Dung-stain (penstain) of wool and its effect on dyed colour and photofading

Abstract

Abstract Wool samples were collected from 40 7-month-old sheep, before, immediately after, and 7 days after exposure to conditions likely to lead to penstain. The reflectances of red (X), green (Y), and blue (Z) light were measured in the greasy, scoured, clean, felted, and dyed states. To check whether penstain contributes to photofade, reflectance changes in felted and dyed samples exposed to sunlight were assessed. Groups were made according to the degree of visual yellowness of the fleeces and whether some sheep in the group had lumps of dung (dags) suspended on the wool around the anus. Greasy wool samples selected as being penstained after the sheep had been exposed to penstaining conditions, had much reduced tristimulus colorimeter reflectances compared with nonpenstained samples. The reduction was much less marked after scouring. After dyeing there were still effects that were statistically significant although they may be too small to be commercially significant. Samples taken at random after pen...