AWTA Ltd Certificates and Reports

Yield, VM and Fibre Diameter

IWTO Test Certificates for commercial yield must show the Wool Base (WB) and the Vegetable Matter Base (VMB) (including % Hard Heads and Twigs (HH)) as well as the particular commercial yield calculation relevant to the wool trading negotiation. Unless a particular commercial yield basis is requested, the AWTA Ltd Certificate will include the 4 commercial yields that appear in the auction sale catalogues:

IWTO Schlumberger Dry Top & Noil Yield (1%TFM)

IWTO Schlumberger Dry Top & Noil Yield (1%TFM) is the most commonly used commercial core test yield and predicts the amount of Top and Noil that can be combed from the greasy wool. It is the main yield basis for wools traded in Western Europe.

An allowance of 2.27% is made for residual ash and grease, 18.25% moisture regain is added to the Top and 16% moisture regain is added to the Noil. The Total Fatty Matter content (TFM) is 1% and a tear ratio (the conditioned weight of Top to the conditioned weight of Noil) of 8:1 is assumed. The conversion factor of 1.207 applied to WB takes account of these factors.

The yield includes an allowance (Processing Allowance) for fibres lost during processing. This fibre loss is directly related to the VMB minus the HH and is calculated according to the following formula:

IWTO Scoured Yield, 17% regain

IWTO Scoured Yield, 17% regain is calculated from WB and VMB. An allowance of 2.27% is made for residual ash and grease and 17% moisture regain is included. This yield estimates the “washing yield”, i.e. the yield of product obtained after scouring but before any processing occurs to remove VM. It is commonly used in trade with Eastern Europe.

SCD 17% = (WB + VMB) x 1.1972

While not shown in the catalogue, an IWTO Scoured Yield, 16% regain is commonly used in trade with China.

Japanese Clean Scoured Yield

Japanese Clean Scoured Yield is the normal basis for trade with Japan. An allowance of 1.5% is made for residual ash and grease, and 16% moisture regain is included. Although this yield has the VM deducted, no allowance is made for fibre loss that could occur during processing.

JCSY = WB x 1.1777

Australian Carbonising Yield

Australian Carbonising Yield is popular in Australia, Japan, Korea and Europe as the basis of trade in carbonising and carding types (lox, crutchings, lambs etc.). An allowance of 2.27% is made for residual ash and grease and 17% moisture regain is included. The yield calculation for WB and VMB allows for expected processing losses during carbonising.

ACY = (WB x 1.1972) + (VMB x 0.162) - 5.12

Fibre Diameter

The AWTA Ltd Certificate normally includes Fibre Diameter results with the commercial Yield results. Consequently, the Certificate will also show Mean Fibre Diameter and Coefficient of Variation of Mean Fibre Diameter as measured by Laserscan. There is also a separate page of the Certificate repeating the Diameter results and showing a Histogram Graph of the fibre diameter distribution.

Staple Length & Strength

IWTO Staple Test Certificates must show the Mean Staple Length, Coefficient of Variation of Staple Length, Mean Staple Strength and the Percentage of Breaks in the Tip, Middle and Base regions of the staples.

Colour

The AWTA Ltd Colour Certificate shows the 3 tristimulus values X, Y and Z for the 2 methods that can be used to measure colour, and the important Y-Z value. The D65/10 measure is the result recognised by IWTO since January 2001.

Actual AWTA Ltd Certificates are shown below.

IWTO TEST CERTIFICATE

IWTO TEST CERTIFICATE (CONTINUED)

COLOUR TEST CERTIFICATE

IWTO STAPLE TEST CERTIFICATE