The indigo dyeing process defines denim’s characteristic blue.
Rope Dyeing
Established around 1915, rope dyeing bundles 380-420 warp yarns into ropes and dips them 6-12 times in indigo vats. This creates a ring-dye effect where only the surface absorbs indigo, leaving the core white. This structure produces denim’s distinctive fading patterns.
Slasher Dyeing
Introduced in the 1970s, slasher dyeing passes yarns through dye baths in a flat sheet. More efficient but produces more uniform coloring with less dramatic aging contrast.
About Indigo
Since BASF industrialized synthetic indigo in 1897, virtually all commercial denim uses synthetic indigo. Its low fiber affinity is what enables denim’s unique fading.
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