An article from Colour Lovers about hair color
December 19, 2007
I found this article that might interest you. It is not a hair based website, but a site for designers about all types of colors. There is some very good information here about the history of haircolor as well as a little bit of chemistry and might make conversations with your haircolorist more clear. I do have a few things that I want to clarify, however:
The longest-lasting of hair dyes, permanent color cannot be washed out. It contains both ammonia and peroxide, which raise the cuticle of the hair in order to allow the tint to penetrate to the cortex and lighten the hair by breaking up the melanin that gives hair its natural color, fundamentally changing the shade of the hair. Since the color is (true to its name) permanent, bringing hair back to its original color requires a new dye job.*
*When exposed to the ammonia and peroxide contained in permanent color, hair is permanently changed. While you can re-color it and change the shade, it is unreasonable to expect a return to your “natural color.” Once your hair is colored with alkaline tint (permanent color), it is never going to look like it did before it was colored. When we “tint back to natural,” we are doing our best to approximate what natural looks like.
Demi-permanent dyes last about twice as long as semi-permanent color. These dyes have smaller molecules than those of semi-permanent tinting formulas, so are able to penetrate the hair shaft to a slightly greater degree. Like semi-permanent dyes, however, this type of color contains no ammonia and thus cannot lighten hair, only add color to it.*
*Demi colors vary in their pH depending on the manufacturer and while they are generally free of ammonia, their can be other alkalizing ingredients. But they do have an activator (usually hydrogen peroxide in a weak solution). So while it can not, in theory, lighten the hair because of the lack of ammonia, if the product is of a high enough pH, or if the hair is fine enough (or has previous swelling from alkaline tint or other damage) it can lift and it can be permanent. If it grows out and leaves roots, then it’s “permanent” no matter what the box says.