Covering Grey Hair
Covering grey hair typically involves hair colouring with either hair dyes or progressive hair colorants. Women dye their hair for a variety of reasons. When it comes to hiding their white hair, they usually prefer to cover all their grey and, therefore, colouring their grey hair is in principle no different from a routine hair dyeing procedure, when both white and pigmented hair is dyed. Very few men colour their hair for reasons other than covering their grey. Since, in many cultures, for a man to dye his hair is not considered appropriate, most gentlemen wish to do it discretely and unnoticeably. This is where progressive grey hair colorants come in useful.
When it comes to hair dyes there are several types of them, differing mainly in the durability of their effect. The durability is related to the ability of the colour to penetrate inside the hair shaft. The hair shaft consists of two and sometimes three layers. The outer layer is called the cuticle and it is made of flattened cells that overlap like the tiles on a terra-cotta roof. The cuticle protects the inside of the hair shaft from damage. The layer beneath the cuticle is called the cortex and it is made up of long proteins that twist like the curly cord on a telephone. It is this layer that harbours the pigment that gives colour to your hair. In the centre of some hairs is the medulla, a soft, spongy mass of tissue. Coarse hair generally has this layer, while fine hair usually does not. Hence, referring to the above, hair colours depending on their ability to penetrate the hair shaft and the resulting durability of coverage, can be broken into temporary, semi-permanent, demi-permanent and permanent.
Temporary Hair Colour
Temporary hair colour does not penetrate the cuticle and sits on the outside of the hair. It is the simplest form of hair colouring and can be used to quickly mask grey hair for certain occasions but it only lasts till the next shampoo wash.
Semi-Permanent Hair Colour
Semi-permanent hair colour contains no ammonia and is similar to the temporary hair colour in that it can be applied directly from the bottle and does not penetrate the cuticle, so that the colour is only deposited on the outside of the hair and in the pores. However, unlike the temporary hair colour, it lasts longer, typically four to six shampoos and is more effective in covering grey hair.
Demi-Permanent Hair Colour
Demi-permanent hair colour contains no ammonia but is mixed with the developer (peroxide) shortly before application. The developer helps lift the cuticle so that the colour can be deposited outside and inside the cuticle and on the cortex. The molecules of demi-permanent hair colours are very small and they are therefore gradually washed out from the cortex, lasting about 15-20 shampoos.
Permanent Hair Colour
Permanent hair colours were designed to penetrate the cuticle and deposit their colour on the cortex. They usually contain some amount of ammonia and are mixed with the developer shortly before application. The developer lifts the cuticle and removes the original hair colour so that the new colour can be deposited under the cuticle inside the cortex of the hair. The newly formed pigment is a result of the chemical reaction between the developer and the aniline derivatives contained in the permanent hair colour, which produces molecules that are relatively large in size and get trapped inside the cortex. The permanent hair colour is typically used once every five to six weeks to cover the newly grown grey hair. It is the most effective way of covering white hair of all types of hair dyes but also the most destructive assault on your hair.
The most common problem faced with colouring grey hair, especially with demi-permanent and permanent hair dyes, is the difficulty of lifting and penetrating the cuticle. White hair is usually thicker and courser and its cuticle is thus more difficult to penetrate than that of normal, pigmented hair. Therefore, when dyeing grey hair, you have to apply colour on your grey hair first and let it work for a few minutes before applying the colour to all of your hair. However, hair dyes are not suitable for being applied selectively to keep certain grey areas untreated.
Progressive Hair Colorants
Progressive hair colorants are the best choice for covering grey hair for those of us who wish to do it gradually and discretely in the privacy of our own homes, while keeping some grey areas untreated in order to look more natural. Most of the progressive grey hair colorants are easy to apply as they do not require the use of plastic gloves. They do not contain ammonia or peroxide. First, the colorant must coat and penetrate the hair and then, as the mixture dries in the air, the chemical reaction, in the presence of atmospheric oxygen, turns its components into a synthetic pigment which remains deposited on the surface, in the pores and some of it also on the cortex of white hair. This synthetic pigment becomes a substitute for the missing melanin (natural pigment). The chemical reaction typically lasts till the next shampoo wash, so the less frequently you wash your hair the more effective these agents become. Progressive hair colorants mainly target your white hair, as they replace the missing pigment with a synthetic substitute. Their weakness is the need to apply them repeatedly, several times in order to achieve satisfactory coverage and the relatively few shades that are currently available.
Active Substances Used in Progressive Hair Colorants
SYNTHETIC PIGMENTS produced by hair colorants are products of the chemical reaction of one or more components contained in progressive hair colorant and atmospheric oxygen. They are either metallic salts or organic compounds. The most common metallic-based pigment is lead sulphate. Lead acetate is its better-known precursor and can be found in numerous hair colorants such as Grecian formula, GreyBan or Youthair. Bismuth sulphide is the other type of metallic pigment used (e.g. in Restoria) and bismuth citrate is its precursor. Organic pigments are polymers. Re-Nature is a typical representative of the organic-based, hair colorant, using 5,6-dihydroxyindoline as its precursor, which reacts with the oxygen in the air to produce melanin-like acting polymers.
LEAD ACETATE is a white crystalline substance with a sweetish taste. Like other lead compounds it is toxic and should not be digested. Its use in cosmetics products has caused a lot of controversy recently. However, its sweet taste has led to its use as a sugar substitute throughout history. In low concentrations, it is the most popular active ingredient employed in progressive hair colorants as a precursor to the synthetic pigment that is formed on the surface and inside the hair shaft. Although these products are currently available in pharmacies in Europe and in the US, some doctors warn about the risks associated with the potential absorption of lead acetate through the skin. Many grey hair sufferers have been using such products for years with very good success. To see satisfactory results, every time these lotions are applied you should allow them enough time to work (ideally two days) before washing your hair. Direct sun reduces the efficacy of lead-acetate based agents.