Chapter 4 131 The final shades typically use a combination of the different primary intermediates and couplers to achieve the final color. In this way a wide range of shades can be formulated from neutral to tonal shades. A typical shade will contain two to five primary intermediates and two to five couplers depending on the share required. Most companies use a very similar palette of dyes due to availability, performance and regulations, and although there are several patented dyes that are restricted in use, with the available dyes a wide range of shades can be formulated. A list of key dyes used in current products is shown in Table 4. The components of the coloring system (i.e. the alkalizer, the oxidant and the dye precursors) need to be formulated into a system that is aesthetically pleasing and can be easily applied to the head, not be drippy, be easily removed after use, and deliver the lightening and color performance as desired, even if the product has been stored on the shelf for up to three years. To meet these criteria the oxidant and the dye precursors must be separated before use to ensure stability of the hydrogen peroxide and that no reaction occurs between oxidant and dye precursors resulting in dye formation in the container and therefore a product that no longer dyes hair. Thus the consumer receives the product in two bottles, which she mixes together immediately before use. The first bottle, usually called the developer, contains the oxidant which is typically kept at an acidic pH to maintain its stability. The second bottle, called the tint, contains the alkalizer and the dye precursors at an alkaline pH of ~9.5-10.5. The final mixed pH is ~9.8-10.3 which is