The Naked Scientists

The Naked Scientists Forum

Author Topic: How does bleach cause colour loss ?  (Read 4085 times)

Offline chris

  • Neilep Level Member
  • ******
  • Posts: 5337
  • Thanked: 65 times
  • The Naked Scientist
    • View Profile
    • The Naked Scientists
How does bleach cause colour loss ?
« on: 03/09/2004 10:52:26 »
What is the nature of the 'bleaching' effect brought about by chlorine or hypochlorites ? How does it compare with bleaching your hair with, say, peroxide.

Chris

"I never forget a face, but in your case I'll make an exception"
 - Groucho Marx


 

Offline Ylide

  • Moderator
  • Hero Member
  • *****
  • Posts: 905
    • View Profile
    • http://clem.mscd.edu/~mogavero
Re: How does bleach cause colour loss ?
« Reply #1 on: 03/09/2004 11:33:23 »
Good question.  When you use bleach, think about what you're trying to take the color out of:  organic dyes.  Most highly colored organic material (called chromophores) contain delocalizedl electron system, usually from conjugated double bonds.  When you use chlorine bleach, you're essentially exposing the chromophore to a powerful oxidizing agent as well as dissolved elemental oxygen.  The oxidation of the chromophore distrupts its chain of electron delocalization, causing light absorption to fall into a different range, often right out of the visible spectrum.  (i.e. the dye is no longer visible at all)

"Bleaching" your hair with peroxide (something of a misnomer as you're not using bleach) accomplishes essentially the same thing.  The oxygen radicals created when hydrogen peroxide decomposes will react with the pi electron system of the chromophores that make up your hair color, causing a color change.  



This message brought to you by The Council of People Who Are Sick of Seeing More People
 

Offline chris

  • Neilep Level Member
  • ******
  • Posts: 5337
  • Thanked: 65 times
  • The Naked Scientist
    • View Profile
    • The Naked Scientists
Re: How does bleach cause colour loss ?
« Reply #2 on: 03/09/2004 15:56:13 »
Wow - beautifully answered. Nicely done.

Chris

"I never forget a face, but in your case I'll make an exception"
 - Groucho Marx
 

The Naked Scientists Forum

Re: How does bleach cause colour loss ?
« Reply #2 on: 03/09/2004 15:56:13 »

 

SMF 2.0.10 | SMF © 2015, Simple Machines
SMFAds for Free Forums