Vegetable Matter

As Australian wool is grown in a wide variety of environments, contamination by vegetable matter is largely dependent on the area of origin of the wool. Vegetable matter consists of burrs, grass seeds, thistles, hardheads, straw, chaff and small pieces of stick and bark. Particular plant species are suited to different environments and hence only contaminate wool grown where they are prevalent. The amount and type of vegetable matter in a lot of wool has implications for processing. Some types are easily removed and create no problems, others are broken up during carding and are difficult to remove, others form a matt of seeds in the wool, while others are so hard they may break machinery and/or cause problems in carbonising.

Vegetable matter base and vegetable matter content are both measured as part of the core test, which is conducted on early 100% of Australian wools. Vegetable matter base is the percentage dry material expressed as a percentage of the weight of the greasy core sample. During this test, the proportions of Burr (spiral burr, clover burr and other soft burrs), Seed (seed, shive and other small particles) and Hard Heads (hard heads and twigs) are determined. The AWEX ID system further categorises vegetable matter into seven categories, viz. Burr, Seed, Shive, Noogoora/Ring, Bathurst, Moit and Bogan Flea, which helps define their effects on processing.

Thus, through the core test, buyers have quantified information on both the amount and type of vegetable matter in a lot of wool. And, in the auction system, this objective information is supplemented by visual appraisal using the AWEX ID system. This allows buyers to make informed decisions when purchasing wools, thus appropriate price premiums and discounts can be applied for vegetable matter.

Man-Made Contaminants

Man-made contaminants which originate from farms in Australia include wool bales or packs and farm objects such as fertilizer bags, baling twine, pieces of metal or clothing.

Ten years ago, the HDPE farm pack, which does not take up any wool dye, was 4% of the total man-made contamination. However, today there is little to no contamination from this source. This is primarily due to the fact that Australian wool growers are now required by AWEX to use new packs made of nylon. Although contamination by nylon packs can occur, any large pieces are usually removed in the early stages of processing.

Of the other man-made contaminants, in 2003 hay-bale twine (61%), fertilizer bags (14%) and feathers (8%) were the most prevalent, making a total of 92% of all non-wool contaminants. Between 1993 and 2003, there was a general decline in the incidence of these forms of contamination. During this period, industry-wide communication programs alerted participants to the on-going problem of man-made contamination. While the problem has not been eliminated, the Australian wool industry continues to proactively address the issue.