Mercerising Machines:

Why Mercerising?

John Mercer's finding established the process of Mercerising as a very useful and versatile treatment, as far as cotton materials are concerned. Whichever Mercerising unit may be used for cotton in whatever form, the following results can be obtained by a controlled action of caustic soda lye.

Increase in tensile strength
Increase in lustre
Soft silky feel
Increased affinity for dyes
Increased power of responding to mechanical finishing processes, such as calendaring, shearing, frictioning, etc.

A precautionary measure is mercerising is that, during the removal of the mercerising lye by washing, the tension on the textile material should be maintained, as otherwise dimensional shrinkage will result.

http://www.kusterscalico.com/products/mercerising/merdet.htm