What is Hair Coloring?
Hair coloring is the application of color to the hair, to create a different look or appearance.
Level 1, semi-permanent color -- This product adds color without changing natural color dramatically. The hair color contains tiny color molecules that enter the hair's cuticle, or outer layer, and go into your hair's cortex. They don't interact with your natural pigments. And since the molecules are small, they eventually exit the hair shaft after several shampoos, leaving the hair as it was before treatment. This level generally lasts for 6 to 12 shampoos, covers up to 50 percent gray, enhances your natural color and leaves no roots. This hair coloring won't lighten your hair color because it contains no ammonia or peroxide.
Level 2, demi-permanent color -- This product level lasts longer, through 24 to 26 shampoos. In this process, pre-color molecules penetrate the cuticle and enter the cortex where they then partner to create medium-sized color molecules. Their larger size means they take longer to wash out. These products do not contain ammonia so the natural pigment can't be lightened. However, it contains a small amount of peroxide, which allows for a subtle, but noticeable, color enhancement. It also blends and covers gray. (Both semi- and demi-permanent colors can become permanent on permed or already-colored hair!)
Level 3, permanent color -- This is what you need for a more significant color change (to go from black to blond, you'll still need to go with a process called double process blonding and it'd be wise to get this it done professionally). In this level, both ammonia and peroxide are used. Tiny molecules enter all the way into the cortex, where they react and expand to a size that cannot be washed out. Your hair actually has to grow out over time. This product acts to lighten the hair's natural pigment to form a new base and then to add a new permanent color. The end result is a combination of your natural hair pigment and the new shade you chose. That means the color may appear different on you than on someone else using the same color. (That's why the "strand test" is so important -- more about that later.) Regular touch-ups of 4 to 6 weeks are generally needed to eliminate roots -- hair with your natural color growing at half an inch per month from your scalp.