UJJAPPA · DMI-OS

Enter the dry weight of your fibre and the mordant you plan to use. The calculator gives you the exact grams to weigh out.

Fibre type

Weight of fibre (dry, grams)

Mordant

Most common mordant. Safe, good colour, works on all fibres.

Mordant % WOF

% of fibre weight

Add cream of tartar (6% WOF) — brightens colour, protects wool

Results for 100g of Wool

Alum (Potassium Aluminium Sulphate) at 15% WOF

Alum (Potassium Aluminium Sulphate)15.0 g

Water (mordant bath)3.0 L

Dissolve mordant in hot water, add to bath, enter pre-wetted fibre, heat slowly to 82°C, hold 45–60 min, cool slowly before removing.

Quick reference

Mordant	Fibre	% WOF	Notes
Alum	Wool	15%	Standard, reliable
Alum	Silk	10%	Less to protect fibre
Alum	Cotton	15% + tannin pre-bath	Tannin first
Iron	All fibres	2–4%	Use sparingly
Copper	Wool/Silk	2%	Ventilate well
Tannin	Cotton/Linen	8%	Pre-mordant only