Available at most professional beauty-supply stores, protein filler, also known as hair colour filler, penetrates into your hair shaft and allows for an even distribution of hair colour. Protein filler corrects for hair that is too porous, green from chlorine pools and fading ends. You can purchase colours from the primary spectrum of red, blue and yellow and clear to counterbalance a colour job gone wrong. However, for most home-dye treatments, you may choose the clear or neutral shade as it will even out the porosity in your hair and allow for even penetration of the dye.
Purchase a neutral protein filler from your local beauty supply store. Colour will be clear.
Shampoo your hair. Rinse thoroughly with lukewarm water to remove all the shampoo and towel dry.
Pour filler into your hands. Start at the roots and work filler into your hair shaft. Apply more filler to the ends of your hair, as they are more porous than the root.
Allow filler to process on your hair according to manufacturer's instructions, usually from 5 to 10 minutes. Do not rinse out.
Apply your hair colour over the filler.
A neutral filler works best for most non-professional hair colours. Do not condition hair after you shampoo and before you apply filler, as conditioner will coat the hair shaft and not let filler penetrate.
If choosing a colour filler, you should consult the colour chart. Keep filler on hair when applying hair colour to even out the colour.