If you've ever gone to the hair color section of your drugstore you have seen hundreds of colors and formulas. It can be very confusing! Here are some explanations about the staying power of the hair dyes.
Temporary hair color is available in various forms including rinses, shampoos, gels, sprays, and foams. Temporary hair color is typically brighter and more vibrant than semi-permanent and permanent hair color. It is most often used to color hair for special occasions such as costume parties and Halloween.
The pigment molecules in temporary hair color are large and cannot penetrate the cuticle layer. The color particles remain absorbed (closely adherent) to the hair shaft and are easily removed with a single shampooing.
Temporary hair color can persist on hair that is excessively dry or damaged in a way that allows for migration of the pigment to the interior of the hair shaft. It lasts for about a few hours to 1 day.
Semi-permanent hair dye has smaller molecules than temporary dyes, and is therefore able to partially penetrate the hair shaft. For this reason, the color will survive repeated washing, typically 4–5 shampoos or a few weeks. Semi-permanents contain no, or very low levels of developer, peroxide or ammonia, and are therefore safer for damaged or fragile hair. However, semi-permanents may still contain the toxic compound P-Phenylenediamine or other such ingredients. ingredients.
The final color of each strand of hair will depend on its original color and porosity, so there will be subtle variations in shade across the whole head. This gives a more natural result than the solid, allover color of a permanent dye. However, it also means that gray or white hairs will not dye to the same shade as the rest of the hair. If there are only a few gray/white hairs, the effect will usually be enough for them to blend in, but as the gray spreads, there will come a point where it will not be disguised as well. In this case, the move to permanent color can sometimes be delayed by using the semi-permanent as a base and adding highlights.
Semi-permanent color cannot lighten the hair.
Demi permanent hair color is permanent hair color that contains an alkaline agent other than ammonia (e.g., ethanolamine, sodium carbonate) and, while always employed with a developer, the concentration of hydrogen peroxide in that developer may be lower than used with a permanent hair color. Since the alkaline agents employed in dem-perms are less effective in removing the natural pigment of hair than ammonia these products provide no lightening of hair's color during dying. As the result, they cannot color hair to a lighter shade than it was before dyeing and are less damaging to hair than their permanent counterpart.
Demi-permanents are much more effective at covering gray hair than semi-permanents, but less so than permanents.
Demi-permanents have several advantages as compared with permanent color. Because there is essentially no lifting (i.e., removal) of natural hair color, the final color is less uniform/homogeneous than a permanent and therefore more natural looking; they are gentler on hair and therefore safer, especially for damaged hair; and they wash out over time (typically 20 to 28 shampoos), so root regrowth is less noticeable and if a change of color is desired, it is easier to achieve. Demi-permanent hair colors are, in essence, permanent color and the darker shades in particular may persist longer than indicated on the packet.
All "permanent" hair color products and lighteners contain a developer, or oxidizing agent, and an alkalizing agent (most often ammonia).
When the tint containing the alkalizing ingredient is combined with the developer cause a chemical reaction that swells the hair permitting the tint to enter the cortex, where the melanin is located. The melanin is lightened and subsumed by the new color. The ammonia swells the cuticle of the hair to allow the color pigments to penetrate deep into the hair shaft.
Permanent color is truly permanent and will not wash out, although it may fade. New hair growth in the hair's natural color will contrast with the colored section of the hair.
Permanent hair dyes can be removed by bleaching, or stripping with a color remover. In the case of striping hair color, this process will only be effective if the original hair color is lighter than the dyed result. Theoretically a color remover will return hair to its natural color if the hair has been color treated but this process is damaging to the hair.
So when coloring at a salon is not an option, see what is in your local drugstore. Decide how long you want the color to stay, then select your own perfect shade, follow the directions (please do an allergy test first) and enjoy your brand new look!