Learning Objectives
Understand the differences in chemistry and application of Group 1, 2 and 3 acid dyes on polyamides.
Know the causes of the barre nylon phenomenon and explain how to reduce it.
Evaluste the use of natural and synthetic tanning agents as after-treatments.

Consolidation Questions
1. Why are acid (anionic) dyes the most suitable for this type of fibre.
2. Compare the use of Group 1, 2 and 3 acid dyes for nylon in terms of substantivity, pH and dyebath conditions.
3. Explain the phenomenon of Barré dyeing and what can be done to reduce it.
4. State the differences between natural and synthetic tanning agents and give an example of each.
5. Compare and contrast the use of natural and synthetic tanning agents to aftertreat acid dyes on polyamide fibres