What happens when you over bleach?

Here is a good example!  This is a video from a college student who has attempted to bleach a mannequin head's hair. Although she used 30 volume she did put the head under the dryer which would have caused the bleach to turn volatile.

However (for those who have been lucky enough not to see or experience this), the video shows you exactly what happens to hair when you over bleach it. Bleach contains ammonia (which will swell the hair), coupled with the peroxide strength the chemical will go into the hair and start oxidizing (lightening out) the pigment. However, when the pigment is gone, the bleach will then attempt to start oxidizing the keratin and internal bonds. At this point the hair starts to dissolve and will turn to a gum texture.

Firstly, don't be so alarmed - generally it takes a huge amount of lightening to get the hair to this point. However, you need to remember that continual bleaching can make this happen. When I hear people saying they "want to go from black to platinum in one go" - this video demonstrates what I am afraid of.  Not to mention the damage it could do to your scalp. Notice the bleached hair on the  video clip looks fairly white.  Obtaining white (without a toner)  means the Keratin protein has actually been bleached away (hence the gummy texture). Keratin is yellow, so if you are lifting up - you should always see a yellow hue to the hair, which needs subsequent toning (as the yellow coloured keratin protein is still present in the hair). If you have got the hair to pure white from bleaching alone be careful!  With this in mind, never lift the hair to a pale yellow and think you haven't lightened enough and attempt to bleach again!  The pale yellow means you have lightened enough and a subsequent bleach application will literally destroy your hair.   Instead, when the hair has reached pale yellow it should be toned with a violet pigment.  Violet neutralises yellow and create pure white. 

Bleaching isn't necessarily dangerous, but you should always remember it's not a colour - it's only removing from your hair (not adding to it), so be careful how much you repeat the process on the same hair and if your hair feels very dry or damaged, never attempt to bleach it - as it will simply disintegrate. 

Remember, if you have bleached hair during any point of it's lifespan (and longer hair can be several years old), applying another bleach application may lead to over processing.  Many people forget (if they have coloured over bleached hair) that under the dark colourant - the results from the previous bleach are still in place.   Therefore, if you have coloured over bleached hair, you should always use a non peroxide or ammonia colour remover to take this shade out.  After this point, a bleach or lightener can be applied to the subsequent (darker) growth (only) and a toner applied throughout to create a true blonde. 



http://www.youtube.com/watch?v=a1InTn9JrmA