Chapter 4 145 One of the major drawbacks of bleach products is their incompatibility with conventional oxidative dye precursors and the dyeing process. There is a small selection of direct dyes that can be used in bleach formulation but the achievable shade range is small (refer back to the Direct Dyes section for details). In most cases the high bleaching power of the product also rapidly oxidizes the dye chromophores and destroys the color. To deliver color with lightening, a two-step process is used an initial bleach to lighten the hair followed by a Level 2 or direct dye product to give the final color. There are only a select number of direct dyes that have some stability in the presence of bleach products, including some acid dyes, azo and disperse dyes. Examples include Acid Orange 7, Acid Yellow 1, Disperse Red 17, HC Blue 15. The ability of bleach products to oxidize dyes can be used to an advantage in the salon or by consumers who want to remove dye from previous coloring. For example, if they have colored to dark brown but decide they want to shift to a significantly lighter color, they could use a strong bleach to quickly get to this transformation. However, it should be noted that this method of color removal is not always completely successful, especially for dark shades, and may result in significant hair damage. An example of a typical bleach powder product is given in Formula 4. Formula 4 Persulfate Powder Product Ingredient Wt. % Function Potassium persulfate 61.69 Oxidant Ammonium persulfate 22.37 Oxidant Sodium metasilicate 13.56 Alkalizer Silica 1.49 Stabilizer Sodium lauryl sulfate 1.19 Solubilizer EDTA 1.19 Stabilizer Hair that has been lightened by bleaches will often have an orange/red color, making it look unnatural in the face of naturally