How does wool scouring differ from cotton scouring?

First point to be noted that, wool is having very high amount of waxy matter than cotton. The wax matter of cotton is removed by treating cotton with sodium hydroxide solution at boiling temperature. But sodium hydroxide solution can not be used for scouring of wool as wool is very sensitive to alkali. Therefore wool scouring is carried out with detergent or mild alkali like sodium carbonate solution (pH around 8 to 10). 

There are three methods for wool scouring:

i) Emulsion scouring: In this method the raw wool is scoured in a tank filled with detergent having pH 8-10. In the process temperature is maintained around 55-60 degree C and time duration 30-45 minutes. After that wool is washed and dried.

ii) Solvent scouring: In this type of scouring raw wool is treated with solvents like Trichloroethylene, perchloroethylene or carbon tetra chloride (now it is banned in India). These solvent remove wax from the wool. This wax and solvent is recovered. The recovered wax are used various application.

iii) Freezing: As its name suggest, wool is subjected to very low temperature about -30 degree C. Due to this wool wax becomes hard. At same low temperature is is mechanically crushed followed by shaking. Wax is removed.