Perfume fixation

We regularly receive questions about fixation of fragrances, not only with perfumes, but also with soap and other products. Apparently, there is quite some confusion about this, hence this article.

Before we get clear on what fixation is, we need to explain how fragrance ‘works’ and also how evaporation works.

How scent works

Smells work with your nose. In your nose there is a piece of tissue, the olfactory epithelium, that is sensitive to the action of certain chemical substances, the odorants. In the olfactory epithelium there are several hundred types of odour receptors, a kind of odour sensor, each sensitive in a different way. When an odour substance hits these sensors, the odour receptor sends a signal to the brain. From all these signals the brain makes an odour impression. In fact, the smell only exists in your head.

In order for the odourant to reach the right place in your nose, it has to come in the form of a gas, or at least very finely divided. Most fragrances therefore evaporate quite easily. Substances that do not evaporate easily usually have no or very little scent.

Some fragrances evaporate very quickly and easily. You put down a drop of such a fragrance and an hour later there is nothing left. You can no longer smell the fragrance, everything has already evaporated and no new fragrance will enter your nose. Other fragrances take a very long time to evaporate, maybe months later the drop is still there.

With terms like tenacity and volatility we try to get a grip on the mechanism behind evaporation.

Tenacity

Tenacity means how well the fragrance adheres (to the applied perfume, soap, wax, scented product). If the tenacity is high, the fragrance will remain intact for a long time. With a perfume, it is nice that you can smell the fragrance immediately after application, but also after an hour or a few hours. On the other hand, it is also nice that it is all gone after a shower.

Depending on the product, we want more or less tenacity. Take washing-up liquid. When you open the bottle and make a lather, of course it has to smell fresh and citrusy. But the plates and glasses shouldn’t smell of lemon for too long. After all, we don’t want the kale stew to smell of lemon, or the wine. So the tenacity should not be too high.

Washed clothes have to stay smelling nice after a couple of weeks in the closet, so fragrances for washing powder should have a high tenacity.

Soap is another story, a bar of soap has to be able to give off a pleasant scent for years. Although in theory soap is meant to get clean, it is the smell, colour and shape that are important for buying and for appreciation. But: your skin may smell of the soap after washing, but not hours later. Therefore, the tenacity should be high on the one hand, but not too high on the other.

Volatility

Fragrance raw materials are solid or liquid, to be smelled they have to evaporate. How easily does that happen? If it is easy, then the volatility is high. In the case of a perfume, the most volatile odourants can be smelled immediately after application; they evaporate easily. After a while, the most volatile fragrances will have evaporated.

When making a perfume, you take this into account by using both easily and less easily evaporating substances. This creates the olfactory pyramid: top notes are mainly the smells of easily evaporated substances, base notes of slowly evaporating substances and the heart notes are in between.

For soap, candles and the like, you mainly use slowly evaporating substances. A substance that is too volatile would have largely evaporated before the candle is even sold.

Fixation

For a certain fragrance application you want to have a certain tenacity. The best way to achieve this is to use fragrance materials with the desired tenacity. For detergents a low tenacity and high volatility. For scented candles a higher tenacity and low volatility. For a perfume one chooses substances with a high as well as a low tenacity.

A modern perfumer will always take these factors into account. If the tenacity of the product is not right (too much or too little), she will adjust the fragrance composition until it is right.

In the past, perfumes and other fragrance products were fixateded to get the tenacity right. Occasionally this will work a bit, but in many cases it is a pointless procedure.

The theory of fixing is that you add a certain amount of substances with low volatility. This would make the whole mixture evaporate less and thus increase the tenacity of the perfume. Typical fixatives were the tinctures of animal substances (musk, civet and ambergris), resins and resinoids. An odourless substance such as DEP was also used.

More modern mixtures of fixatives are generally mixtures of low-tenacity fragrance materials with a not too pronounced odour, which suit almost every perfume. Think of jonons and musks.

Disadvantages

Most importantly, fixation only helps a little, if at all. It can round out a good perfume, but it can’t save a poorly composed one as a rule.

Even if you use odourless or relatively neutral fixatives, the smell of your perfume will be different after fixation. Better if you’re lucky, but probably worse. Certain aspects of the original fragrance will be enhanced, others weakened.

For many types of product, fixation is a hopeless task. There is no product that makes lemon oil suitable as a fragrance for soap or candles.

The advice is therefore: make a good product to start with. Do not fix it afterwards with a fixative.

Traditional fixation method of perfumes

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Finally, a word about the traditional fixation method for perfumes, which you might want to try if you want to make a perfume in old-fashioned style. This fixation consists of using a fixative when diluting the fragrance composition into a perfume. Traditionally, this is often musk tincture*, civet tincture or ambergris tincture*. The recipe for blending a perfume is then, for example, as follows:

  • 200 g of perfume composition
  • 40 ml civet tincture 3%
  • Fill up to 1 litre with 90% alcohol
  • .

The perfume must then mature for several months.

You could do something similar with Muscenon (3% in alcohol), Fixateur 505 (Fir) (5% in alcohol) or Civette Synth (Fir) (3% in alcohol).

* Trade in real musk and real ambergris is prohibited in the Netherlands and many other countries. The animals from which these substances are extracted are threatened with extinction and therefore protected almost everywhere by the Cites convention. In countries where the CITES convention is not valid or is interpreted differently, these substances may be on the market. If you see it for sale online: remember that both substances have a centuries-old history of forgery, counterfeiting and adulteration. Certainly musk products are generally not made from real musk.