 100, Protocol 100-Z: Candle (including freestanding, taper, tealight, votive, filled and novelty candles), revised February 2025 (current revision; candle limits unchanged from 100-Y, February 2023), read October 22, 2026. https://link.kohls.com/content/dam/klink/100-Z-CANDLE.pdf
8. Voyageur Soap & Candle, Golden Brands GW 464 Soy Container Candle Wax (product page with manufacturer's instructions), undated, read October 22, 2026. https://www.voyageursoapandcandle.com/Golden_Brands_464_Soy_Wax_p/20264.htm