Introduction

Classical denim is a heavy fabric made from 100 per cent cotton and woven from coarse indigo dyed warp and grey undyed weft yarn. It has hard-wearing, high density fabrics with a high mass per unit area and a 3/1 or 2/1 twill weave construction. Denim is available in attractive indigo blue shades and is made for a variety of applications and in a wide range of qualities and shades. Besides indigo blue, denim is also dyed in other fashion shades and colors, the most popular being black. Denim is comfortable, fashionable, affordable and durable and popular in all age groups. It is available in different weight ranges from 6-16 oz/sq yd which is categorised as light denim 10-12 oz/sq yd., heavy denim 14-16 oz/sq. yd.

Excel, a commercial name of lyocell fibre produced by Birla Cellulose of the Aditya Birla Group, is the latest man-made cellulose fibre. The raw material used to make lyocell fibre is wood pulp. This is sourced from harvested trees and is, therefore, a renewable resource.A solvent is used to dissolve the cellulose directly into a very viscous solution. After filtration, the solution is extruded to yield fine filaments, from which the solvent is subsequently removed by washing.

The resulting tow is dried and cut to staple fibre. A key feature of the process is that virtually all of the solvent is recovered and recycled. Thus, the effluent from the process is minimal and most importantly, its not classified as hazardous. Lyocell, as a cellulosic fibre, absorbs moisture and is fully biodegradable. It is characterized by its high strength both dry and wet. It shows a dry tenacity significantly higher than other cellulosics and close to that of polyester.

Lyocell fibre has exceptional attributes like extreme strength, high moisture absorbency, skin- friendliness, excellent lusture and high colour depth, fibrillation and seude effect, unique drape and fluidity, high dimensional stability and wash and wear characteristics.

Due to these attributes, lyocell denims are very popular nowadays and thus bulk manufacturing is rising.

Denim has been used as a clothing material for centuries due to its high durability. But today'sfashion arena likes denim jeans due to its attractive shades, designs, styles and various types of wash appeal, rather than for its robustness. Denim jeans in the past were worn in a raw, rigid and starch-finished form. But today's fashion requires various types of washing treatments, such as desizing, enzymatic washing with or without stones, decolorization, neutralization, brightening and finishing.

Normally denim washing is carried out in sewn garments. The denim jeans are subjected to different washing techniques, such as rinsewash, bleach, enzyme wash, acid wash, stonewash, moonwash, sandwash, sun wash, overdyed/ tinted look, whiskering, damaged and used look. In denim washing, enzymes played an important role to get clean, smooth, fuzz free fabric surface with reduced tendency of pill formation and improved fabric handle.

Raw denim jeans show natural shade of indigo that is faded during wear and subsequent

washes at home. However, in some cases it is believed that raw denim is not practical as it creates some problems of rub-off on other materials that come into contact with it. The unfixed dye on the surface of the fabric may cause stains to other fabrics.

To overcome this problem, denim jeans are washed after sewn. The main plus point of prewashing of denim jeans is that the colour is not transferred to other fabrics or surfaces during wear.