WHY IS MY HAIR BRASSY?
Because of the way hair color molecules are arranged, your hair can become brassy very easily. It's not a look that anyone wants, so understanding what is happening, how it happens, and what you can do about it will ease some of the frustration. Hair can be high maintenance even if the person to which it's attached isn't.
WHAT IS HAPPENING
Hair becomes brassy when the blue pigment molecules escape from the hair shaft. A single strand of hair is scaled with cuticles kind of like the scales of a fish. When the cuticle is open, moisture and color escape. The first color to go is blue, and blue is what gives your hair that cool tone. Brassy hair and dry hair tend to go hand in hand. Read more about the behavior of color molecules here.
WHAT CAUSES IT
The list of causes is long. You can open your hair cuticle by being out in the sun, using too much heat during styling, or showering with water that's too hot. Shampoos with sulfates can damage your hair strand, dry it out, and strip your color.
Sulfates are salts from sulfuric acid. Sulfuric acid is a corrosive chemical that oxidizes materials like metals and living tissues. The only purpose of putting sulfate in shampoo is to make it suds up for you.
Coloring your hair with permanent color or lightener causes brassiness. No matter what color you put on there, it uses peroxide to develop it. You stylist knows this and knows how to counteract the unwanted tones with the formula he or she uses. If you leave the salon brassy, then your stylist needs to address it. Brassy is not a color, it is what remains in your hair after the removal of color. If you leave the salon perfect, but turn brassy after a couple of shampoos, then you need to examine you hair-care routine to find the cause. Tones in hair color fade over time. Toners after lightening are only meant to last 4-6 weeks, which is the time you should be in for a touch-up anyway.
WHAT YOU CAN DO ABOUT IT
If you are spending money to get your hair colored at the salon, don't throw that out the window by not taking care of it at home.
Avoid using too much heat on your hair. If you use an iron every day, you're going to have trouble with more than just your color. You'll also sabotage growing your hair out long. Heat above 365 degrees will lighten your hair. If you have an iron that doesn't let you control the heat, it may be closer to 400 degrees, if not warmer. Make peace with your natural texture, learn how to give yourself a blowout, and reserve the heat for a special occasion.
Use sulfate free shampoo and know that you won't have a lot of suds when you wash. You can also use a shampoo and conditioner that have purple pigment added to it. Don't get something cheap just because it's purple. Use a good quality shampoo and conditioner like these from Kevin Murphy.
Keep up with your appointments. Even if you don't need a new highlight or color yet, you still need a color gloss to keep your hair fresh. A color gloss adds shine and tone to the hair while temporarily smoothing down the cuticle. It's fast and can be done in an hour appointment. This is especially necessary when you regularly get your hair lightened. In between each lightening appointment, you should come in for a color gloss. It's the only way to keep your hair the color it's supposed to be.