Semi-Permanent Hair Dye
When you see hair dye that is labeled "semi-permanent" this doesn't mean it will wash out immediately. Semi-permanent hair dye will eventually wash out, but usually after a substantial number of washes.
So why use semi-permanent hair dye and not permanent hair dye that won’t wash out?
One of the major reasons people opt for semi-permanent hair dye is that it is generally less damaging than permanent hair dye products. The chemicals and ammonia in permanent commercial hair dyes change the structure of the hair shafts, resulting in a changed hair color that will have to grow out from the roots over time. There is absolutely no doubt that the process is damaging, although you can minimize damage by using conditioning products whenever you wash your hair.
The ingredients and colorants contained in semi-permanent dyes, on the other hand, coat the hair rather than permeating right into the shaft and cuticles. Even if molecules of color do get into the shaft – which they might if the product contains a small amount of peroxide – once you have shampooed your hair anything from 20 to 30 times (depending on the product), the color will be minimized and basically dislodged.
Often people whose hair is starting to turn grey chose semi-permanent hair dye products, so that they basically re-dye the graying roots. Not only is it a gentler process, but it presents the option to change the color of your hair if you want to. Having said this, it is also true that if your intention is primarily to wash away the gray, then it is best to choose a color that is as close as possible to your natural color.
Another advantage of semi-permanent hair dye is that it is relatively easy to get rid of. If you find you don't like the color of semi-permanent hair dye, you can also speed up the removal process by using a proprietary "cleansing" or clarifying shampoo. You will undoubtedly find that you need to repeat the process several times; and you will need to use a "deep" conditioner to help restore your hair to a healthy condition.
Another more drastic process you can use to get rid of semi-permanent shampoo is hot water and baking soda. All you do is rinse your hair with hot water so that the hair cuticles open naturally; then cake baking soda onto your hair and rub it in. Leave it on for two or three minutes before rinsing off with fresh water.
Baking soda, which you will find on the shelves of supermarkets and grocery stores, is a type of acid. While it will help to get rid of the dye more quickly, it will also inevitably dry out your hair. The best solution for this is to give it a hot-oil treatment. You can get this done at a salon, buy a kit that you can use at home, or mix up and warm equal quantities of canola and olive oil which you then apply to your hair. Wrap up your hair in a warm towel or wear a shower cap for half an hour before rinsing and shampooing to remove all the oil.
If you aren't sure whether a semi-permanent product is the best for your needs, or would rather have your hair colored professionally it may be worth asking for advice.