Also called: scent throw, cold throw
Hot throw vs cold throw
In short
Hot throw is how strongly a candle scents a room while burning; cold throw is how it smells unlit. They are not the same measurement and one does not predict the other, plenty of candles smell wonderful in the jar and disappear once you light them.
Two different physical situations
- Cold throw is fragrance evaporating slowly from a solid wax surface at room temperature. It is the smell that sells a candle off a shelf, and it comes from a tiny surface area at low temperature.
- Hot throw is fragrance carried out of a pool of hot liquid wax. Far more surface, far more heat, far more volatility, and a completely different set of variables governing it.
Because the two situations have so little in common, a strong cold throw genuinely does not predict a strong hot throw. This catches people out constantly, and it is not a fault in the candle.
What controls hot throw
- The melt pool. The biggest single factor. Fragrance comes out of liquid wax, so a pool that reaches the container wall throws far more than one that does not. This makes hot throw largely a wick question.
- Fragrance load. How much oil is in there, measured against what the wax is rated to hold. Past that rating more oil does not help, it weeps out instead.
- Cure. A candle burned before the fragrance and wax have bound throws weakly, and people frequently diagnose this as a bad fragrance.
- The wax itself. Different waxes hold and release fragrance differently.
Diagnosing a candle that doesn't smell
Work through it in this order, because it goes from most to least likely:
- Strong cold throw, weak hot throw? Suspect the wick first. The fragrance is clearly in the candle, it is not getting into the air, which means the melt pool is too small and the wick is undersized.
- Weak both cold and hot? Suspect the load or the cure. Either not enough oil went in, or it has not had long enough to bind.
- Good at first, fades later? Normal to a degree as the candle burns down, but a sharp drop-off can mean the fragrance was not evenly dispersed through the wax when it was poured.
The counterintuitive bit: the most common fix for a candle that does not smell is not more fragrance. It is a bigger wick.
Good to know
Questions people actually ask
Why does my candle smell great in the jar but not when lit?
Almost always an undersized wick. The fragrance is in the wax, the melt pool is too small to release it into the room. Adding more fragrance will not fix this and can cause weeping.
How long does a candle need to cure before it throws properly?
It depends on the wax, and published figures vary a great deal. Soy generally benefits from noticeably longer than it takes to set solid. If in doubt, test-burn one from the same batch at intervals rather than trusting a single number.
Does a more expensive fragrance oil throw better?
Not reliably. Throw is dominated by the melt pool, the load and the cure. A premium oil in an under-wicked candle still will not fill a room.
Blend something that works lit
In a Candle Craft session you build a scent from the studio's fragrance library, with someone on hand who knows how a blend behaves in a melt pool.