Some people shy away from the notion of coloring their hair because they do not wish to permanently alter their look or deal with color upkeep. With the wide range of hair color products available, however, it is in fact possible to give the hair a makeover that lasts anywhere from one day to six weeks. Hair color products generally fall under four main categories: permanent, demi-permanent, semi-permanent, and temporary.
Permanent hair coloring kits are perhaps the most familiar hair color product. This type of dye contains a chemical substance — usually ammonia — which, when applied to the hair, causes the shafts’ outer layers to swell. The formula then penetrates each hair shaft, lightening its natural pigmentation and depositing a new tint which “overrides” the now-lightened natural color. As its name suggests, this type of hair color is indeed permanent, and will not be affected by washings. It normally needs to be touched up every six to eight weeks, however, to avoid the appearance of contrasting roots.
Demi-permanent hair color products are quite similar to permanent products, but their results typically last only three to four weeks. The main factor that distinguishes demi-permanent dyes from permanent ones is that the hair-swelling chemical they contain is gentler than ammonia. While this chemical allows the new tint to penetrate the hair shafts, it does not lighten the hair’s natural pigmentation. As hair treated with demi-permanent color remains closer to its original shade than that treated with permanent color, emerging roots tend to be less conspicuous. One drawback to demi-permanent products, however, is that they generally cannot be used to make the hair lighter than its natural shade.
Those who would like a change that is more temporary might consider semi-permanent hair color products. In most cases, these coloring systems contain no hair-swelling chemical agent. Instead, they consist of a tint made up of very small molecules. The small size of these dye molecules allows them to partially enter the hair shafts, creating the appearance of an altered color. Generally, this type of hair color washes away in four to seven days.
Finally, temporary hair color products are a good choice for those who want a very short-lived hair makeover. This type of product contains large color molecules which do not enter the hair shafts, but rather sit on top of them. It is generally sold in gel, shampoo, spray, or foam form, and usually disappears after one washing. Temporary hair color is often available in bright, unnatural shades such as hot pink and neon blue, and consequently tends to be a novelty or costume product.