The following comes from another thread in MUT regarding protein fillers:
Description: Insures marvelous color results by equalizing hair porosity. Repairs protein bonds and protects against chemical damage. Seals color, adds body, volume and sheen.
Directions: Apply to towel damp hair. Apply colour after 20 minutes. Do not rinse.
Ingredients: hydrolyzed keratin protein, hydrolyzed wheat protein, keratin amino acids.
You may find that your hair has reached a point that it just won't hold color anymore. It is likely that you have damaged your hair shaft so that the color molecules just wash away rather than getting trapped inside.
Head down to your local beauty supply store and pick up something called protein filler. They sell protein fillers in various shades but I always choose the neutral protein filler, which is clear. A large sized bottle of neutral protein filler costs around $5.00 and will make all the difference in the world with how your dye job comes out.
Get a box of hair dye and have everything ready like you are going to dye your hair.
Start by getting your hair damp and then saturate it with the protein filler. Once you have the protein filler on your hair you will need to let it set for 20 minutes.
After 20 minutes you are ready to dye your hair. DO NOT rinse the protein filler out of your hair before dying it. Just apply the hair dye like normal right over the top of the protein filler and follow the timing instructions on the box of hair dye for how long to leave it in. When the time is up rinse your hair thoroughly and condition it using the conditioner that came with your hair dye.
Protein filler works to help seal the color into your hair shaft so it will last longer. Not only that, but it helps the color go on more evenly so you don't have spots that are darker or lighter and it helps to repair the damage to your hair at the same time.
While your hair dye may not last as long as if you had applied it to virgin hair, it will last much longer than it would without using the protein filler. Apply any leftover protein filler to your hair periodically to help condition your hair and keep it in great shape.
