A wool or hair top produced by adding 3% extra oil above the dry-combed top standard to give a total fatty matter content of 3.5% when calculated by the traditional Bradford Method.
On the International Wool Textile Organisation’s method of testing the maximum fatty matter content becomes 4.6% based on the oven-dry fat-free weight. This method specifies Soxhlet extraction with dichloromethane as the solvent.
Note 1: The standard regain of an oil-combed top is 19% based on the combined weight of oven-dry fat-free wool and the fatty matter.
Note 2: A top that has been dry-combed and subsequently oiled is also described as an oil-combed top
Textile Resource (http://www.textile.org.uk)