Grey to black color extraction
Oak Galls are rich in tannins, which react with iron salts to produce grey to deep black shades.
Extraction Methods
- Use dried oak galls (crushed into small pieces or powdered).
- Add galls to distilled water and simmer at 90°C for 1-2 hours.
- This extracts the tannic acid.
- For black color: Add iron sulfate (FeSO₄) or rusted iron objects.
- Let the solution sit for 24-48 hours for full oxidation.
- Filter the extract to remove solid residues.
- Acidic pH (vinegar, citric acid) → Lighter grey
- Neutral to alkaline pH (baking soda, ammonia) → Darker black
- Soak powdered oak galls in ethanol (70%) for 24-48 hours.
- Filter the extract and add iron sulfate to develop the black color.
- Evaporate excess alcohol to concentrate the pigment.
Uses of Red Onion Skin Extract
- Ink Production – Traditional iron gall ink (historical manuscripts).
- Textile Dyeing – Wool, silk, and leather.
- Leather Tanning – Enhances durability and colorfastness.
Would you like details on industrial-scale processing for higher efficiency?
