Database/Hair Dyeing/Acid Blue 9 Aluminum Lake
Mostly natural · ISO 16128

Is Acid Blue 9 Aluminum Lake natural?

Mostly. Mostly mineral alumina carrying a synthetic dye; the alumina substrate makes up most of the mass.

INCI nameAcid Blue 9 Aluminum Lake
CAS68921-42-6
FunctionHair Dyeing
FeedstockBrilliant blue FCF is synthesised from petrochemical 2-sulfobenzaldehyde…

How we scored it

Lake: the dye is laid on an alumina (aluminium hydroxide) substrate. Dye content varies by grade (often 10-40%); taken as 25% dye on 75% alumina, the same assumption as the other lakes. Alumina is mineral. Dye part, brilliant blue aluminium salt: three sulfonates and aluminium 258 of 765 Da, natural fraction 0.34. 0.75 + 0.25 x 0.34 = 0.83.
What counts. ISO 16128-2 scores the atoms that remain in the final ingredient. Reagents, solvents, catalysts and protecting groups used during manufacture leave no mass behind and are not counted.

Where it comes from

Brilliant blue FCF is synthesised from petrochemical 2-sulfobenzaldehyde and N-ethyl-N-(3-sulfobenzyl)aniline, oxidised and precipitated on alumina hydrate with an aluminium salt. No natural-origin route exists, and the mineral alumina substrate is excluded because its proportion is not specified.

In plain English

A blue colourant of the lake type: a water-soluble synthetic dye (brilliant blue) fixed onto aluminium hydroxide so it stays insoluble. It is listed for hair dyeing. The dye itself is made from petrochemical aromatic chemicals.

CosIng definition: Acid Blue 9 Aluminum Lake is classed chemically as a triphenylmethane colour. It conforms to the formula:

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References

  1. 1ISO 16128-1:2016 and ISO 16128-2:2017 — Guidelines on technical definitions and criteria for natural and organic cosmetic ingredients and products. ISO, Geneva.
  2. 2ACID BLUE 9 ALUMINUM LAKE. CosIng — European Commission cosmetic ingredient database. ec.europa.eu/cosing ↗
  3. 3ACID BLUE 9 ALUMINUM LAKE. CosIng u2014 European Commission database for information on cosmetic substances and ingredients. https://ec.europa.eu/growth/tools-databases/cosing/search?search=ACID%20BLUE%209%20ALUMINUM%20LAKE