ABSTRACT
Abstract: Insoluble azoic colours are produced on cellulosics when a coupling component (preferably naphthol) reacts with diazotised aromatic base under specific conditions. The lake thus formed in situ remains trapped in fibre pores and cannot come out resulting good colourfastness. However, a part of lake formed at the fibre surface remains embedded at the interior to cause poor rubbing fastness. These colours are water insoluble and brilliant in shades, specifically used to develop all shades of red, orange, yellow and maroon.
