Hair dyes: types and functions

Maria Shilovskaya , independent expert in the field of chemistry for hairdressers, teacher at the S. Gevorkova School of Color.

Many people associate hair dye with the word “alkali” and this association is absolutely justified, since for most dyeing it is necessary to penetrate deep into the cortex (into the cortex) , past the cuticular layer. Alkaline components handle the function of “passing” into the hair. Therefore, out of the 5 types of dyes available today, 3 of them contain alkalis.

Anything that has a pH level between 7 and 14 is alkaline. The closer to the number 14, the stronger the alkalinity and damage to the hair structure. At pH 10+, the process of protein denaturation (destruction) starts to varying degrees, depending on the initial condition of the hair. It is always worth paying attention to this when choosing a certain type of dye for a client, since one of the differences between them is the different pH level.

What is alkali and what functions does it perform?

The alkali dissolves the protective lipid layer covering the skin and the root part of the hair and opens the cuticle, providing access to the cortex. The latter, in turn, swells under the influence of alkali, passages and “tunnels” appear in it, which enable other ingredients of the composition to penetrate deep into the hair. In other words, alkalis loosen the hair and the higher the pH, the more hair is loosened. If we talk about dyes containing oxidative pigments (i.e., those that need oxidation for color to appear), then in addition to the above functions, alkaline components activate the breakdown of hydrogen peroxide, which is found in the oxidizing agent. Hydrogen peroxide itself is responsible for the dispersion (dispersion) of natural pigment in the hair and for starting the color polymerization process.

Color polymerization is the formation of large colored developed molecules from small colorless color precursors.

Depending on the pH level, dyes can be divided into 4 groups:

Permanent or ammonia

The main alkali is Ammonium hydroxide (ammonium hydroxide) - ammonia or ammonia water, a liquid that breaks down into water and ammonia. Therefore, both Ammonium hydroxide and Ammonia can be found in permanent products.

The pH level ranges on average from 9 to 11 - the lower the pH, the darker the shade and vice versa.

The main task of permanents is to deliver the pigment as deep as possible into the cortex, since in most cases it is the depth of penetration of the pigment that affects the wearability of the color. For this reason, the pH of such dyes is maximally alkaline compared to other types. Permanent pigments require the presence of hydrogen peroxide, therefore they are always paired with an oxidizing agent.

For the tinting procedure, which is carried out after lightening, it is advisable not to use such dyes due to their high alkalinity. Careful “weathering” of the composition before tinting will not always lower the pH, since many special blonds, in addition to ammonia, also contain other alkalis that are unable to volatilize.

Semi-permanent or demi-permanent, ammonia-free

Instead of ammonia, this type of dye contains its derivative - ethanolamine Ethanolamine . Such dyes do not have a pronounced odor and contain a more gentle pH level (within 8-9). Initially, demi-permanents were created as a “healthier” alternative to classic coloring, so most of them contain a considerable amount of care and protection elements (proteine, oil, extract, amino acids, peptide, etc.).

Semi-permanents are designed for coloring tone-on-tone and several shades darker. Such products practically cannot cope with lightening. Almost always, pigments of this group are oxidative and require the presence of an oxidizing agent. Alternatively, such dyes are used for tinting after hot bleaching due to low alkalinity and the presence of care in the composition.

Semi-permanent or PPD (direct action pigments)

This type of dye is slightly alkaline (pH 7.5-8) and is capable of loosening only the upper cortex layers, slightly opening the scaly layer. But we should not forget that the higher the hygroscopicity (porosity) of the hair, the deeper the pigment will “fail”.

Alkalies most often contain either Ethanolamine (ethanolamine) or Sodium hydroxide (sodium hydroxide). Often alcohols such as Ethyl alcohol (Ethanol), Alcohol denat., Isopropyl alcohol, which act as conductors and transporters, come to the aid of alkalis. They “help” other components of the composition penetrate deeper into the hair.

Semipermanents contain an already developed small colored molecule, so they do not require the presence of an oxidizing agent. The composition of such dyes in most cases does not contain any maintenance and is limited only to water, alkalis, alcohols, pigment, fragrances and several structure formers that directly affect the consistency of the product.

What are they used for?

- Renewing color and giving it depth;

- Creating rich, bright shades on pre-bleached hair, carrying out preliminary pigmentation before tinting (it is especially important to use a yellow semi-permanent before tinting blonde in order to prevent color “failure” and prolong durability);

- Additional color saturation of “physical” dyes.

Minus : the lack of information in the composition about the “adequacy” of the pigment located inside - the crimson color of one brand will smoothly leave the hair after several times of shampooing, while the same shade of another brand will firmly “grab” into the cortex until the haircut.

You can “understand” the pigment only by testing a strand or thanks to reviews from colleagues.

Physical or toning

This group of dyes DOES NOT CONTAIN ALKALI and has a pH of 7 or lower. Their task is to work exclusively on the surface of the cuticular layer. Such “superficial” work is possible only on healthy hair with normal, reduced hygroscopicity and tightly closed scales. Otherwise, the dye molecules will still be able to at least partially “deepen” into the cortex layers, which will significantly increase the wearability time of such staining.

The molecules of physical dyes are large and colored, so they do not need contact with an oxidizing agent. They settle on the surface of the hair due to physical polarization - different charges of the hair and dye molecules are attracted to each other. A characteristic feature of this type of composition is the presence of a large number of caring components (proteine, oil, extract, amino acids, peptide, keratin, collagen, elastin, ceramide, etc.), moisturizers (glycerin, propylene glycol, sodium PCA, aloe barbadensis leaf juice, etc. ), as well as film-forming ingredients (dimethicone, dimethiconol, PEG, PVP and others).

What are physical dyes used for?

Physical dyes are used to refresh color, temporarily brighten hair, and neutralize unwanted yellow or orange highlights between blonde hair coloring sessions. After using such dyes, the hair is filled with shine, becomes smooth, silky and more manageable.