Indigo with Characteristic Colors

Abstract

This paper presents data on indigo coloration and discusses the characteristics of indigo coloration. The blue color dyed with indigo is versatile. The hue changes with the lightness of the color, with a greenish tint in light colors and a reddish tint in dark colors. A pure blue color with a hue angle of 270° for slightly darker colors with L^＊ of 25 to 40. The blue color of indigo has low chroma.
In the analysis of old indigo-dyed fabrics, not all of them were dyed only with indigo. Before the modern era, the dark blue color of the common people in Japan was sometimes mixed with indigo and other colorants. Synthetic dyes such as tsuya-indigo, which have a different molecular structure from indigo, were sometimes regarded as a type of indigo dyeing. Tsuya-indigo dyes a brighter color than indigo, it can be differentiated by its secondary derivative spectrum.
The coloring of silk from the indigo vat dyeing method and the raw leaf dyeing method was not the same. The raw leaf dyeing method was characterized by a greenish blue color. The color of silk dyed with red colors such as indirubin was a warm purple or red, but with low chroma.

graphical abstract