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If you feel like you change your hair color as often as you change your handbags, semi-permanent hair color may be for you. Semi-permanent hair color will wash out of your hair over time -- unlike the permanent dye that you can’t get away from until your hair grows out. Remember different hair dyes, different rules: You’ll apply semi-permanent dye to damp hair (unless you don’t like your hair color to actually take effect).
Permanent Versus Semi-Permanent
Think of semi-permanent hair color as the less-damaging little sister of permanent hair color. To reach your hair shaft with permanent hair color, your stylist has to apply ammonia, which opens up your hair shaft. Sure, that makes it work, but it also damages your hair (ouch!). Semi-permanent hair color doesn’t use ammonia because it dyes the outside part of your hair shaft and doesn’t mess with the hair color inside. For semi-permanent hair dye, the dye soaking in too much can be a bad thing.
It’s All About Porosity
When it comes to dye and your hair, there has to be a good balance between porous and not-too-porous. Porosity isn’t a class in school -- it’s a measure of how much things soak into your hair. If your hair is too porous, it gets damaged. That’s why you want your hair to be damp when you dye it with semi-permanent hair: The dampness helps to keep the dye from soaking too far into your hair. If it does, your hair color will look much brighter/darker/lighter (however you dyed it) than you intended. As an added problem, the dye will come out of your hair faster, too.
Why Damp Works
Just like hair that’s too porous doesn’t work, hair that’s not porous enough doesn’t either. If your hair is soaking wet instead of damp, the hair color can’t soak in at all. You want to strike the right balance when you apply semi-permanent hair color. After shampooing your hair, wring it out and dry gently with your towel. It shouldn’t be dripping, but it shouldn’t be dry, either.
If you finish dying your hair and follow the instructions to a “T,” but still have a few areas where your color seemed to deposit more heavily, this can be a sign that you didn’t get it quite right with the dampness/wetness factor. One way to make things more even is to comb through your hair before applying the dye to distribute water more evenly. Other factors can be to blame, however, including that some areas of your hair may be more damaged than others. Try to keep your hair in the best condition possible between treatments by moisturizing your hair, and your semi-permanent color will likely go on more evenly.