Filtration Completion
Proceed to aeration: • Stir/add air to the indican liquid with kayak paddles (traditional method) OR Automate using a sump pump + PVC pipes to circulate like a fountain. • Aerate 30–60 min, until liquid turns blue–dark dark greenish blue—this means indigo particles are forming. ▪ Test: Remove a pint jar of the liquid, sprinkle some pickling lime, and stir. Let it settle for a few minutes. If blue sediment settles and leaves clear brown liquid on top, you are ready to stop aerating!
*Optional: When aerating, excessive bubbles may form and start to come out of the vat; you can sprinkle a few drops of neutral oil to dissolve them quickly.
◦ Add pickling lime (calcium hydroxide, Ca(OH)2): ◦ Mix a few tablespoons of lime with some vat liquid in a small bucket. ◦ Slowly pour the slurry back into the trough. ◦ Add gradually, checking pH often with a hand-held meter—target pH 10. Hand-stir gently with a wooden stick and check the pH. ◦ Avoid adding too much lime, which will make the final pigment less pure.
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