Testing a Formula for User Abuse

One of the tests I developed for a final fragrance is called "user abuse" or UA. The goal of the test is to determine if a fragrance exhibits any issues resulting from multiple applications during a short time period. During this test, I'll respray/reapply the juice on a skin location 5-10 minutes after an initial heavy spray. This commonly may not be done by a user, but in case it is, I don't want any issues to develop.

Some typical outcomes of the UA test are:

Soapy/Laundry detergent: this can occur when florals containing aldehydes/linalool are involved, as they can converge to soapy when used too much. The second application launches the concentration of florals into the extreme zone, resulting in a soapy, laundry detergent, or a luxury hotel soap scent. Too much "rose" or phenyl ethyl acetate (PEA) can cause this.

Totally flat/no scent ("linalool flood"): This is easily caused by a combination of too much linalool from multiple materials. The second application results in a flood of too much linalool. During the flood, linalool forms a waxy matrix layer and prevents volatiles from escaping. What contains linalool? A lot of top-middle materials.

Slow diffusion ("musk overload"): This can be caused by hydrogen bonds between hydroxyl –OH groups of top-middle notes (linalool, geraniol, citronellol, PEA) or –C=O groups (aldehydes, ketones, esters) and the carbonyl oxygens of macrocyclic musks, or polar regions of nitromusks/polycyclic musks. Other complexes that can be formed are dipole-dipole interactions between polar carbonyls in esters and aldehydes and polar faces of musk molecules, and Van der Waals/London dispersion with ethylene brassylate. Musks also penetrate deeper into the skin because of their lower volatility (lower evaporation rate, oil-soluble), so if they form complexes with top-middle materials, they'll merely become trapped, resulting in slow diffusion.

Rubber/Railroad ties/Shoe Repair Shop ("phenolic hell") : I call this "phenolic hell," which can easily be caused by an excess amount of phenols in the final fragrance. Creosote (railroad tie smell) has a lot of phenols. I typically run into this when creating leather accords, especially from isobutyl quinone.

The exclusion criteria for preventing failure of the UA test are:

-Are there too many florals present?

-Is there too much total linalool present?

-Is there too much musk used?

-What is the total amount of phenol?

Sometimes I won't use the UA test on a fragrance. For example, for a modern, high-sillage fragrance for which the entry into a meeting, room, club, event, needs to be very pronounced, i.e., "here I am," I don't assume the user will use multiple applications early on. There's usually a greater risk of the above issues occurring when developing chypres/fougeres, which [to me] require higher fidelity between materials.