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Chemical Treatment - In Scoured Wool


Scouring wool can often involve a number of chemical treatments in order to standardise its colour or provide additional properties to improve its intended product-use.

Tests for damage are based around the principle that wool shows an increased solubility in alkaline solutions when attacked by oxidising or reducing agents, acids, or exposure to heat or light. Most testing on scoured wool is conducted to quantify the damage caused by hydrogen peroxide bleaching, a chemical regularly used to produce a whiter visual appearance for the wool.

The Alkali Solubility Standard: This test is conducted according to test method IWTO DTM-4. It involves the treatment of a dry wool sample in sodium hydroxide under controlled conditions of time, temperature and volume. The alkali solubility is calculated as the loss of the mass of the treated specimen expressed as a percentage of its oven dry mass.

The results reported are:

(a)     The pH of the aqueous extract

(b)     The individual alkali solubility for each specimen and the mean result for the sample

The test is most useful when an untreated control sample is available and when the nature of the treatment of the sample under test is known. The test does not provide an absolute measure of damage, instead is useful as an indicator of relative levels of damage.

Download - Fact Sheet: The Alkali Solubility TestPDF

For more information.....on Alkali Solubility testing, contact NZWTA on +64 6 835 1086 or email us at