Brown Color Extraction from Walnut Hulls
Walnut hulls (the outer green or brown casing of the nut) are rich in juglone, tannins, and polyphenols, which produce deep brown to sepia-colored dyes. The color intensity depends on the hull’s ripeness, extraction method, and pH conditions.
Collection & Preparation
- Green Hulls: Collected from freshly fallen walnuts. They yield a lighter, golden-brown color.
- Brown (Aged) Hulls: From mature or decomposing walnuts. These produce darker, richer browns.
- Sustainability: Fallen hulls are preferred to minimize tree damage.
- Hulls are washed thoroughly to remove dirt and impurities.
- Damaged or moldy hulls are discarded.
- The hulls are cut or crushed into smaller pieces to increase the surface area for better pigment release.
- Sun-drying or low-heat oven-drying (below 60°C) can concentrate the pigments for a stronger dye extract.
Extraction Methods
- Water Extraction (Traditional Decoction)
- Alcohol Extraction (For Deeper Pigments)
- Fermentation-Based Extraction (For Rich, Aged Tones)
- Steam Distillation (For Essential Oils & Pigments)
Filtration & Purification
- Centrifugation or fine filtration removes unwanted particulates.
- pH Adjustment stabilizes the color and prevents fading.
Concentration & Storage
- Liquid Extracts: Stored in dark glass containers at 4–10°C to prevent oxidation.
- Powdered Extracts: Freeze-dried or spray-dried for long-term storage and easy use.
Applications of Yellow Pigment
- Textile Dyeing: Used for natural wool, cotton, and silk fabrics, creating warm brown hues.
- Wood Stains: Provides a rich, earthy brown finish for natural wood coloring.
- Inks & Paints: Incorporated into eco-friendly, natural inks and artistic paints.
- Cosmetics: Added to natural hair dyes and organic skincare products.
Would you like a detailed guide for large-scale industrial production?
