In this article, we will briefly explore the colourful world of dyes and pigments that we can use in our cosmetic products. We’ll try to understand what is colour, what is the difference between dyes and pigments and I will give you some hints on what NOT to do when you try to formulate makeup products.
What is colour?
Have you ever wondered why do some materials appear blue, others red and others white?
It’s all a matter of absorption and reflection. Visible light is made of a mixture of different wavelengths. Each material can absorb some of these wavelengths and reflect others: the wavelengths that are reflected and reach our eye determine the colour we attribute to the material. A material that does not absorb nor reflect light is seen as transparent. An object that absorbs all wavelengths and does not reflect any is perceived as black, whereas materials that reflect all wavelengths is seen as white.
The visible light is just a portion of the light spectrum: it’s the part that our eye can detect. It goes from wavelengths of around 400 nm (violet-blue) to 700 nm (red).
So a dye that absorbs all wavelengths of the blue part will reflect the red part and we will see it as red, and viceversa (1-3).
Some colour theory
This is more art than chemistry and cosmetics, but if you’re here it probably means that you are interested in creating makeup products, and you might be interested in knowing how colours are related to each other (4).
If you take a look at the colour wheel, you can distinguish different characteristics of colours:
- Hue: the hue is the pure colour, the name we give to it. Hues are for example blue, red, yellow, green, etc.
- Value: the value gives information about the darkness or lightness of the hue. The addition of black or white to the hue changes the value.
- Intensity: it is related to the saturation of the hue and varies by addition of gray to the hue.
Furthermore, you can distinguish:
- Primary colours: red, blue, and yellow hue.
- Secondary colours: colours obtained by mixture of primaries (violet, green, orange)
- Complementary colours: each secondary colour has its complementary colour, that is, the primary colour that it does not contain. Violet (blue + red) and yellow are complementary colours; green (yellow + blue) and red are complementary colours.
- Intermediate colours: mixtures of a secondary colour with a primary colour.
- Warm colours: red, yellow, and orange
- Cool colours: blue, violet, and green.
Water soluble dyes
Water-soluble dyes are typically organic dyes and they are indicated with FD&C or D&C in their commercial name (food, drug, and cosmetics-approved or drugs and cosmetics-approved, respectively). Their INCI name is typically CI (colour index) followed by a number.
The use of such dyes in cosmetic products is strictly regulated. You can find a list of allowed dyes (in EU) at reference (5). Water-soluble dyes can be synthetic or natural. You can find examples of naturally derived dyes at reference (6).
Use in DIY cosmetics. In DIY cosmetics you can use water-soluble dyes (or food dyes) to give a touch of colour to your water-based lotions (O/W emulsions and gels).
If the dye is resistant to alkaline conditions, you can use them also to dye soaps.
You cannot use them in makeup products: water-soluble dyes tend to leave stains on the skin, they are neither soluble nor dispersible in lipsticks and oil-based makeup products, and they would anyway tend to migrate, yielding awful performances.
To give a touch of colour to a lotion, it is sufficient to use just a little drop of dye. If the dye is very concentrated, you should dilute it first in water and then use a drop of this dilution. Be very careful when colouring your creams: you should just give a shade of colour without exceeding, otherwise the cream will stain your skin.
In makeup products you should use powder pigments, that are insoluble in water and in oil. Most of them are inorganic. We can distinguish makeup pigments into fillers, pigments and whites (7).
Filler powders are inorganic powders that we can add to our makeup products to add volume to the whole product and to achieve or improve flow and touch features of the product.
Talc: magnesium hydroxide and silicate, widely used in makeup as filler and for its ability to reduce friction and improve flowability and spreadability of the product.
Silica: silicon dioxide, makes cosmetics smoother and more transparent.
Iron oxides: red, yellow, and black oxides. They are sold as pure or diluted with kaolin (the “Ocres” by Aroma Zones).
Ultramarine: blue-violet pigment made of aluminum, silicon and sulfur. Very bright and cool tones.
Chromium hydroxide: green oxide. Very bright, similarly to iron oxide, but not suitable for use in lipcare products.
Carbon black: used as black pigment and in skincare products. Less intense than black iron oxide.
Titanium dioxide: it has the highest refractive index, which makes it highly concealing and opaque. It is added to almost all makeup pigment mixtures to allow the colour to be “seen”. The titanium dioxide normally used in decorative cosmetics has particle size around 200 nm.
Zinc oxide: another white pigment, often used together with titanium dioxide but has lower refractive index (it is less concealing and less opaque). Zinc oxide used as decorative pigment has particle size range of 300-500 nm.
How NOT to formulate makeup products
- Don’t use water-soluble dyes, like food dyes
- Don’t use pigments that are not safe for lipcare products
- Don’t use water-soluble or food dyes
- Don’t use crayola markers, colored pencils, graphite, anything that is meant for DRAWING AND ART and not for makeup. You’re not a canvas. You’re a person.
- Don’t use water soluble or food dyes
- Don’t use anything that is not meant for makeup (don’t use drawing and art supplies)
- Don’t use indigo powder or henna mixed with whatever components (I’ve seen someone making mascara with vaseline and indigo powder: NO)
- Don’t use whatever oil mixed with whatever pigment: mascara is a very complicated product. It is typically an EMULSION in which makeup pigments (like black iron oxide) are dispersed. It’s NOT sufficient to mix an oil or vaseline to whatever black thing.
- Eyes are a delicate part of our body. I don’t recommend formulating mascara at home in the first place. This time, it’s safer to buy one.
(1) Visible spectrum, Wikipedia page (English) https://en.wikipedia.org/wiki/Visible_spectrum
(2) The visible light spectrum, ThoughtCo https://www.thoughtco.com/the-visible-light-spectrum-2699036
(3) Energy bands, Britannica https://www.britannica.com/science/color/Energy-bands
(4) Project Colours, Vobs http://www2.vobs.at/ball-online/Topics/COLOURS/Project_colours.htm
(5) List of colorants allowed in cosmetic products , EU Open Data Portal https://data.europa.eu/euodp/en/data/dataset/cosing-list-of-colorants-allowed-in-cosmetic-products
(6) Natural colourants in skincare, Formula Botanica https://formulabotanica.com/38-natural-colourants-skincare/
(7) Nonomura (2017), Powders and Inorganic Materials. In Cosmetic Science and Technology: Theoretical Principles and Applications (eds. Sakamoto, Lochhead, Maibach, and Yamashita)