Bulk Tests

Bulk is the ability of a fibre assembly to hold air, or its space-filling capability. Wools destined for products in which bulk is important, such as carpet yarns, hand knitting yarns, and wools going into filling, may be certified for bulk using NZ 8716.

The test method requires that the core samples be scoured, dried, opened, and conditioned under very carefully-controlled conditions. From the opened samples, quadruplicate test specimens of precise mass are put through a specified load cycling process before the bulk (in cubic cm per gram) is measured in the WRONZ autobulkometer (see Info-bulletin 5.1 ).

Detailed investigations into alternative methods have been carried out at the Wool Research Organisation of New Zealand (WRONZ) and elsewhere following our initiative to use the OFDA to predict bulk (see Info-bulletin 3.2 ). A bulk prediction algorithm has now been incorporated into the software of OFDA2000 instruments in use in New Zealand, which allows the on-farm selection of crossbred fleeces and animals for this important parameter. Details of investigations into alternative prediction algorithms for use with the OFDA instruments are given in technical publication M24.