---
title: "Natural Dye Calculator: WOF & Mordants | Wild Linen Lab"
description: "Weigh your wool, silk or cotton and get alum, cream of tartar, tannin or aluminium acetate, dyestuff and water amounts from published % WOF figures."
url: https://wildlinenlab.cfd/natural-dye-calculator/
---

Entry 03 · natural dyeing

# Natural dye calculator

Enter the dry weight of your fibre, pick the fibre, mordant and dyestuff, and get every amount in grams and ounces, bath by bath.

## How the calculator works

Natural dyers measure everything as a percentage of the **weight of fibre** (% WOF): the dry weight of the yarn or cloth before it is scoured or wetted. At 15% WOF, 100 g of wool needs 15 g of alum. Weigh the fibre dry, enter it in grams, ounces or pounds, and every amount follows from that one number.

**Choosing a mordant.** A mordant helps the colour bond to the fibre. For wool and silk the calculator uses Maiwa's alum mordant: alum at 15% WOF with optional cream of tartar at 6%, heated to 90 °C for wool or 85 °C for silk. For cotton and linen, choose aluminium acetate (8% WOF, in hot water, then a chalk or wheat-bran fixing bath) or a tannin bath followed by alum with soda ash. Open "Adjust the mordant and water" to use a recipe's own figures.

**Choosing the dye amount.** Each dyestuff starts at the middle of Maiwa's range for a medium depth of shade. Lower it for paler colours and raise it for deeper ones; the calculator warns when you go outside the published range or need less than a gram.

**Worked example.** 100 g of wool yarn, alum mordant, madder root at 50% WOF: dissolve 15 g of alum and 6 g of cream of tartar in about 3 litres of water, mordant the scoured yarn, then dye it with 50 g of ground madder in fresh water.

## Sources

- Maiwa Guide to Natural Dyes: [How to mordant protein fibres](https://naturaldyes.ca/how-to-mordant-protein) (alum 15%, cream of tartar 6%, 30:1 water, temperatures) and [How to mordant cellulose fibres](https://naturaldyes.ca/how-to-mordant-cellulose) (aluminium acetate 8%, chalk and bran baths, alum 15% with soda ash 2%, the second alum bath for linen).
- Maiwa dyestuff pages, each giving % WOF for a medium shade: [madder](https://naturaldyes.ca/madder), [weld](https://naturaldyes.ca/weld), [cochineal](https://naturaldyes.ca/cochineal), [logwood](https://naturaldyes.ca/logwood), [onion skins](https://naturaldyes.ca/onion-skins), [marigold](https://naturaldyes.ca/marigold), [osage orange](https://naturaldyes.ca/osage), [walnut](https://naturaldyes.ca/walnut); and tannins: [gallnut](https://naturaldyes.ca/gallnut), [tara](https://naturaldyes.ca/tara), [myrobalan](https://naturaldyes.ca/myrobalan).
- Other published figures, for comparison: Earth Guild, [Mordants](https://www.earthguild.com/products/riff/rmordant.htm), suggests three ounces of alum and one of cream of tartar per pound of wool (about 19% and 6% WOF); Dharma Trading lists [aluminium acetate](https://www.dharmatrading.com/products/dharma-natural-dye-aluminum-acetate) at about 5–10% WOF.
- Safety: Maiwa, [Before beginning](https://naturaldyes.ca/before-beginning) (separate dye equipment, gloves, a mask for powders), and Washington State Department of Health, [Textile arts hazards](https://doh.wa.gov/community-and-environment/contaminants/art-hazards/textiles) (dust masks, ventilation, chemical-resistant gloves).

## Questions

**What does % WOF mean?**

Percent of the weight of fibre. It ties every amount to the dry weight of what you are dyeing, so a recipe scales to any batch: 8% WOF is 8 g for 100 g of fibre and 40 g for 500 g. The amount of water doesn't come into it.

**Should I weigh the fibre wet or dry?**

Dry, before scouring or soaking. Wet fibre holds a lot of water, which would make every amount far too high. Weigh skeins or fabric on a kitchen scale, and use a small jewellery scale for extracts and cochineal, where a recipe can call for less than a gram.

**Do I need cream of tartar?**

Maiwa lists it as optional for alum on wool and silk, at 6% WOF, and notes that it shifts cochineal from pink towards red. Set it to 0 under "Adjust the mordant and water" to leave it out.

**How do I get a paler or a deeper colour?**

The starting figures are Maiwa's ranges for a medium depth of shade. Use less dyestuff for pastels and more for deeper colours, and keep notes: the same percentages give the same result next time, whatever the batch size.

**Can I use my kitchen pans?**

Only if they never go back to the kitchen. Maiwa's advice is to keep pots and utensils for dyeing completely separate from those used for cooking. Stainless steel or enamel pots from a charity shop work well.