Candle making combines craft, chemistry, and heat transfer in a simple object you can build by hand. A candle works because solid wax stores chemical energy, the wick delivers melted wax upward, and the flame vaporizes that wax so it can burn. Understanding wax, wick, and scent helps makers design candles that burn evenly, smell pleasant, and stay safe.
Small choices like wick thickness, fragrance amount, and container size can change how the whole candle behaves.
When a candle is lit, heat from the flame melts nearby wax and forms a liquid wax pool. Capillary action pulls this melted wax up through the wick, where it vaporizes and reacts with oxygen in the flame. Fragrance oils mix into the wax during pouring, then slowly evaporate from the warm wax pool and move through the air as scent molecules.
A well-designed jar candle balances fuel supply, heat output, melt pool size, and scent release.
Key Facts
- A candle flame burns wax vapor, not the solid wax itself.
- Capillary action pulls melted wax up the wick against gravity.
- Combustion of a hydrocarbon can be modeled as fuel + O2 -> CO2 + H2O + energy.
- Heat transfer in a candle includes conduction through wax and glass, convection in hot air, and radiation from the flame.
- Fragrance load = mass of fragrance oil / total wax mass, often written as a percent.
- For many jar candles, fragrance load is about 6% to 10%, but the safe amount depends on the wax and fragrance oil.
Vocabulary
- Wax
- Wax is the candle fuel, usually made of molecules that melt when heated and can vaporize near the flame.
- Wick
- A wick is a braided fiber strand that draws melted wax upward by capillary action and feeds fuel to the flame.
- Melt pool
- The melt pool is the layer of liquid wax that forms around the wick while the candle is burning.
- Fragrance load
- Fragrance load is the percentage of fragrance oil mixed into the wax before the candle hardens.
- Combustion
- Combustion is a chemical reaction in which fuel reacts with oxygen and releases heat and light.
Common Mistakes to Avoid
- Using too much fragrance oil makes the candle stronger automatically, which is wrong because excess oil can separate, clog the wick, weaken the flame, or create unsafe burning.
- Choosing a wick only by jar size is incomplete, because wax type, fragrance load, dye, and container shape all affect how much fuel reaches the flame.
- Pouring fragrance into wax when it is too cool can cause poor mixing, because thicker wax may trap oil unevenly and reduce scent throw.
- Burning a jar candle for only a few minutes on the first burn can cause tunneling, because the melt pool may not reach far enough across the surface before the wax hardens again.
Practice Questions
- 1 A candle maker uses 450 g of wax and wants an 8% fragrance load based on the wax mass. How many grams of fragrance oil should be added?
- 2 A jar candle contains 300 g of wax and burns at an average rate of 6 g per hour. Estimate the total burn time in hours.
- 3 Two candles have the same wax and fragrance oil, but one has a thin wick and the other has a thick wick. Explain how wick thickness could affect flame size, melt pool width, and scent release.