Why Fir Smells Like Fir: Bornyl Acetate and Its Crowd
Ask anyone who knows a little about conifers what makes fir smell like fir, and the answer is bornyl acetate. It is a good answer, and only half the story.
Fir Needle Essential Oil
Our own Fir Needle Essential Oil, in sizes from 0.5 oz to bulk.
From $10.99
Shop Now →The compound everyone names
Bornyl acetate is the acetate ester of borneol, described as woody, pine, herbal, cedar, spicy and camphoraceous. Reference works cite Ullmann's encyclopedia in saying that needle oils of the pine family carry (-)-bornyl acetate as their main odoriferous component. That is a statement about smell, though, not about quantity, and published fir analyses differ widely on how much is actually in the bottle. A Siberian fir oil came in at 30.63%; a silver fir oil at just 4.2%. Douglas fir, which is not a true fir, ran higher still. "Fir" covers a lot of chemistry.
The air is not the bottle
The most interesting result we know of comes from Garzoli and colleagues, who sampled the air above a silver fir oil as well as the oil itself. In the liquid, bornyl acetate was 4.2%; in the vapour, 0.4%. Alpha-pinene rose from 30.8% to 51.3%, and camphene from 11.2% to 16.5%. Limonene went the other way, from 32.5% to 19.0%.
It makes sense once you line up boiling points. Alpha-pinene boils around 155 to 156 C, camphene at 159, limonene at 176 and bornyl acetate at 223 to 224. Lighter molecules reach your nose first, and heavier ones show up later and in smaller amounts. A closed vial at 60 C is not a living room, and this was a single oil, so we would not carry the numbers over. The direction is what is useful: the opening minutes of fir on a diffuser pad are bright and piney, and the deeper, sweeter woody notes follow. Our scent profile guide turns that into a way to smell the oil in stages.
The rest of the cast
- Alpha-pinene and beta-pinene are the most widespread terpenes in conifers and lead many fir analyses. Balsam fir, in one oil analysed by Pichette and colleagues, was led by beta-pinene (29.9%), delta-3-carene (19.6%) and alpha-pinene (14.6%).
- Camphene carries woody, herbal and fir-needle descriptors, and is a good example of why "fir" is itself a scent word in perfumery.
- Delta-3-carene is described as sweet and pungent, reminiscent of fir needles and damp woodland.
- Limonene is the familiar citrus compound in its common form. The less common mirror-image form is described as piny and turpentine-like, which is part of why fir oils can read as lightly citrus-edged.
Why freshness matters
Several of these molecules, among them alpha-pinene, carene and limonene, react with oxygen as an oil ages, and oxidised terpenes are a known source of skin reactions. The Tisserand Institute says oxidation products can raise the likelihood of an adverse skin reaction, and that heat, light and moisture speed the process. The practical advice is happily simple: buy fresh, cap tightly and store cool and dark, which we cover in our storage guide.
And our bottle?
We sell one fir needle oil, undiluted. The Certificate of Analysis we publish for one batch names Abies balsamea and gives density and refractive index, not a compound list, so we leave the percentages to the studies above. If you need a compound breakdown for your formula, ask us in writing through the contact page before ordering. Meanwhile the studies give you a feel for the family, and our GC/MS reading guide shows how to use one when you have it.
Fir's crisp scent is a team effort, with bornyl acetate as the sweet, lingering backbone and the pinenes as the bright first impression, and once you know that, every bottle gets more interesting to smell.
Fir Needle Essential Oil
Fir Needle Essential Oil from our own shop, in sizes from 0.5 oz to bulk.
From $10.99
Shop Now →