1-2-3 indigo vat uses fermented indigo powder, calcium hydroxide, and fructose to induce a chemical reduction process. This process separates the indigo molecule, allowing it to bond and attach to fabric. Fabric is dipped in timed increments then allowed to air-dry where the indigo oxidizes from green to blue. Each dip builds layers of color.
Vat recipe/instructions from Botanical Colors and natural textile dyer, Michel Garcia. His technique is based on the traditional indigo vats of India, Morocco, and Provence that relied on reduction: where excess oxygen is removed from the vat using a mineral alkali (calcium hydroxide, or slacked lime) and a natural reducing agent (fruit sugar). This reduction separates the indigo molecule, where it can then attach + bond to fabric.
(1) part organic indigo (not water-soluble; requires reduction) (2) parts calcium hydroxide (alkalizes the vat and dissolves the indigo) (3) parts fructose powder (fruit sugar that removes excess oxygen from the vat)