High humidity throughout the country has degraded wool colour, which will impact on grower returns. 

Chief Executive of the New Zealand Wool Testing Authority (NZWTA) Duane Knowles says humidity has been elevated over the past two seasons.

“Because wool is a biological product, it will degrade with humidity, turning it from white to yellow, and making it less desirable for dying. This occurs before and after shearing, so also impacts on wool held in storage. 

“Two seasons ago, the 2016/17 summer was the most recent ‘normal’ year for wool colour. NZWTA statistics measuring colour show this year and last, wool was typically over a unit higher in colour than in that year. Increased degradation was consistent for North and South Island wool,” he said.

In the dying process whiter wool is better able to take pastel shades, therefore commands a higher price. Yellow or creamy wool, with higher colour measurements, can only take dark colour dyes, which limits its use among spinners, dyers and manufacturers.

As New Zealand produces the world’s whitest, brightest coarse wool, in normal circumstances it attracts a premium. However, when colour is high it can be substituted with wool from elsewhere, reducing demand and lowering market prices.

Optimising colour is difficult, says Duane.

“Although growers have little control over humidity, they can control decisions around shearing times and patterns. The longer wool is left on the sheep, the yellower it becomes; and the longer it is stored before sale, the more it degrades. Shearing on a six or eight month cycle is therefore preferable to a 12 month shearing pattern, and minimal storage will also ensure optimum colour,” he said.

Test certificates for colour are only valid for six months. If wool is held for longer, a new test will have to be run.