Two important mercerizing processes, these are:

i) Slack Mercerization

ii) Hot Mercerization

i) Slack Mercerization:  The slack mercerizing is a process in which good moisture absorption, good dye uptake and stretchability (ability to extend and recover after extension) is required but strength and lustre is not so important. The slack mercerizing can be carried out for the products like bandages, casual wear, skirts, boat covers etc.  In this process, cotton fabrics are allowed to shrink without tension in a solution of caustic soda (25 to 30%) at around 30 degree Celsius for 60 seconds. The fibres during then, shrinks to a level of 15 to 19% accompanied by considerable lateral swelling of fibres in the yarn. Following three changes take place in the slack mercerizing:

a) An increase in diameter due to permanent swelling

b) A decrease in length i.e shrinkage

c) An increase in the atmospheres volume at the loss of crystalline region.

How do you carry out Slack Mercerizing:

If slack mercerization is to be carried out continously then J-Box can be used. The J-Box consists of caustic soda liquid (23%) within which the fabric is plated and remains for 5 minutes. It then passes through a nip followed by a series of was boxes (Open Soaper) and then cylinder or stenter for drying purpose. Nipping is done very near to the places where the fabric just comes out of the J-Box in order to reduce the tension. Open soaper are used for washing and souring in which the bottom rollers are over driven to reduce the tension.