How to Fix Candle Tunneling, Frosting & Sinkholes (Complete Troubleshooting Guide)

Every candle maker hits the same wall in their first 90 days. Candles look great in the mould, then tunnel when burning. Or frost overnight in the jar. Or develop deep sinkholes in the centre. Or the wick mushrooms and smokes.

None of these are deal-breakers. All of them are fixable with the right adjustment. This guide walks through the 10 most common candle making problems and how to fix each — written from years of supplying Indian candle makers at Bloom Creations.

Problem 1: Tunneling

What it is: Candle burns straight down the middle, leaving thick walls of unburned wax around the edge. Looks like a tunnel.

Why it happens: Wick is too small for the candle diameter. The flame creates a small melt pool that does not reach the edges.

How to fix it:

  • Size up your wick by one thickness. For a 7 cm diameter container, use a wick rated for 7–9 cm vessels (not 5–7).
  • Run a “first burn rule” reminder card with every candle you sell: burn for 2–3 hours on first lighting so the entire top surface liquefies. Subsequent burns will follow this pattern.
  • If a customer already has a tunneled candle: tell them to wrap aluminum foil around the top of the candle for 30 minutes while burning. Recovers the wax to a flat surface.

Problem 2: Frosting

What it is: White crystalline film that appears on the surface or sides of soy candles. Looks like a powdery coating.

Why it happens: Natural property of soy wax. The wax molecules recrystallize as temperature changes. Soy wax does this. Paraffin does not.

How to fix it:

  • Pour at a higher temperature — try 75–80°C instead of 60–65°C.
  • Cool candles slowly — do not put hot candles in front of a fan or in AC airflow.
  • Store finished candles in a temperature-stable environment (avoid cycling between 20°C and 35°C).
  • Switch to a soy wax blended with paraffin if frosting is a deal-breaker for your brand positioning.
  • Marketing tip: some boutique brands market frosting as “proof of pure natural soy wax.” True. Educate the customer instead of fighting the wax.

Problem 3: Sinkholes (Cracks in the Centre)

What it is: A deep crater forms around the wick as the candle cools, sometimes with cracks running from the wick to the edge.

Why it happens: Wax contracts unevenly as it cools — outside hardens first, inside is still liquid and shrinks. Cavity forms.

How to fix it:

  • Pour a small “top-off” layer 1–2 hours after the main pour. Reheat 100–150g of wax, pour just enough to cover the sinkhole.
  • Lower your pour temperature. Hotter wax contracts more.
  • Use a heat gun for 30 seconds on the finished candle top to remelt and smooth.
  • For deep sinkholes in pillar candles: poke a wooden skewer down into the candle from the top in 3–4 spots before the wax fully hardens. This releases trapped air and reduces sinkholes.

Problem 4: Wet Spots (Glass Candles)

What it is: Visible patches where the candle wax pulls away from the glass jar. Looks like clouded patches on the side.

Why it happens: Wax contracts as it cools and separates from cold glass. Cold jars worsen this.

How to fix it:

  • Pre-warm glass jars to 40–50°C before pouring. Place them on a warm tray or in a low oven (turn off before placing).
  • Pour at slightly hotter temperature (75–80°C).
  • Let candles cool slowly at room temperature, not in airflow.
  • Soy + paraffin blends have fewer wet spots than pure soy.

Problem 5: Weak Scent Throw

What it is: Candle looks great, burns clean, but you can’t smell it from 1 metre away.

Why it happens: Several causes — most common is undersized wick (small melt pool), insufficient fragrance load (under 6%), under-cured candle (poured 2 days ago, burned today), or low-quality fragrance oil.

How to fix it:

  • Cure candles for 7–10 days minimum before burning or selling. Soy candles need this for full scent development.
  • Bump fragrance load to 8–10% (test, do not exceed supplier maximum).
  • Size up the wick to create a larger melt pool.
  • Test your fragrance oil quality (see our fragrance oil guide).

Problem 6: Mushrooming Wick

What it is: Wick develops a black ball / mushroom shape at the top after burning. Drops carbon into the wax.

Why it happens: Wick is too big for the wax/fragrance load. Excess fuel causes carbon buildup.

How to fix it:

  • Size down the wick by one thickness.
  • Trim wicks to 5–6 mm before each burn (customer education).
  • If using cotton wicks at high fragrance loads (10%+), switch to wooden wicks — they handle high fragrance loads better.

Problem 7: Black Soot When Burning

What it is: Black smoke or carbon deposits on the inside of glass jars or near the wick.

Why it happens: Wick too large, candle in a draft, wax-fragrance combination doesn’t burn cleanly, or wick not trimmed.

How to fix it:

  • Size down the wick.
  • Place candles away from drafts (AC vents, open windows).
  • Trim wick to 5–6 mm before each burn.
  • If switching wax types helps, soy generally produces less soot than paraffin.

Problem 8: Candle Pulls Away from Mould During Demould

What it is: Candle gets stuck inside silicone mould, tears apart when you try to remove it.

Why it happens: Demoulded too early, high fragrance load causing oil bleed and stickiness, or mould has been damaged.

How to fix it:

  • Wait 24 hours for pillar candles before demoulding. 48 hours for large candles.
  • Refrigerate the mould for 20 minutes before demoulding — shrinks the wax slightly, easier release.
  • Use mould release spray if fragrance load is high.
  • Inspect mould for tears or damage. Replace if leaking.

Problem 9: Top of Candle is Bumpy / Uneven After Cooling

What it is: Surface of the candle is not smooth after cooling — lumpy, cratered, or has small bumps.

Why it happens: Air bubbles trapped under the surface, or cooling too fast.

How to fix it:

  • Tap the mould gently on the table 3–4 times after pouring to release air bubbles.
  • Use a heat gun for 20–30 seconds to remelt the top surface, then let it set flat.
  • Cool candles in a covered space — a draft or rapid cooling creates surface tension issues.

Problem 10: Fragrance Oil Separating From Wax (Oil Pockets)

What it is: Small pools of oil visible inside the candle after cooling, or oil leaking from the mould.

Why it happens: Fragrance load exceeds the wax’s maximum absorption capacity, or fragrance was added at wrong temperature.

How to fix it:

  • Add fragrance at 82–85°C, not above. Stir gently for 2 minutes.
  • Reduce fragrance load to manufacturer’s recommended maximum.
  • Switch to a wax with higher fragrance absorption capacity if you need stronger throw (some soy waxes hold 10–12%, others only 8%).

The Master Troubleshooting Checklist

When you have a candle problem, work through these questions in order:

  1. What temperature did you add fragrance? (target 82–85°C)
  2. What temperature did you pour at? (target 65–75°C for soy containers)
  3. What fragrance load did you use? (target 6–10%, never above supplier max)
  4. How long did you cure before testing? (minimum 7 days for soy)
  5. What wick size for what candle diameter? (use supplier sizing chart)
  6. Were the containers warm or cold during pour? (warm reduces wet spots)
  7. How did the candle cool? (slow, draft-free is best)

90% of problems trace back to one of these seven variables. Get them right, and your candle making becomes consistent.

Frequently Asked Questions

Why does my candle tunnel even with a thick wick?

Likely a first-burn problem. The candle needs to be burned long enough to liquefy the entire top surface on its first burn (2–3 hours for a 7 cm jar). Once it tunnels, every subsequent burn follows the same tunnel.

Is frosting on soy candles a defect?

No — frosting is a natural property of pure soy wax. It does not affect burn quality or scent throw. Many premium brands market frosting as a sign of natural soy.

How do I cure candles properly?

Place finished candles in a dust-free, temperature-stable space (18–25°C). Leave undisturbed for 7–10 days. Soy wax candles develop full scent throw only after this cure period.

What is the best wick size for my candle?

Match wick to vessel diameter. Most cotton wick brands publish sizing charts. As a rough rule: for soy candles, a wick rated for the next diameter up (slightly oversized) gives the best melt pool.

Why do my candles smell great when not lit but have no scent when burning?

This is a hot throw problem. Causes: wick too small (insufficient melt pool), fragrance load too low, or fragrance oil that has good cold throw but weak hot throw (cheap or perfume-grade oil). Read our fragrance oil guide for diagnostics.

Where can I get supplies and replacement parts when something fails?

Bloom Creations stocks 700+ candle making supplies — wax, wicks, fragrance oils, moulds, dyes, tools, containers. Replacement of any item ships pan-India. Browse our catalog.

Written by the Bloom Creations team. Read our complete guide to starting a candle business in India for the bigger picture.

Back to blog