Mineral dirt includes wind-blown material or material picked up when the sheep lie on the ground. Mineral dirt is, in most part, not soluble in water, but soluble components can leach into the scouring liquor and affect the scouring practice. This is by increasing the hardness of the water, or by increasing the concentrations of metal ions, such as iron that cause re-deposition and adversely affect the colour of the scoured wool.tains the highest quality and most valuable wool.

 

Vegetable matter includes seeds, burrs and twigs that attach to the fleece while sheep are grazing or lying down. Vegetable matter (VM) is usually removed from a fleece during skirting. Long, thin pieces of vegetable matter can behave like wool fibres during processing and are difficult to separate from the wool fibres. Natural dyes that are present in the fleece have the potential to stain the wool fibres during scouring. The brittle pieces of vegetable matter can break up in the fleece, creating further contamination.

 

Fecal matter and urine are bodily excretions that can attach to the localised parts of the fleece. Faecal matter or ‘dags’ appear mainly in pieces and crutchings. They are more likely to present problems when processing wools destined for the woollen processing route. Urine stains cannot be removed entirely by scouring. Stained processing lots are usually cheaper. It is common practice to blend stained lots with more expensive, unstained lots. When scouring urine-stained wool, its end use should be kept in mind; a scoured wool that is too yellow cannot be used for products in which pastel shades are used to dye the wool.