Effect of Modified Rinsing Conditions on the Whiteness of Laboratory Scoured Wool

The effect of detergent distribution and the influence of various additives to the penultimate rinse bowl on the whiteness of laboratory scouted wool was investigated. With different distributions of scouring reagents (nonionic detergent plus alkali) between bowls 1 to 3 and a rinse in bowl 4, the whitest samples of both high yielding and low yielding merino fleece wools were obtained with the following bowl compositions: bowl 1, a large amount of detergent plus alkali; bowl 2, rinse; bowl 3, a small amount of detergent plus alkali; bowl 4, rinse. The lowest whiteness resulted when all the detergent was added to the first bowl. Intermediate whitenesses were obtained when a small amount of detergent plus alkali was followed by a large amount in the later bowls. In a more conventional scouring system with constant scouring conditions in bowls 1 and 2, the addition of various builders to bowl 3 increased the whiteness in the order sodium carbonate < trisodium citrate < trisodium ethylenediamine tetraacetate (EDTA-3) < trisodium nitrilotriacetate. Analyses of the level of residual contaminantes gave a statistically significant negative linear correlation between whiteness and residual iron content for both high and low yielding wool. For the low yielding wool, statistically significant correlations aiso existed between whiteness and residual solvent extractables, residual calcium, and ash content. The improved whiteness obtained using EDTA-3 compared with no additive was also observed initially in simulated continuous scouring, but the overall whiteness decreased rapidly thereafter because of the rapid build-up of contaminants in the liquor.