Coloring grey hair – extra ammonia or extra peroxide?
A. Christine, the general rule of thumb is that higher alkalinity (especially in the form of ammonia) results in better color deposit. This is because the higher the alkalinity the more “open” the cuticles become. This is also why demi-permanent colors with lower alkalinity, even if used with high volume peroxide, tend to have less deposit and permanency than the more alkaline permanent colors.
High volume developers tend also to “loosen” the hair structure to some degree and they do that in the presence of alkalinity, acting as mild bleaches. In the case of resistant virgin grey hair, the hair structure is usually strong and the cuticles are well compacted. Ammonia here is generally more effective than peroxide in opening up the hair fiber. However, there comes a point of diminishing returns with both alkalinity and higher volumes of peroxide. Beyond an optimum level, which differs with differing hair types, the damage resulting from the excess of chemicals outweighs their added benefits.
It is always recommended to follow the manufacturer’s instructions of the hair colorant being used since various brands of hair color may have wide ranges of alkalinity. Whatever ‘tweeking’ that may work with one color may cause adverse effects with another. Keep in mind that in most cases you need to adjust neither the ammonia level nor the peroxide volume to achieve good grey coverage. Just make sure the hair is free of metallic deposits such as iron and copper because these metals interfere with color diffusion and deposit inside the hair and make the hair appear resistant to coverage.