DENIM Finishing

& Washing

D. Praveen Nagarajan

STONE WASH

* Most denims are stone washed. When wash technique was developed,

denims were washed with actual stones but research and development has changed the whole scenario.Now-a-days pumice stones are used to achieve soft as well as desirable look. Many types of man-made stones, of different shapes and sizes are available in the market. Though they are expensive they provide more consistent quality of denim.

STONE WASH

Pumice stones are available in different sizes and shapes. Selection of pumice stone depends upon end products e.g.,

large and hard tones for heavy weight denimsmaller and softer stones for light weight denim

Recommended stone to fabric weight ratio is 0.5-3:1

Stone weight 0.5 to 3---------------- = ----------Fabric weight 1

Stone to fabric weight ratio depends upon the degree of abrasion desired in the in the washed denim.Stone wash cycle consists of several stages

STONE WASH

BACK STAINING AND COLOUR REDEPOSITION:

Back Staining and colour redeposition can pose a problem and could be reduced by:

* Addition of dispersing agent to wash cycle* Intermediate replacement of wash liquor for

example stone wash for 30 minutes, drop, Rinse, then again additional stone wash for 20 minutes, drop, rinse etc.

* Use of an alkaline detergent such as sodium perborate with an optical brighter as an after- wash

Stone Wash Cycle

Loading of denim garment and stonesDesizing for about 15 minutes- Detergent plus enzymes, or - Oxidative desizeRinsing Stone wash- 30 to 60 minRinsingSofteningExtractionUnloading and removal of stones from garmentTumble drying

DISADVANTAGES OF STONE WASHING

* Increased work of removing stone dust from finished garment after washing is completed

* Quality of abrasion process is difficult to control everything during washing gets abraded, including the metal buttons, rivets, drums of machine and the garment itself, which causes reduction in life of the washing machine as well as garments.

* Problem of water pollution due to presence of stone dust and treating the waste water and disposing of the sludge.

ENZYME WASH

In enzymes washing, cellulose* enzymes (a protein – like substance) are used.

Since colour in the denim fabric is actually on the surface of the yarn, when denim is washed in a cellulose enzyme bath the indigo dye is removed along with the fibre.

These enzymes actually eat away dyed cellulose fibre, from the surface thus create a stone washed look.

BRIEF INTRODUCTION TO ENZYME AND ENZYMATIC REACTION

* Enzymes are found in plant, animals and micro-organism, where they play an important role in the function of cells

* Enzymes are proteins which catalyze specific chemical reactions and are known as bio-catalysts

* Enzymes enable higher reaction rates with lower energy consumption in comparison to other traditional catalysts.

* Enzymes are designed for acting in living cells, hence they can work at atmospheric pressure and in mild conditions of temperature and pH.

ENZYME WASH CYCLE

Loading of denim Garments (addition of Stones is optional)Desizing with- alpha-amylase Enzyme, or- Oxidative desizeRinsingAdjusting pH to 4.5 to 5.0 with- acetic acid, or- buffer system Heating to 50 to 60 CAddition of cellulose enzymeTumbling for 30 to 60 minutesHot rinsing at > 65 CCold washingSofteningDry tumbling

Activity of cellulose enzyme is judged by its ability to degrade the cellulose to glucose.The activity of cellulose enzyme depends on temperature and pH. Optimum activity of acid cellulose enzyme may be achieved at a pH of 4.5 to 5.0 and a temperature of 60 C.Their optimum activity, however, depends on the type of enzyme and the process where it is applied.

ADVANTAGES OF ENZYME WASH

• Ease of handling, storage and disposal makes enzymes a choice catalyst for any processing industry

• Most economical due to more water saving

* Reduction in pollution, waste, quality variation* Enzymes can be recycled unlike pumice stones or acids* Several dozen pounds of pumice stones can be replaced

with a small quantity of enzymes* Reduce labour engagement as there is no need for the

expensive and time consuming tasks of removing stone fragments from the garments once the wash is completed

* Reduce wear and tear of washing machine components and garments

ACID WASH

It is usually done by dry tumbling the denim garments with pumice stones that are pre-soaked in a solution of sodium hypochlorite (5 to 10%); or potassium permanganate (3 to 6%) in order to facilitate localized bleaching that results in a non-uniform sharp blue/white contrast.

After tumbling colour contrast can further be enhanced by way of giving subsequent optical brightening treatment.

Acid wash is also known as snow, marble, fog white, ice and frosted wash.

ACID WASH CYCLE

Loading of garment With pumice tonesDesizing for about 10 to 15 minutesDrying Dry tumbling for 10 to 30 minutesCooling without Addition of waterPer-oxide washOptical BrighteningSoftening Treatment

DENIM BLEACHING

In this technique, decolouration is done by way of adding strong oxidative bleaching agent like sodium hypochlorite or potassium permanganate during washing.Washing maybe done with or without stones

* Extent of decolouration of denim depends upon strength of bleaches, liquor quantity and treatment time

* Proper after wash or anti-chloring (incase of sodium hypochlorite bleaching agent) of bleached denim to minimize subsequent yellowing and tendering of denim

Wash Cycle of Denim

Loading of Garment with or Without stones DesizingRinsingBleaching for 15 to 30MinutesRinsing with Cold waterOptical brighteningSoftening TreatmentWashed denim

SOME UNCOMMON DENIMS

BUBBLE GUM DENIM

General name for Lycra containing denim that has between 35 to 50% stretch

COLOURED DENIMJeans used to be blue and nothing else. But, now-a-days, denim fabric is available in different colours also. This fabric is woven with dyed yarn either wrap or weft. Coloured denim can also be obtained by piece dyeing process.

CRUSHED DENIMTextured effect achieved through a special fabric construction coupled with wet processing. Fabric is woven with an over twist weft yarn. On washing the yarn shrinks, acquiring a goffre look. The effect can also be improved by bleach and stone wash.

DENIM FROM FOX FIBREDenim fabric manufactured by coloured cotton fibre that grows naturally developed and patented by California cotton breeder Sally Fox. Available in ‘Coyote brown’ with red and green shades Grown in Texas, Arozona and California. NITRA, India has also done work on this line.

MARBEL DENIM

It is an another name for acid wash.

Some crushed denims, if strongly bleached, are also called marble.

ECRU DENIM

The denim, which is not having dyed yarn i.e. only grey yarn in warp & weft.

PRINTED DENIM

Denim printed with pattern such as batik or floral pattern often in contrasting colours mainly meant for adolescents.

REVERSE DENIMWhere the face side and reverse side look alike

SHOT GUN DENIMDenims that have been shot with a gun and sometimes washed to the extreme condition resulting in small holes.

THERMO DENIM / DOUBLE DENIMIn which a light weight fabric either plain, fancy or coloured is glued to the denim. After washing the glue comes off and trouser looks like they have been lined.

VINTAGE DENIMA denim treatment that applies heavy stone washing or a cellulose enzyme wash with or without bleach for an old and worn outlook

PETROLEUM WASHDeveloped in 1992 by US brand Williwear. A left hand denim is enzyme washed until it has lost most of the colour. It is then overdyed and put through a silicone wash, which gives it an oily coating and, in turn a super-soft, butter like hand.

PINTO WASH DENIM

This fabric was developed accidentally. In 1969, warehouses of Cone Mills, USA flooded with water due to hurricane.Millions of yards of denim were soaked with water. When the fabric was dried, an uneven dyeing defect developed on the fabric.To cover up huge losses, a merchandiser of Cone Mills came up with an idea. He suggested to run the fabric through a solution to remove the dye, which resulted faded appearance.This new fabric became very popular and called Pinto Wash Denim.

SANDING DENIM

Abrading fabric with sand-paper for peach skin hand

SALT WATER DENIM

Washed with a high sodium content finish for increasing abrasion levels

SNOW WASH

A variation of acid wash that imparts bright white highlights

SUN WASHING

A very light shade can be achieved by bleaching and toning which looks as if the sun faded the fabric

SAND BLASTING

This process refers to a physical process which creates localized abrasion or colour change on the denim similar to the effect seen on well used jeans. In this process the garments are first stone washed to the degree required and than sand blasted in certain areas such as knees and elbows. The common blasting substance used are metal granules. The other method used to get a similar look is by spraying a solution, containing sodium hypochlorite or potassium paramagnet. After spraying the desired areas on the garment they are neutralized, rinsed softened and dried.

SUPER STONE WASHA prolonged stone wash treatment given for more than six hours. Washing is done in drum washer.The chemical agents required for hard wash are soda ash and soap.Steam is required upto 60-80 C minimum for one hour to finish the process.In the second stage acetic acid wash treatment is used, then the garments are neutralized and rinsed

PEACH SKIN EFFECT DENIM

This effect is created by treating the fabric in order to form a fine protruding, hair-like covering resembling the surface of a peach.The effect can be achieved by a careful selection of the fabric and a tightly controlled wash with a combination of neutral cellulose enzyme and stone.This treatment is often carried out on ecru jeans that are to be garment dyed.The extent of the surface effect depends on the fabric used as well as on the cellulose dose and treatment time.If an equally high amount of acid cellulose is used, the surface will turn out very smooth with absolutely no fuzz on the face.

Thank You…