A dye is a coloured compound that dissolves in water and bonds to a fibre, while a pigment is an insoluble coloured particle that sits in a binder; dyes colour cloth, pigments colour paint and ink. Most plant dyes wash out unless the cloth is first treated with a metal salt called a mordant, and indigo, a vat dye, is the main exception. Colour is mostly a matter of choosing the right source and fixing it properly.
Part of Organic Chemistry
The sources of colour from plants, insects and minerals, and the difference between dissolving a colour into cloth and suspending it in a binder.
Dye Versus Pigment Decides How You Use A Colour
A dye is carried into the fibre by water and held there by chemical bonding, which is why it can be fixed (mordanted) or washed out. A pigment is a finely ground solid that does not dissolve; it must be mixed with a binder such as gum, oil or egg to stay put. Earth pigments, soot and mineral colours are pigments; indigo, madder and weld are dyes. Dyes appear under the carrier’s heading “Dyes and Pigments” as a practical subject: the carrier says colour enables identification, record-keeping with coloured inks, and trade goods, since dyed fabric is more valuable than undyed.
The Carrier’s Source Table In Brief
The carrier gives seven colours with a source, an extraction route and a mordant need: blue from indigo or woad by fermentation and oxidation (no mordant, a vat dye); red from madder root boiled with alum; yellow from weld, onion skins or turmeric simmered with alum; brown from walnut hulls or oak bark with optional mordant; black from oak galls and iron, where iron is itself the mordant; green by overdyeing indigo with weld; and purple from elderberry or blackberry with alum and cream of tartar. Colour-specific articles in the corpus: Blue Dyes, Red Dyes, Yellow Dyes, Brown and Black Dyes, and the overview Natural Dyes and Inks.
What You Need
- Dye plants or materials, identified and collected in quantity (see Dye Sources).
- A mordant, usually alum (Mordanting).
- Non-reactive pots (enamel, stainless, or a pot kept only for dye).
- Clean fibre, scoured of oil and dirt first (Fiber Preparation).
- Plant dyeing guidance: Plant Dyes and Dyeing Process.
Method: The Order Of Operations
Step 1: Scour the fibre.
Step 2: Mordant it, unless using a vat dye.
Step 3: Dye in a bath held below boiling for the time the colour article gives.
Step 4: Rinse, dry and test fastness by washing a swatch (Fastness Testing).
Worked Example: Weighing A Dye Batch
Dye quantities are set as a percentage of the dry weight of fibre. For 500 g of dry cloth, a bath using an illustrative 100% of the cloth weight in dye plant uses 500 g of plant, and the carrier’s 15-20% alum mordant is 0.15 × 500 = 75 g to 0.20 × 500 = 100 g. The percentage rule means the recipe scales to any batch without a new recipe. Which percentage of dye plant to use for a given colour comes from the colour articles, not from this page.
Common Mistakes
- Skipping the mordant on madder or weld, which then wash out after the first rinse.
- Dyeing unscoured cloth, which takes colour unevenly.
- Using a food pot, since some mordants and dyes are toxic.
- Judging colour while wet. It dries lighter.
Safety
The bath is hot, and some mordants and plant dyes are toxic
Hot dye baths scald. Alum is mild, but iron liquors and some metal mordants are not, and many dye plants are irritants. Keep dye pots and utensils separate from food gear, ventilate steam, and do not drain spent metal-salt baths into a well or stream; see Waste Treatment.
What’s Next
- Learn next: Mordanting — fixing the colour
- Combine with: Ink Production — colour made into a writing material