Masao Nagata of Nagata Indigo Dyeing Works (長田染工場) in Izumo, Shimane demonstrates their hands-on dyeing process done just as in the olden days before mechanization.
First, he moistens the cloth before lowering it into a high-alkaline dye bath of fermented indigo and lye. Indigo appears green when lifted from the bath, but as it is rinsed in clear water and oxidation proceeds, it begins to turn its characteristic shade of blue, which will deepen with subsequent dips in the bath.
The studio where Masao and his father produce custom-order noren curtains, furoshiki wrapping cloths and more is one of just two left in Japan that specialize in tsutsugaki-zome dyeing, where patterns are drawn freehand using a rice-paste resist. Here Nagata-san Sr. holds an example. In addition to the rich indigo blue background, other colors are hand dyed with small brushes using Japanese pigment dyes.
You, too, can get a glimpse at everything that goes into this, in this excellent one-minute video