Mordants for setting the colours from natural dyes.
Mordants form a chemical bond with fibres, creating attachment points for the colourants extracted from natural dyes. They improve light and wash fastness, and different mordants can modify colours by brightening, tinting or saddening shades. Mordants are also used to help set colours from flowers and leaves during the process of Botanical Eco Printing.
Textiles can be pre-soaked in a mordant solution and left damp before dyeing, or the mordant can be added directly to the dye bath while the dye is being simmered. Mordanting fibres before dyeing improves fastness, while Copper, Tin and Iron can be used as after-treatments to adjust and modify colours.
Alum is the most widely used mordant for natural dyeing because it improves colour fastness without significantly altering the shade. It forms a chemical bond with the fibre, allowing the colourants from natural dyes to attach and produce colours that are more resistant to washing and fading.
The process of mordanting cotton, linen and other cellulose fibres differs from that used for wool and silk. Cellulose fibres must first be treated with tannin, which provides sites for the mordant to attach to. Most tannins impart some colour and may influence the final shade, which is often a desirable effect. Where it is important to retain the natural colour of the fibre, Aluminium Lactate can be used as an alternative mordant for cellulose fibres.
Sources of tannin can be found in our Natural Dyes and Natural Dye Extracts category. Additional products for modifying colours can be found in Dye Assistants, Modifiers & Mediums.
Mordants for Natural Dyeing
Mordants for Botanical Printing
Auxiliaries for Botanical Printing
Discharge Dyeing
Sensible precautions must be taken when handling dyes and chemicals, particularly as powders:
- Avoid inhaling dusts, they can produce an asthma type reaction. People with known respiratory problems should not handle synthetic dyes, and particularly the fibre reactive dyes, in powder form. A dust mask should be worn when working with the powders or exposed to an aerosol from spraying dye solutions made up in water.
- Avoid splashing solutions into the eyes, swallowing the materials or prolonged skin contact. A simple 'non-contact' approach (most people use gloves to avoid dyeing themselves) plus normal, good, hygiene is sufficient precautions for the occasional user.
- Store in clearly labelled containers well away from children, pets and foodstuffs. Treat dye powders and solutions with the same caution as domestic poisons (e.g. strong cleaners, bleaches or medicines).
- Dispose of spent solutions containing residues of the dyes responsibly. Dilute and pour onto waste land or into the sewage system. They have no known effect on the environment when used in the quantities recommended in the literature.