what do u see…

• aq group (double bonded O)
• no water soluble group (SO3- groups)
• no charge (neutral/nonionic)

history of vat dyes:

• indigo and tyrian purple are naturally occurring vat dyes
  • indigo from plants, tyrian purple from shellfish
• synthetic indigo was first commercialized in 1897
• anthraquinone (AQ) based vat dyes were first commercialized in 1901

vat dye features

• colorants for cellulose or cotton
• water insoluble
• must be “vatted” for application
  • converted to a water soluble (leuco) form by an alkaline reduction process
• high WF and LF (applies to AQ vat dyes)
  • some causes catalytic fading or phototendering
• fixation mechanism= physical/mechanical entrapment