A wool top containing not more than 1 % of fatty matter based on the oven-dry, fat-free weight as tested by the International Wool Textile Organisation’s method which specifies Soxhlet extraction with dichloromethane
Note: The standard regain of a dry-combed top is 18.25% based on the combined weight of oven-dry, fat-free wool and the fatty matter.
Textile Resource (http://www.textile.org.uk)