How to Conduct Burn Tests to Adjust Your Wick

Adjusting the wick is key to achieving candles that burn cleanly, safely, and with good fragrance performance. A poorly chosen wick leads to tunneling, soot, smoke, unstable flames, or a weak scent. In this practical guide, you'll learn what burn tests are, which variables to control, and how to interpret results to find the ideal wick for your wax and container.

What are burn tests and why do they matter?

Burn tests are controlled experiments to evaluate how a candle behaves when burning: flame height and stability, melt pool size (area of liquid wax), soot and smoke production, and potential tunneling. Conducting tests allows you to:

• Select the correct wick diameter for your wax and fragrance blend.
• Verify compatibility between wick, wax, and container.
• Improve the longevity, safety, and olfactory quality of your candles.

Materials and preparation

You will need:

• Wicks of different thicknesses and types (braided cotton, paper core, wood, etc.).
• The wax you will use (soy, coconut, blend, paraffin, etc.).
• Representative containers or molds.
• Wax thermometer.
• Stopwatch or clock.
• Lighter or long matches.
• Notebook or card to record: wax type, container, wick, pouring temperature, times, and observations.

Preparation:

1. Label each sample with essential data.
2. Pour the wax following the same procedure and temperature for all copies.
3. Allow the wax to cure for the recommended time (usually 24–48 hours for many vegetable waxes).

How to perform the burn test (step-by-step)

1. First ignition — short test (2 hours)

• Place the candle in a draft-free area. Note the time.
• Observe the flame: stable or flickering? Conical shape or very wide?
• Measure the flame height (approx.).
• After 2 hours, extinguish the candle and measure the diameter of the melt pool.
• Note the presence of smoke, soot, or residue on the wick.

What to look for:

• Tall flame and soot: wick too thick.
• Reduced melt pool or tunneling: wick too thin.

2. Extended test — 4 hours or until 50% consumption

• Repeat with another sample and let it burn for 4 hours or until ~50% consumed.
• Observe the shape of the melt pool: ideally, it reaches near the edge, without overflowing.
• Detect mushrooming (black residue) or wick leaning.

3. Fragrance evaluation (throw)

• If using fragrances, evaluate the hot throw (during burning) and, if applicable, the cold throw (when extinguished and at rest).
• A wick that is too thin may not generate enough heat to release the fragrance; one that is too thick may alter or burn the notes.

Interpretation of results and adjustments

• Tunneling (small melt pool): increase wick size by one or two and retest.
• Excessive pool, tall flame, or soot: decrease wick size or try a type with less core.
• Wick extinguishes: use a thicker wick or check for contamination in the mixture.
• Poor scent: slightly increase the wick to raise the surface temperature; also check the fragrance percentage (without exceeding the recommended maximum).

Quick checklist for adjusting wicks

• Keep wax, volume, and conditions constant.
• Perform at least one short test (2 h) and one long test (4 h or 50%).
• Adjust the wick by 1 size per iteration and retest.
• Always document results and working configuration.

Common mistakes

• Changing too many variables at once.
• Only evaluating very short tests (some failures appear after hours).
• Not monitoring safety: never leave burning candles unattended.

Practical tips

• Start with the wax manufacturer's recommendations as a starting point.
• Create a test matrix (rows = wicks, columns = diameters/containers).
• If you sell candles, document the ideal wick per product for consistency and fewer returns.
• Wood wicks offer a distinct aesthetic but require fine-tuning; they often need a higher initial temperature.

Conclusion

Burn tests are a small investment of time that significantly improves the quality, safety, and olfactory experience of your candles. By following an organized method, you will find the right wick for each combination of wax, fragrance, and container.

If you want to learn everything about making candles — from material selection to advanced pouring techniques and burn tests — sign up for our workshops in Barcelona. At Vento Barcelona, we offer practical, guided classes where you can test, ask questions, and make your own candles with professional materials: https://vento.barcelona/talleres

We look forward to igniting your ideas and perfecting your technique!