7/30/2019 32645443 Water in Textile Processing

1/3

The properties of water are of high importance, since almost all the processes are carried out inaqueous solution. Therefore, the quality of water used in textile finishing is of great significance.The quality of water is estimated on the basis of the following characteristics: transparency,colour and hardness. Water hardness is determined by the total content of calcium andmagnesium salts and is expressed in milligram equivalent per litre or parts per million (ppm).Water colour and its hardness have a great influence on the quality of textile material and theconsumption of soap dyes and other reagents. The presence of iron, calcium, magnesium, andmanganese salts in water causes roughening of fibres, unlevel dyeing, promotes stain formationand reduces colour fastness. The presence of iron and manganese salts in water causesformation of brownish stains and may provide local destruction of the fabric. The high sorptioncapacity of fibre towards iron and manganese salts prohibits the presence of these salts in watereven in small amounts.

The technological processes of treatment of fibrous materials require the use of water ofa certain quality. The general requirements are : transparency of water, the presence in it of onlytraces of iron and manganese and a small amount of oxygen. The conventional classification ofwater according to its hardness are :

Very soft 15

Soft 15 30

Medium Hard 30 60

Hard 60 100

Very Hard 100 +

Different operations require water of different degree of hardness, characterized by a lowoxygen content, transparency and pH from 7.0 to 8.5. The content of iron salts should not exceed1 ppm. Solutions of soap, dyes, acids and alkalis are prepared with water of hardness of not over2 4 ppm. It is allowed to use water containing iron in an equivalent upto 15 gpl withoutsoftening. It is desirable to use water with 18 to 35 ml, As an exception water of hardenss of 54may temporarily be used.

Process used and Requirement of Water :

The sequence of textile processing is mentioned below. Along with the process, theamount of water required to process 100 Kg of cotton material is mentioned below table :

Table 1Requirement of Water in Different Operation

A For 100 Kg of Cotton

Water in litre

1 Sizing 700

2 Desizing 1,5003 Kierring 1,100

4 Mercerising 4,500

5 Scouring 3,000

6 Bleaching 1,000

7 Direct 5,000

8 Vat 15,000

9 Reactive 5,000

7/30/2019 32645443 Water in Textile Processing

2/3

10 Naphthol 4,000

B For 100 Kg of Silk

Water in litre

1 Plain Wash 2,000

2 Degumming 2,0003 Hot Wash 1,000

4 Cold Wash 1,000

5 Bleaching 2,000

6 Hot Wash 1,000

7 Cold Wash 1,000

8 Dyeing 2,000

9 Hot Wash 2,000

10 Cold Wash 1,000

11 Finishing 1,000

Water for Boiling

Mostly pure water is converted into steam. The impurities in water causes (1) scaleformation, (2) corrosion and (3) foaming. This means that water meant for steam must be soft andmust not contain too much dissolved material otherwise a deposit of CaCO3 & CaSO4 mainly willbe formed on the wall of the boiler. The formation of hard insulating crust, called boiler scalecauses a much greater consumption of fuel and also a rapid depreciation of the boiler due tooverheating. Under the stress of continued overheating, the boiler may give way and burst due tounequal expansion of the body of the boiler and scale. Further too much of dissolved matter inboiler water causes foaming and frothing. To avoid all these abnormalities, water should besoftened by Bakelite process or by using sodium hexa meta phosphate.

Water for Bleaching, Scouring & Washing

In scouring, bleaching and washing, water is used again and again in each and everyoperation. The water may be hot or cold. Iron, Magnesium & Calcium salts should be removed forscouring and bleaching. Iron will form a dull shade after scouring and after bleaching; a yellowtinge will be obtained. For washing, water should be soft, otherwise much soap will be used forwater and it results in unnecessary wastage of soap. Water containing suspended organic mattershould not be used for scouring and bleaching purpose.

Water for Dyeing

Water is quite important to dye a fibre, yarn or fabric. The dyestuff is transferred to thefibre from the dye bath and it deposited on the fibre surface. Further, the dyestuff is held to thefibre by secondary forces. The dye bath is prepared by means of water, dyestuff and otherchemicals. Iron salts should be removed from water before dyeing, as it would create a dull

shade. In this case, sometimes, dyeing may be uneven. Water should be sufficiently rectifiedbefore dyeing for a better and uniform dyeing.

Water for Printing

Water is used as a solvent and also as medium with gum in printing. The amount of waterused is relatively small than that of dyeing. The dyestuff, if soluble in water will be used bydissolving that in limited water. Insoluble dyestuffs in water are used in pasting. The water shouldbe soft and must not contain any impurities like that of dyeing. After printing, water in form of

7/30/2019 32645443 Water in Textile Processing

3/3

steam is applied on the printed cloth by means of pressure for a better penetration of the dyemolecule in the fabric.

Water for Finishing

Water acts as excellent softening agent for many types of fabrics. Most of the fabrics feelsofter in summer, after holding a larger amount of water than in winter. Water used for finishingshould be soft and should not contain any impurities.