Fixatives for Natural Fragrances

Hello.

Confession time, I am NOT a perfumer.

Here I am talking as a cosmetic chemist who has a couple of years of direct experience of working in a fragrance factory plus many more years working alongside perfumers but not AS a perfumer.

Now I’ll go on.

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Many people ask me how they can make their essential oil perfumes last longer, a legitimate request given that most essential oil perfumes don’t last that long at all when compared to your typical store-bought fragrance brands.  Some people even ask for fixatives, maybe with the idea that there are certain chemicals out there (fingers crossed that they are natural) that can magically turn a fleeting essential oil blend into something that lasts all day.  I want to address this from my perspective and knowledge base here.

Fixative.

First off it is important to note that fixative materials that may or may not have or impart an aroma of their own to a blend. Indeed, the most important feature of a fixative is that it reduces the volatility of the fragrance blend which, in turn, helps it to last longer.

Fixatives may make up a small or a large percentage of the overall perfume blend depending on the technology employed and the type of fragrance being created.

A few common examples of these non-smelly fixatives are:

Glucam P 20

Isopropyl Palmitate

Diethyl Pthalate (was very common once but now less so).

Glycerin (not that effective but sometimes useful depending on the application)

Benzyl Benzoate (weak odour, quite balsamic)

PVP

Hydroxyethyl Cellulose

Examples of fixatives that are smelly are:

Fixolide

Vanillin

Cinnamic Alcohol

Benzophenone

Musk Ketone

Fixative 505

Peru Balsam

Benzoin Resin

Tonka Bean

Vanilla

Sandalwood

Amyris Oil

Copaiba Oil

The trouble with trying to stick to essential oil and resins only to make perfumes is that often the fixative aroma elements are strongly smelly by themselves and, potentially very expensive.  The smell of the fixatives (such as Sandalwood or Vanilla) isn’t so much of a problem if you like and want the smell but it is an issue if you don’t.  This can make the exercise of making natural, essential oil derived perfumes restricting (although it is still possible to make some lovely natural aroma blends of course).

People often ask me for fixatives as an after-thought once they have trialled their essential oil blends and found them wanting.  This is probably not the best way to tackle the longevity problem given that natural fixatives have an aroma as inevitably increasing the aromas shelf life ends up requiring a complete re-formulation of the perfume.  So, my tip is to formulate for longjevity from the beginning.

Smell longjevity vs odour intensity.

Another misconception is that if a fragrance lasts longer it will smell stronger.  While there is some logic and truth to that it isn’t completely accurate.  Many essential oils have quite low fragrance strengths when compared to synthetics.  We will look at that here using Sweet Orange Oil as an example:

Natural Sweet orange essential oil has only an odour impact score of 110 (I’m not sure of the units of this so we’ll use it proportionately) and a longevity of 8 hours.

Compare that to a synthetic Orange fixative which has an odour impact score of 250 and a longevity of 60 hours.

We could then compare that to a synthetic blend of orange mid notes.   These may be used to enhance a citrus aroma and make it richer on impact rather than longer lasting.  Here we see an impact score of 83 and a odour life of 7.9 hours so less than we get for sweet orange as a whole.

However, we could also look at an Aldehyde C-10 Decanal This has an orange peel-like waxiness that gives an impact of 500 but a longevity of only 10 hours.

Looking at the four options for Orange-inspired fragrances above you can see that intensity and longevity can be played with to a much greater degree with these synthetic (or isolate) chemical blends vs the essential oil and that as such, a wider range of outcomes is available.

However, most people making natural perfumes don’t want to use these chemicals however they are made and yes, some can be isolated from natural sources, others are made from plant derived starting materials which then undergo chemical reactions and a few are purely synthetic.

So what can the natural perfumer do?

A) Consider the base note as part of the formula rather than something added to increase the life of an existing formula.  The base note may become a prominent feature in your blend but that’s inevitable when using natural materials, work to make it a seamless part of the blend rather than a functional add-on.

B ) Accept that it is likely impossible to create all-natural, whole material perfumes that last as long and have as high an intensity as synthetics.

C) Accept the price constraints of formulating with naturals.

On top of that natural fragrance creators can give themselves another helping hand by managing the oxidative stability of their blends.  Again, because of the natural ingredient philosophy, the choice in ingredients that can help slow down oxidation is less than for synthetic perfumers but there are some things that can help. Natural Vitamin E isomer blends are probably the best bet as they are less smelly than rosemary antioxidant and, in most cases more effective.   Even with antioxidants some fragrances, especially citrus based, will oxidise over time and that could lead to some notes flattening out and the overall blend colour changing.

The bottom line here is that natural perfumery is different and is limited but it is also beautiful, precious and fleeting in its beauty so maybe we should all stop trying to make it something it is not and just accept it’s here for a good time not a long time.

If you are interesting in aroma chemistry this resource is quite useful.

Amanda