Bleach has gotten such a bad reputation over the years, but while bleaching the hair can be damaging in the hands of the unexperienced, when performed correctly it is the only way to achieve certain haircolor results. When performed by a skilled stylist, bleaching the hair is no more damaging than any other chemical service, such as perming or chemically straightening the hair.
What is so great about bleach? For starters, it is the only way to lighten dark hair color in order to achieve ultra-light pale and platinum blondes. While permanent hair dye has the ability to lighten hair a few shades, dye alone is simply inadequate when it comes to going from extremely dark to extremely light. Permanent hair dye only has the ability to lighten virgin hair, or hair that has never been chemically processed. For example, hair that has been dyed brown can only be made blonde with the use of bleach. Simply putting a blonde shade of dye on hair that has been dyed brown will have absolutely no effect on the hair (except for perhaps turning the roots orange)!
The reason why bleach has gained a reputation for damaging the hair is because many stylists do not understand how to mix a bleach formula. Although there are several different types of bleach, the most popular bleach for salon use is powdered bleach. This powder must be mixed with a hydrogen peroxide developer in order to lighten hair. Developer comes in different varieties, based on the oxygen content of the developer. There are four popular "strengths" of developer: 10 volume, 20 volume, 30 volume, and 40 volume. Of these formulas, 10 volume has the lowest oxygen content and 40 volume has the highest.
This is where most hairstylists make mistakes. They assume that 40 volume developer is "stronger" and that 10 volume developer is "weaker". This is a common fallacy, even among experienced stylists. The truth is that 10 volume developer isn't any stronger or weaker than a 40 volume developer; it just takes longer for a 10 volume developer and bleach mixture to lighten the hair because of the reduced oxygen content. As a result, many stylists will mix powdered bleach with 30 or 40 volume developer in the misguided belief that they will be able to achieve a lighter result.
The truth is that 20 volume developer will lighten hair just as much as a 30 or 40 volume developer- it just takes more time. The damage to the hair occurs when this process is sped up with the use of heat or a high-volume developer. In other words, the faster the hair is lightened, the more damage that will occur. When a client with black hair wants to become a blonde, many stylists will automatically mix powdered bleach with 30 or 40 volume developer and then stick the client under a heated dryer. While this method will quickly lighten hair, it may also cause irreparable damage. On the other hand, if the stylist had mixed the bleach with a 20 volume developer and processed the client's hair at room temperature, it would take longer to get to blonde, but the hair would be much healthier as a result.
Bleach that has been exposed to the air for too long may become weak after a while, so if your goal is to lighten dark hair to a very pale blonde, it may be necessary to wipe the bleach off the hair and re-apply a fresh mixture after fifteen or twenty minutes.
By bleaching hair the proper way, you can achieve the results you want with minimal damage to your hair. But, as always, coloring or bleaching the hair is best left in the hands of a skilled and experienced professional.