Demi-permanent hair color - which some people mistakenly call semi-permanent lasts from 12 to 24 shampoos. It contains a small amount of peroxide - which means a small amount of hair damage - but no ammonia, making demi-permanent color a midway option between semi-permanent and permanent color. True to its middle-of-the-road position, demi-permanent color does a bit more than semi-permanent. First off, it stays in hair longer before fading away. In addition, demi-permanent color's slightly more opaque formula does a better job of darkening hair more than three levels, covers gray better, and boasts more power to brighten hair.
That tiny amount of peroxide can lighten hair, but only slightly - usually less than half a level. Again, if you have dark hair and dream of light locks, demi-permanent color is not for you. How do semi- and demi-permanent colors fade? Shampooing loosens their pigment molecules, causing color to progressively diminish until all the molecules are gone. Because of this, you'll never experience telltale roots with semi- or demi-permanent color. Permanent hair color As its name implies, permanent color stays on your hair permanently. Its tenacity becomes especially apparent when the colored strands grow out: you'll see a line of demarcation between them and the new, untreated root growth.
This, and the damage permanent color can cause (the formula contains both peroxide and ammonia), are its negative aspects. On a more positive note, with permanent hair color you don't need to worry about losing the color you love after 6 or 24 shampoos, you get superior gray coverage, you can brighten or darken hair as dramatically as you like, and you can lighten hair up to four levels. Be aware, however, that if you'd like to lighten hair more drastically, you're better off with double-process color. Permanent color can lighten hair only so much go beyond four levels and it won't be strong enough to remove all the natural melanin in your hair. The not-so-gorgeous result? Strands that are brassy; brassy, brassy.
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