How to write a perfume formula in percentages

A published formula rarely says which percentage it means, and there are three. Parts are any unit you like as long as every line uses the same one. Percent of the concentrate is each line over the total of the aromatic lines. Percent of the finished product is that share again, multiplied by the strength the concentrate is worn at. A line can be ten parts, five percent of the concentrate and one percent of the product, all at once, and all three are correct.

Start in parts, finish in mass

Parts are the honest way to compose, because a formula in parts does not care how big the trial is. When you weigh it, parts become grams at whatever scale you choose, and the percentage of the concentrate is each line's grams over the total. Write the formula in parts, weigh in grams, and let the percentages be computed from the grams rather than written by hand; a hand-written percentage column is the one that stops summing to a hundred.

Say what strength it is worn at

The concentrate is not the perfume. A concentrate worn at fifteen percent in alcohol has every line at fifteen percent of its concentrate share, and that is the number safety limits and impressions are about. A formula without a stated strength is half a formula. Write the strength beside it, and keep the two percentages apart: concentrate for composing, finished product for compliance and for comparing with somebody else's formula.

A diluted line is not what it says

The commonest error in a written formula is a line weighed from a dilution and written as if it were the material. Two grams of a ten percent dilution is a fifth of a gram of the material and 1.8 grams of solvent. If the formula says two grams, everyone who remakes it from a neat bottle makes something ten times stronger on that line. Write the dilution beside the line, or write the corrected aromatic mass; never leave a reader to guess. The formula calculator takes lines at the strength they were weighed from and gives the corrected share of each.

Solvent is a line too

Alcohol, or whatever carries the concentrate, belongs in the written formula as its own line, because the strength is only true if the solvent is counted. Water and fixatives added at the bottling stage go in the same place. A formula that stops at the aromatic lines is a concentrate recipe, and it should say so.

What the bench does with all this

PerfuMate writes a formula in grams and shows the concentrate percentage and the finished product percentage side by side, with each line corrected for the dilution it was weighed from and the solvent shown as a line. Change one figure and every percentage recomputes, so the columns cannot disagree with each other. Open the bench and write one; the arithmetic is done as you type.