How do perfumers choose between alcohol or oil format?

Someone suggested I do a blog post to explain from the perfumer’s point of view how the decision is made whether to create a perfume in oil or alcohol form.  I thought it was a great idea because I receive questions about this issue quite frequently.  Why does a perfumer pick one base or the other?  Can any scent be made in either form?  I’ll try to answer some of these common questions.

What reasons might a perfumer have to create one or more scents in an oil base?

• Some perfumers like the way oil scents stay closer to the skin and last a bit longer, especially when made at parfum concentration.
• Some natural ingredients don’t mix well in alcohol, causing separation or settling out of material.
• Some perfumers don’t want to deal with the expenses, regulations, and shipping fees on alcohol.  (In the US, you need to purchase an expensive federal permit if you want to buy more than 5 gallons of specially denatured alcohol per year.  You can buy more than 5 gallons of undenatured alcohol, but you must pay a tax on it.  Shipping for alcohol is expensive too.)
• Some perfumers and customers like having the option of an oil base if they have skin issues with alcohol or if they’re looking for an all-natural product (though some natural perfumers use grape alcohol).

What reasons might a perfumer have to create one or more scents in an alcohol base?

• Some perfumers like the sillage that alcohol offers and/or the way alcohol perfume dries faster on the skin. 
• Some perfumers want to offer spray bottles because that format is popular.
• Many perfumers appreciate the way alcohol opens up a scent and really helps the fragrance bloom.
• Some ingredients only mix in alcohol and won’t do well in an oil base, causing separation or settling out of material. 

Some perfumers like to choose the base specifically for each scent, depending on what seems most appropriate for the scent.  And some perfumers prefer not to offer the same scent in both formats because that makes compounding more involved.

Many ingredients are easier to use if you pre-dilute them before incorporating them into perfume.  For example, many solids and resins need to be warmed and blended with alcohol (and possibly filtered to remove residue) before use.  Some of these substances can be thinned much more easily in alcohol than in oil bases.  Even when an ingredient can be incorporated into an oil base as well as in alcohol, that means keeping stock of the pre-diluted ingredient in two different forms.  Perfumers have so many bottles of things already, keeping two sets of ingredients for oil versus edp does complicate matters.  Some people avoid that issue by diluting resins in solvents that can be used in either oil or alcohol base, but others prefer to use alcohol as the solvent to tightly control and minimize the final percentage of common solvents like triethyl citrate and dipropylene glycol.  Some of these things are fine at small concentrations and can even add fixation, but if you add too much they will over-fix and damp down your fragrance.

The same issues apply to lotions as to oil bases because lotions are basically an oil base combined with a water phase by an emulsifier (there’s no alcohol).  To do a fragrance in lotion I have to keep a separate alcohol-free fragrance concentrate, and that’s only possible for scents that don’t require an ingredient that needs pre-dilution in alcohol.

I currently offer three scents from the perfume list in both oil and edp form: Opal, Egyptian Musk, and Velvet Rose.  I like to offer the musks in oil because many people like musk oil roll-ons.  I formulated Velvet Rose specifically with lotion in mind as a goal; I really wanted to have a rose lotion so I made sure I didn’t put anything into Velvet Rose that was incompatible with oil bases.   I originally did more oil scents but I’ve gradually shifted more toward alcohol because I like the way the fragrances mature over time and bloom in the alcohol base and I have enough to keep me very busy already without keeping multiple forms of fragrance concentrate for each scent.  (Also, I was originally drawn to oils since I am a dabber rather than a sprayer, but I later decided my favorite approach was to use alcohol parfum and dab it.)

Still, I’d like to add a few more of my scents to the lotion list after I deal with a labdanum issue.  I have one beautiful labdanum resin that works well in alcohol and I’ve used it in all my scents that contain labdanum.  I recently found a labdanum resin that can be used in either alcohol or oil and is close enough in smell to substitute in the oil and lotion versions of my scents.  When I have time I will reformulate a few scents for lotion with that new labdanum (I’ll keep the alcohol versions the same and just develop a slightly modified formula for the lotion versions).

Bath and body etailers who purchase ready-made fragrance oils in common solvent bases can easily just mix those fragrance oils into either oil or edp base, as well as into bases for soaps, lotions, etc.  But perfumers who compound their own blends from scratch using raw aroma chemicals and natural ingredients have lots more to think about when choosing bases for their fragrance concentrates.  Hope this has answered some questions about that process!  The answers to this question of oil vs alcohol will vary from perfumer to perfumer, but this should explain at least some of the issues involved.