From the Maiwa website: Natural indigo is an extract prepared from cultivated plants of Indigofera Tinctoria. Indigo is the only source of blue in the plant world. Its ability to produce a wide range of blues has made it the most successful dye plant ever known.
What you see below is a fruit vat. This one is made with bananas, but you could make it with mangoes instead. To make a litre of dye you take one very ripe banana, mash it up and add 1/4 c water. Keep mixing this and then add 1 TBS of indigo dye powder. Add a bit more water and then add 2TBS hydrated lime. Keep mixing and add enough water to make one litre. The pot you see below is 10 litres. . . . so it started with 10 mushy bananas.
These are cotton and rayon samples dyed in the fruit vat.
Then of course we had to play with silk and cotton scarves to see how quickly the dye sinks into those fibres. And nothing like a good gate to hang the skeins and scarves as they oxidize.
And here is the total collection of samples I did. Each one had a couple of dippings as I tried to get more intense colour. They continue to oxidize and deepen in colour.
I won't even pretend to understand the chemistry of indigo, yet. It is something of a mystery, but hopefully not for long.
Ann has graciously offered to put up more dye vats and we can continue to play and learn.