The Chemistry of Hair Dye

What on earth would we do if hair dye was taken away from us? It is a wondrous substance that helps to cover our grey hair and keep us looking younger, or it gives us that extra, all important boost to our appearance. Basically, instead of putting up with what good old Mother Nature gave to us, it actually gives us certain autonomy about our appearance, which then goes hand in hand with developing our personalities and the way that we interact with others.

None of us give much thought to how hair dye is actually produced. All I need to know is that it comes out of a bottle, that I need to make a thorough job of covering my roots, and I definitely mustn’t get any on the floor coverings or furniture. Aside from that, and the fleeting thought that it smells of cat pee when I am using it, I have never really given much thought to the chemical makeup of hair dye.

Did you know that hair dye has been around for thousands of years? Early records show that the ancient Egyptians, Greeks, Hebrews, Persians, Chinese, and early Hindu peoples all mention using hair colourings in one form or another.

Up until the 19th century, the only dyes available were those that had been prepared from a natural source, and by combining various plant extracts, it was possible to create a fairly extensive range of colors. Indigo, although commonly used as a fabric dye, could be mixed with henna to give varying shades of brown for example.

Other substances that have been used for dyeing hair or wigs are rock alum, black sulfur, and honey. Lead, quicklime, and salt, or silver nitrate in rose water. Another early method of coloring hair was to apply powders made up of wheat starch, powder of paris or potato starch combined with chalk, burnt alabaster, and the colorants, burnt sienna or umber.

The late nineteenth century saw the introduction of Hydrogen peroxide at the Paris Exposition as an efficient hair lightener and thus begun the experimentation of chemical compounds to produce a synthetic dye. The first chemical compound developed was pyrogallol, and from 1845, pyrogallol (in combination with henna) was used to dye hair brown.

The 1880s saw the introduction of amino dyes of which p-phenylenediamine was the earliest. Before being applied to the hair it had to be mixed with caustic soda, sodium carbonate, or ammonia. Hydrogen peroxide was then applied, which then brought out the color.

Clairol were the makers to pioneer the first one-step hair dye in 1950. This made the process of dyeing hair so much easier and with a sophisticated chemical compound it meant that the time-consuming shampoo and pre-lightening steps could be eliminated from the process. Within a short space of time, women in the U.S. quickly realized that hair dye had developed into an easy to use product and by 1973 over 50% of women were taking advantage of this wonder product.

But what do our modern hair dyes contain now? There is not a doubt that it is a complex mix of ingredients, with each manufacturer differing in formula to retain an element of uniqueness.

Hair dyes generally contain dyes, modifiers, antioxidants, alkalizers, soaps, ammonia, wetting agents, and a plethora of different fragrance, and a mixture of other compounds used to impart different qualities to hair depending on hair type, color and texture. The chemicals are normally amino compounds, and you can recognize them by names such as 4-amino-2-hydroxytoluene and m-Aminophenol. Metal oxides, can also be added as pigment.

Resorcinol is a commonly used modifier, used to bring out the tone of color or set the dye. The dye is prevented from oxidizing with air by using an antioxidant such as sodium sulfite. Dyes work most efficiently in an alkaline composition so alkalizers (such as ammonium hydroxide) are added to the dye to change its PH formula

Added to these basic chemicals, will be a variety of chemicals to give a certain dye solution certain qualities will be suitable for different hair types and provide different application experiences.

Hydrogen peroxide is usually added to the product in a separate container and used as a developer.

There are various types of hair dyes on the market. These are temporary hair colors and Semipermanent dyes, which penetrate into the hair shaft, but wash out of the hair after five to ten shampoos.

A dye such as Grecian Formula 16 works by penetrating the cuticle and the Pb2+ ions react with sulfur atoms in the proteins to form lead sulfide (PbS), this give the effect of looking dark in color. This is a gradual dye that works by being applied on a regular basis to “build” up the color of the hair.

So the next time you reach for that bottle of dye or sit patiently in the hairdressing salon, as the smells of the chemicals waft around your nose you can reflect on the long journey that those hair dyes have actually been on, beginning with the base, natural and primitive ingredients of our ancient world through to the first tentative experimentation with permanent color to the sophisticated and easy to apply dyes of the modern world.

What a boring world it would be without them.