As an IWTO certified test house, NZWTA provides the option of a Certificate or a Report for results of wool that we test. A certificate comes with guarantees and to achieve these guarantees, the whole process of sampling, processing and testing must be regulated to ensure result authenticity and integrity. NZWTA appoint, train and audit sites and sampling officers to oversee the process. Sampling of greasy wool can be manual or by machine. It is vital that a good representative sample is taken to provide an accurate result to the customer.

Once collected, samples are then packaged and sent to NZWTA for testing. On arrival in the lab, the sample is written up according to the required test. Several test types are available, the principle ones being:

• Yield, Colour, Micron on scoured and greasy wool
• Residual grease content and conditioned weight
• Length and Strength – commonly for fine wool, with increasing application in strong wool
• Length after carding – common for scoured wool

For all wool that requires Yield, Colour, Micron, Residual Grease and Conditioning, the first few steps follow similar paths. After the write up step, the process moves to Blending and Sub-Sampling – the homogenisation step.

For an accurate result, the wool sample must be well blended to ensure it is a good representation of the whole line or batch of wool. The sample is then sub-sampled, with one part following the Yield pathway, another following the Colour and Micron path, and a final sub-sample kept for any future check testing needs. The two sub-samples for testing then go through our mini scouring process, intended to replicate commercial scouring.

Several steps are involved in attaining the yield measurement. After sub-sampling, the wool is weighed and recorded. The sample is then scoured and dried in ovens at 105 degrees Celsius for about an hour. This results in the oven dry mass. After this process, the sample contains absolutely no water – only wool, some residual grease, the Vegetable Matter (VM) and a mineral component. All of these factors are key to unlocking the yield calculation.

Wool samples pass through a Near InfraRed Spectrometer (NIR). Calibrated accurately through thousands of samples, the NIR allows a much accelerated and efficient cost method, providing a reading of Ash (mineral content) and residual grease in the wool, post scouring.

Sub-samples are then prepared for Vegetable Matter quantification and calibration work, for both the Ash Content and Residual Grease. These factors are then fed into the appropriate yield calculation.

Wool for colour and micron testing is scoured, dried and then sent to the Shirley’s. Shirleying involves a machine that pulls the wool fibres apart in order to remove any final pieces of vegetable matter and open the fibres completely from one another. This allows a more accurate measurement of both colour and the micron.

Wool is conditioned, and then measured a minimum of four times using the colorimeters. The values of X, Y and Z are taken and often presented with the Y-Z value, as this is a key measurement for wool buyers contracts.

Micron measurements may be completed by Laser, Airflow, OFDA or Electron microscope. Commercially, Airflow is preferred for coarse wools and Laser is used for the fine wool sector. The video below explains both Laser and Airflow in detail.

Throughout the entire scouring process, three LAC test samples are randomly drawn using specially-designed sampling equipment. One of the three samples is randomly selected as the test sample. The sample is carded and gilled to remove the vegetable matter and align the fibres. Sliver samples are twisted into hanks in preparation for measurement. A series of fibre draws are prepared from the slivers and read on an almeter.

The LAC test provides a certified measurement of Barbe length for the scoured delivery. Additional data on Hauteur length and length distribution, and an estimate of the card waste (percentage) is also available.

Staple Length, Staple Strength and Position of Break are important measurements that assist in the prediction of processing performance. NZWTA test most of the Merino wool in New Zealand and have also developed the test to be applicable for crossbred wool.

The Length and Strength test begins with extensive sampling involving mechanical grab and tuft sampling equipment to obtain a representative specimen. The samples are prepared and conditioned before being tested by NZWTA using the industry-leading ATLAS (Automatic Tester of Length And Strength) instruments. Samples are tested with a minimum of four instruments, used to test at least 60 staples, for the certification of each sale lot.

All certified results will be presented to the buyer as an IWTO Certificate. If the sampling was not conducted by a registered sampler, then results can only be provided as a report. This is due to the lack of  chain of custody or independence in the sampling process.