Fragrance without flame: how wax and diffusers work
A home fragrance without a flame and without electricity does not sound very technical. In fact there are two different physical processes behind it, and once you know them, you immediately understand why some fragrances are gone after three days and others are still there after months.
One is evaporation from solid wax, the other is capillary action in a wooden reed. Both work slowly, and that is their real advantage over anything that sprays.
Why a spray is no good
A fragrance that fills the whole room immediately consists mostly of alcohol. It evaporates in minutes and takes the fragrance substances with it. What remains is a short, very intense cloud and then nothing.
Both methods discussed here do the opposite. They release a small amount continuously. The room never smells strong, but the scent is constant – and that is the difference between a fragrance you notice and one that belongs to the room.
Wax releases at room temperature
A scented wax needs neither a wick nor a heat source. The wax binds the fragrance oil, and at room temperature a tiny part of it constantly comes away from the surface and goes into the air.
Soy wax is particularly suitable for this. It typically takes up six to ten per cent fragrance oil and holds the fragrance back better than paraffin – it releases it more slowly and more evenly. That is exactly what is intended: a bar that is finished in two weeks contained too much fragrance oil.
The release depends on temperature. In a warm spot it rises considerably, in a cool room it falls. Put a wax bar next to the radiator and you get more fragrance for less time. That is neither a recommendation nor a prohibition; it is simply how you control it.
The second control is the surface. A bar lying flat releases more than one standing on its edge – what counts is the area in contact with air, not the weight.
The diffuser works by capillary action
A rattan reed looks like a solid piece of wood and is not one. It is a bundle of microscopically fine longitudinal channels, each of which works like a very thin straw.
When such a reed stands in oil, the adhesive force between the liquid and the channel wall is greater than the cohesion of the liquid itself. As a result, the oil is drawn into the channels and transported upwards – against gravity, without anything supplying energy for it.
At the top, where the reed stands freely in the air, the oil evaporates and releases the fragrance substances. At the bottom, liquid immediately moves up to replace it. This creates a cycle that runs by itself as long as there is oil in the vessel.
To go with this article
Why you turn the reeds over
Over time the effect diminishes, and there is a mechanical reason for this: at the top end the oil has evaporated, leaving behind the heavier components and dust, which clog the channels.
If you turn the reeds over, the spent tip goes down into the oil and the fresh, open end comes to the top. The cycle starts again. Every few days is enough.
The number of reeds can also be used to adjust the intensity. More reeds means more evaporating surface, so more fragrance and a shorter lifetime. In a small room a few are enough.
The one mistake that causes damage
With sets in which fragrance oil is put onto stones or into a bowl, there is a rule that is rarely stated: the oil goes onto the stones, not into the bowl.
Fragrance oil that sits directly on glass leaves discolouration that stays. It is not dirt that could be washed off – the surface itself changes. The stones, by contrast, are porous, take up the oil and release it slowly again; that is exactly what they are there for.
Stones that no longer release well after a long time go into warm washing-up water for ten to fifteen minutes and are then left to dry. After that they take up oil again.
Where to place a fragrance in the room
Fragrance substances move with the air. A diffuser in a still corner works almost only there; a diffuser near a door or a draught spreads through the whole room – and is correspondingly empty sooner.
A sensible place is one where there is regular movement without a constant draught: next to a passageway, on a chest of drawers in the hallway, at a spot you pass anyway.
The windowsill in the sun is not a sensible place. Heat and UV accelerate both – the evaporation and the breakdown of the fragrance substances. The fragrance is then not only gone sooner, it also changes beforehand.
How long a fragrance lasts cannot be reliably stated in weeks. Room size, temperature, draught and the number of reeds shift it many times over.
Frequently asked questions
How does a scented wax work without a flame?
The wax binds fragrance oil and at room temperature constantly releases a small part of it into the air. The warmer the location, the more fragrance and the shorter the lifetime.
Why is soy wax widespread?
It typically takes up six to ten per cent fragrance oil and holds the fragrance back better than paraffin – it releases it more slowly and more evenly.
How does a reed diffuser work?
Through capillary action. A rattan reed is a bundle of fine longitudinal channels; the oil is drawn upwards in them and evaporates at the top end. At the bottom, liquid moves up to replace it, and the cycle runs by itself.
Why should you turn the reeds over?
Because the top ends clog with heavier residues and dust. Turning them over brings an open end to the top, and the release starts again. Every few days is enough.
Can fragrance oil go directly into a glass bowl?
No. Fragrance oil on glass leaves permanent discolouration that cannot be washed off. With stone sets the oil goes onto the stones, because they take it up and release it slowly again.
View all home fragrances in the shop
View all decoration in the shop
