A. Cotton Dyeing Procedure (Midnight Blue)
Step 1: Preparation
- Scour cotton thoroughly to remove impurities for better dye uptake.
- No mordant needed for indigo since it is a vat dye.
Step 2: Indigo Vat Preparation
- Prepare indigo vat with reduced indigo solution.
- Typical indigo concentration: 3-5% owf (3-5 g per 100 g fabric).
- pH: Alkaline 11-12 (maintained using lime and sodium hydrosulfite as reducing agent).
- Temperature: 25-30°C (room temperature).
Step 3: Dyeing
- Dip cotton into reduced indigo vat for 2-3 minutes.
- Remove and expose to air for oxidation (color develops).
- Repeat dipping and oxidation cycles 4-6 times to build deep Midnight Blue.
- M:L ratio: 1:20 recommended for even dyeing.
Step 4: Rinsing & Drying
- After final dip and oxidation, rinse cotton in clean water to remove unfixed dye.
- Wash with mild soap to remove excess indigo.
- Shade dry to preserve color intensity.
B. Silk Dyeing Procedure (Midnight Blue)
Step 1: Silk Preparation
- Scour silk gently with mild detergent.
- No mordant needed.
Step 2: Indigo Vat
- Same as cotton, 3-5% owf indigo, pH 11-12, 25-30°C.
Step 3: Dyeing
- Dip silk for 1-2 minutes per dip (silk is more delicate).
- Air oxidation between dips.
- Repeat 4-5 dips to reach desired depth.
Step 4: Rinse & Dry
- Rinse gently in cool water.
- Shade dry.
C. Wool Dyeing Procedure (Midnight Blue)
Step 1: Wool Preparation
- Scour wool with mild soap, avoid felting by gentle handling.
- No mordant needed.
Step 2: Indigo Vat
- Indigo concentration: 3-5% owf.
- pH 11-12.
- Temperature: 25-30°C.
Step 3: Dyeing
- Dip wool for 1-2 minutes per dip (to avoid felting).
- Air oxidation between dips.
- Repeat 4-5 dips.
Step 4: Rinse & Dry
- Rinse gently to remove unfixed indigo.
- Shade dry to preserve color.
Summary of Parameters (Midnight Blue – Indigo multiple dips)
Explanation & Reasoning:
- Indigo is a vat dye and requires alkaline pH and reducing agents to become soluble and penetrate fibers.
- Multiple dips with oxidation build up rich dark navy color.
- Different dip times for cotton, silk, and wool accommodate fiber sensitivity and avoid damage.
- No mordants needed because indigo chemically bonds during oxidation.
- Shade drying avoids UV fading and keeps color vibrant.