Louching Explained for the Student Perfumer - Anya's Garden Basic Perfumery Course - Module 6

Louching illustrated from http://en.wikipedia.org/wiki/Absinthe Pernod is a green liquor that turns milky white when water is added.  A lovely step-by-step illustration of louching.

In Module 6 of my basic perfumery course's textbook, I introduce the student to the sometimes scary time when your dilution or blend louches. The textbook is almost encyclopedic in breadth and depth, because my beginner students are encouraged to hold themselves in the highest regard, and to that end, be able to converse with professional perfumers, even though they have not achieved that status yet.  Knowing the language and definitons of perfumery is paramount to a great education.

Louching – a Blending Phenomenon

Something that you need to know about before you begin any serious work on your blends is louching.  This is a phenomenon that you are likely to experience when you are finessing your perfume and you add water to it in order to increase diffusivity.  The word louching describes the effect when a perfume (or alcohol, as in the case of adding water to Absinthe liquor) becomes “milky” or “hazy” in appearance.  This happens because when the water ratio reaches a certain level, the alcohol can no longer hold the oils in solution, and the ingredients form a micro-emulsion of oil and water.  The cloudy appearance is cause by the light refraction from the microparticles of oils in the blend.  

When a blend louches, sometimes merely allowing the perfume to sit in a cool atmosphere, undisturbed for a period of time, will allow the oils to go back into solution with the alcohol; but often it will not.  If the oils do not return into solution with the alcohol, then you can discard the blend (add it to your Millefleurs botte) and rework the formula with less water in it.  You can experiment with the water, adding it drop by drop, counting each one, until the blend begins to louche again, and then reduce the number of drops of water in your final formula. It’s best to be weighing your work as you go so that you will know the weight of the water that you are adding to your formula.

---------

Ernest Guenther discusses the louching factor, explaining if you add too much alcohol to ylang ylang, it will get milky.  This often occurs when students make their 10% dilution, and all it takes is a little time, maybe overnight, and the dilution clears.

As a student moves further along with blending, and louching occurs, often a sit in the freezer overnigh will clear the blend.  Playing around with ratios and having patience are important for the perfumery student.

http://PerfumeClasses.com