1 — Fiber
2 — Mordant
Tannin pre-mordant
Optional additives
3 — Dye
Water volume
Your Recipe
Fill in your fiber details to see your recipe.
Enter your dry fiber weight to get a complete recipe — mordant, tannin, dye, and additives — calculated by Weight of Fiber (WOF).
All natural dye measurements use Weight of Fiber (WOF) — the dry weight of the material to be dyed — as the base unit. Mordant, dye, and additive quantities are then stated as a percentage of that weight. This system scales seamlessly: a recipe that works for 100 g works just as well for 1 kg, with quantities simply multiplied by ten.
Amount of ingredient (g) = Dry fiber weight (g) × %WOF ÷ 100Always weigh fiber dry, before scouring. The WOF is locked in at that number and does not change as the process proceeds.
The most widely used natural dye mordant. Safe, inexpensive, and produces clear, bright colors on both protein and (with tannin) cellulose fibers. The standard rate of 15% WOF applies to most protein fibers. Above 20% WOF the fiber can become sticky.
Preferred for cellulose fibers — cotton, linen, hemp — as it bonds more readily without requiring a heavy tannin pre-treatment. Produces richer color development than alum sulfate on plant fibers. Often combined with a chalking step (chalk at 2% WOF in the rinse) to fix the mordant.
Cellulose fibers need a tannin mordant bath before alum, because alum does not bond as readily to plant fiber as to protein. Tannins naturally present in some dye plants (walnut, sumac, cutch) can serve a dual purpose as tannin and dye. Clear tannins (oak gall / gallo, myrobalan) are used when you want the tannin step not to color the yarn.
A color modifier rather than a primary mordant. Iron "saddens" colors — deepening yellows toward green, reds toward brown, purples toward black. Used at 2–4% WOF maximum; exceeding 4% WOF can damage fiber, particularly wool. Most often added as a post-mordant near the end of the dyebath.
An optional softener and color brightener added to the alum mordant bath for protein fibers. Keeps wool supple and can shift cochineal toward a truer red. Do not use on cellulose fibers.
The following rates are general guidelines from practitioner sources. Always perform a test skein first, as exact shade depends on fiber, mordant, water pH, and heat.
The liquor ratio is the ratio of water to fiber by weight. A liquor ratio of 30:1 means 30 liters of water per 1 kg of dry fiber (or 30 mL per gram). This is the most widely cited starting point among natural dye practitioners and gives fiber enough room to move freely and absorb mordant or dye evenly. Using more water is fine; using less can cause patchy, uneven uptake.
For small batches (under 50 g), a ratio of 20–30:1 is practical. For large commercial batches you may reduce the ratio slightly to save energy, but 20:1 is typically the minimum for even results.
What does WOF mean in natural dyeing?
WOF stands for Weight of Fiber — the dry weight of the material you plan to dye. All mordant and dye quantities in natural dyeing are expressed as a percentage of this figure. For example, 15% WOF alum on 100 g of wool means you use 15 g of alum. Always weigh fiber dry, before scouring or wetting.
How much alum do I use for natural dyeing?
The standard rate for potassium aluminum sulfate (alum) is 15% WOF for protein fibers such as wool and silk. For cellulose fibers like cotton and linen, alum is applied after a tannin pre-mordant, also at 15% WOF. Aluminum acetate, an alternative cellulose mordant, is used at 5–8% WOF. Exceeding 20% WOF can make wool feel sticky or tacky.
Do I need tannin before alum on cotton?
Yes. Cellulose fibers like cotton, linen, and hemp require a tannin pre-mordant before alum because alum does not bond as readily to plant fibers. The tannin bath (8% WOF is a common starting point) must be completed first, then the alum bath follows. Alternatively, aluminum acetate can be used without a separate tannin pre-mordant on many cellulose fibers.
What does iron do in natural dyeing?
Iron (ferrous sulfate) is a modifier that "saddens" or deepens colors — shifting yellows toward green, reds toward brown or grey, and purples toward near-black. It is used at 2–4% WOF. Exceeding 4% WOF can damage or harden fiber, especially wool. Iron is most commonly added near the end of the dyebath as a post-mordant.
What is cream of tartar used for in mordanting?
Cream of tartar (potassium bitartrate) is an optional additive used at 5–6% WOF in the alum mordant bath for wool and silk. It helps keep protein fibers soft and supple, brightens some colors, and can shift cochineal reds toward a truer red. It should not be used on cellulose fibers such as cotton or linen.
How much water do I need in a mordant or dye bath?
A common guideline is a liquor ratio of 30:1, meaning 30 liters of water per 1 kg of dry fiber (30 mL per gram). This allows fiber to move freely and absorb mordant or dye evenly. You can use more water without affecting results, but using too little causes uneven uptake. The calculator defaults to 30:1 and lets you adjust.
Can I reuse a mordant bath?
Yes, mordant baths can often be reused. Research by natural dye educators has shown that a significant proportion of alum remains in the bath after one use. You can top up with roughly 50% of the original alum quantity before the next batch. Keep careful notes of what went into the bath so you can calculate carry-over accurately.
Why isn't indigo included in the dye calculator?
Indigo (and woad, when used as a vat dye) is a substantive dye that does not use the WOF percentage system in the same way as other natural dyes. Indigo is applied through a reduction vat process and does not require mordanting. It would need its own specialized calculator. This tool covers the mordant + dye recipe workflow for all other common natural dyes.