Hair Coloring 126 scale. The level of lightening from a low hydrogen peroxide shade is between 1 and 2 levels (e.g. from a dark blonde to a medium blonde) and for a high hydrogen peroxide shade is between 3 and 4 levels (e.g. from a dark blonde to a lightest blonde). If more lightening is required then a pre-bleach step is often used (e.g. if the required change is from a dark brown to a light blonde). An alternative lightening chemistry has been recently introduced that works at the lower pH of 9 vs. 10. This chemistry utilizes the peroxycarbonate ion as the species that bleaches the melanin chromophores. It is formed in-situ from the reaction of hydrogen peroxide with hydrogen carbonate, as shown in Eq. 4. Ammonia is still required for the lightening and can come from using ammonium carbonate in the final formula, which can act as a source of both ammonium ions and hydrogen carbonate ions.9 This oxidant has advantages in reduced hair damage due to its lower pH, but it can also be used to generate higher lightening by using high levels of hydrogen peroxide and high levels of hydrogen carbonate ions. O C -O OH + HOOH O C -O O OH Peroxymonocarbonate ion Eq. 4 Color Formation The strategy in a Level 3 permanent colorant to deliver color that is wash resistant for greater than 24 shampoos is to use synthetic small uncolored dye precursors. These dye precursors penetrate inside hair where they are oxidized to form chromophores which are trapped inside the hair by their larger size and reduced solubility in water.10 The alkalizer in the colorant product (either ammonia or ethanolamine) enables this process by swelling the hair and increasing the rate of penetration of the dye precursors into the hair.11 Changing the structure of the dye precursors allows for a full range of shades including blacks, browns, auburns, reds, coppers, and golds. The first