Why hair dye packs don't include an acid ammonia neutralizer?

They add ammonia to open the hair cuticle and allow dyes to penetrate better.

But why they don't include a separate acid-containing neutralizer, to be used when rinsing off excess dye?

Comments

  • PerryPerry Administrator, Professional Chemist
    Because you can rinse it off with water.
  • Thanks @Perry ; but wouldn't it be be better to both

    lower hair pH beyond what water rinsing can (for a smooth feeling hair)
    and provide a quicker and more complete neutralization, as to avoid further hair damage?
  • PerryPerry Administrator, Professional Chemist
    I just don't think there is much evidence that using an acid rinse would provide significant benefits over just using water.  The amount of water used in rinsing would overwhelm any residual ammonia left on the hair. And if they use a shampoo after, those will usually have an acidic pH (5.0). So, no I don't think it would be measurably better to use both. (Perhaps theoretically it might be better).
  • DuncanDuncan Member, Professional Chemist
    They usually contain a conditioner for application post rinse. (Ones I've applied anyway. These are typically acidic and will neutralise any ammonia residues
    UK based, Over 20 years in Toiletries, After a 5 year sabbatical doing cleaning products, back in the land of Personal Care
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