Dyeing Blue with Japanese Indigo — The Fresh-Leaf Salt-Rub Method

Use 200-300% WOF of fresh Japanese indigo leaves. For 100 g of wool, harvest 200-300 g of fresh leaves. Pick leaves in the morning after the dew has dried — indican content is highest at this time. Strip leaves from stems and discard the stems (they contain little dye). Use the leaves immediately — indican begins degrading within hours of harvest. The leaves should be bright green and healthy-looking. Wilted, yellowed, or insect-damaged leaves have lower dye potential.

Place the fresh leaves in a blender with 500 ml of cold water. Blend for 30-60 seconds until the leaves are thoroughly pulverised into a green slurry. Work quickly — the indican begins converting to indoxyl as soon as the cell walls are broken. Strain the green slurry through a fine mesh strainer or muslin cloth into a bowl, pressing firmly to extract all liquid. The strained extract will be a murky green. Discard the leaf pulp.

Add 2 tablespoons of salt to the leaf extract and stir to dissolve. The salt helps draw the dye into the fibre. Add enough cold water to cover the wool — approximately 2 litres total. Pre-wet the wool in cold water (no mordant needed for indigo). Lower the wool into the extract. Work the extract gently through the fibres with your hands, squeezing and turning for 10-15 minutes. Keep the wool submerged. The extract will slowly change colour as the indoxyl is absorbed by the fibres.

Remove the wool from the extract, squeeze gently, and spread it out in the air. Watch the colour transform: the green-tinged wool will turn blue within minutes as the indoxyl oxidises to indigotin on contact with atmospheric oxygen. This is the same magical colour change that happens in a traditional indigo vat, but happening from a simple leaf extract. Turn the wool to expose all surfaces to air. Allow 20-30 minutes for full oxidation.

For deeper blue, return the wool to the extract and work through the fibres again for 10 minutes. Remove and oxidise for 20 minutes. Each cycle adds another layer of indigotin. The fresh-leaf method produces lighter blues than a fermentation vat — expect pale sky-blue to medium blue from 3-5 dips. If making a fresh batch of extract for additional dips, harvest and process new leaves (the first extract will be exhausted after 3-4 uses).

After the final oxidation, rinse the wool in lukewarm water until the runoff is clear. Some green leaf pigment (chlorophyll) may wash out — this is normal and desirable, as chlorophyll is not lightfast but the blue indigotin is. The final colour is a soft, clear sky-blue to medium blue — lighter and more delicate than vat-dyed indigo but with the same excellent lightfastness. The blue will not fade significantly with washing or sunlight, as indigotin is among the most stable natural pigments. Dry in shade or sun — indigo is stable to light.