how does hairdye actually dye your hair?

Question: how does hairdye actually dye your hair?

Asked by chloejonasx to Betul, Bridget, Ceri-Wyn, Laurel, Maria on 18 Jun 2010 in Categories: General.
- Bridget Waller answered on 18 Jun 2010:
  
  No idea! One of lifes great mysteries… (although google can probably help fix that)
- Ceri-Wyn Thomas answered on 18 Jun 2010:
  
  I think hair is porous so it can absorb substances- so I guess the molecules in the hair dye bind to certain points on our own hair molecules. Temporary dyes have really large molecules that don’t penetrate right through to the centre of the hair strands. However, permanent dyes and bleaches use chemicals which- when added together cause a chemical reaction that swells the hair and allows molecules to enter the centre of the hair where the pigment molecules are (melanin). These molecules can then alter the colour of the hair pigment resulting in a permanent colour change. i hope that helps!
- Laurel Fogarty answered on 18 Jun 2010:
  
  Pigments in the dye either attach to the outside of the cuticle (the very outside bit) of your hair (for semi-permanent colours) or they go deeper and the pigment molecules go inside the hairs and give it a diffreent colour. For blonde colours there is often ammonia or another oxidising agent that will change the pigments that are already there in your hair.
  
  That was a hard question.

Question: how does hairdye actually dye your hair?