Chemicals in Wool Processing: What You Need to Know
Much of wool processing is mechanical rather than chemical. Where chemicals are used, the wool industry applies them carefully, and has phased out chemicals of concern in compliance with European REACH regulations.
The stages below follow wool from the farm through to finished fabric, noting where chemicals play a role and what they are.
On Farm
Veterinary-registered medication may be administered to sheep for the treatment of external and internal parasites, either as a spray or oral application.
A 2022 study of greasy wool from Australia and New Zealand — together accounting for almost a third of global wool supply — confirmed a low incidence of residues well within EU limits, with a decreasing trend: some residues have now reached an average of virtually zero.
Early Stage Processing: Cleaning
Scouring Raw wool is washed using warm water and non-ionic detergents. These do not contain alkylphenol ethoxylates.
Carbonising For shorter wools that cannot be combed, vegetable matter is removed using a bath of dilute sulphuric acid, followed by soda ash and hydrogen peroxide — all common chemicals.
Subsequent Processing
Mechanical processes
The following stages require little or no chemical input:
- Carding, gilling and combing — these mechanical processes use lubricants to reduce friction between fibres as they are processed, with very little water required.
- Drafting — a mechanical process in which a thick strand of fibres is drawn down to a finer one. No chemicals are used.
- Spinning and twisting — both involve mechanically twisting a strand of wool. No chemicals are used.
Finishing processes
- Dyeing — wool can be dyed at the fibre, yarn, fabric, or garment stage. The process uses acetic acid, levelling agents, and synthetic dyestuffs; chromium-based mordants are not required to fix colour to the fibre.
- Softening — wool products are softened using a wax- or silicone-based softener.
- Shrink-resist treatment — some wool tops are treated to allow machine washing. The most common process has two stages: first, an oxidising agent lightly etches the surface of the wool fibre; then a small amount of Hercosett resin is applied. The Hercosett forms a swellable matrix on the fibre surface that masks the scales and prevents shrinkage during washing. Research confirms that machine-washable wool still biodegrades in both soil and water, and that machine-washable wool does not contribute to microplastic pollution.
- Alternative shrink-resist treatments — for some yarn types, the oxidising stage can be replaced with a plasma-based process, which uses fewer chemicals and less water.
- Flame retardancy — wool is inherently flame-retardant. In specific high-risk applications, an additional treatment using a zirconium-based flame retardant may be applied.
- Water and stain repellence — wool is naturally water- and stain-repellent. Where higher levels of repellence are required, a silicone- or wax-based treatment can be applied during finishing.
Want to go deeper? This page is drawn from Wool Notes, IWTO’s comprehensive guide to wool from farm to fabric. Download your free copy for the full picture.