The nature of the variations in continuous‐filament nylon and their influence on dyeing behaviour are explained. By the use of a special fabric containing yarn differing in physical and chemical properties by known and controlled amounts, the sensitivities to such variations of many dyes for nylon have been assessed. These results appear in the appendix in tabular form, and are intended to help the dyer to select suitable dyes, by indicating their abilities to cover yarn irregularities. New and current dyeing methods are discussed, and suggestions are made for improved uniformity. Laboratory investigations have shown which new methods offer most prospects of success, and also where more detailed investigation will be of value.

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