calendaring

8/2/2019 Calendaring

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Calendaring

Calendaring is a finishing process used on cloth where fabric is folded in half and passed under

rollers at high temperatures and pressures. Calendaring is used on fabrics such as moire to produce

its watered effect and also on cambric and some types of sateens.

In preparation for calendaring, the fabric is folded lengthwise with the front side, or face, inside, and

stitched together along the edges. The fabric can be folded together at full width, however this is not

done as often as it is more diff icult. The fabric is then run through rollers that polish the surface and

make the fabric smoother and more lustrous. High temperatures and pressure are used as

well. Fabrics that go through the calendaring process feel thin, glossy and papery.

The calendaring finish is easily destroyed, and does not last well. Washing in water destroys it, as

does wear with time.

Variations

Several different finishes can be achieved through the calendaring process by varying different parts.The main different types of finishes are beetling, watered, embossingand Scheiner.

Beetled

Beetling is a finish given to cotton and linen cloth, and makes it look like satin. In the beetling process

the fabric goes over wooden rollers and is beaten with wooden hammers.

Watered

The watered finish, also known as moire, is produced by using ribbed rollers. These rollers compress

the cloth and the ribs produce the characteristic watermark effect by moving aside threads as well as

compressing them. This leaves some of the threads round while others get compressed and become

flat.

Embossed

In the embossing process the rollers have engraved patterns on them, and the patterns become

stamped onto the fabric. The end result is a raised pattern. This works best with soft fabrics.

Scheiner

Similar to the watered process, in the Scheiner process the rollers are ribbed; only in the Scheiner

process the ribs are very fine, with as many as six hundred ribs per inch under extremely high

pressure. The threads are pressed flat with little lines in them, which cause the fabric to reflect the

light better than a flat surface would. Cloth finished with the Scheiner method has a very high lustre,

which is made more lasting by heating the rollers.


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DecatisingDecatising ordecatizing, also known as crabbing, blowing, and decating, is the process of making

permanent a textile finish on a cloth, so that it does not shrink during garment making. The word

comes from the French dcatir, which means to remove the cati or finish of the wool. Though used

mainly for wool, the term is also applied to processes performed on fabrics of other fibers, suchas cotton, linen or polyester. Crabbing and blowing are minor variations on the general process for

wool, which is to roll the cloth onto a roller and blow steam through it.

Decatized wool fabric is interleaved with a cotton, polyester/cotton or polyester fabric and rolled up

onto a perforated decatizing drum under controlled tension. The fabric is steamed for up to ten

minutes and then cooled down by drawing ambient air through the fabric roll. The piece is then

reversed and steamed again in order to ensure that an even treatment is achieved.

There are several quite different types of wool decatizing machines including batch decatizing

machines, continuous decatizing machines, wet decatising machines and dry decatizing machines.

DesizingDesizing is the process of removing the size material from the warp yarns in woven fabrics.

Sizing agents

Sizing agents are selected on the basis of type of fabric, environmental friendliness, ease of removal,

cost considerations, effluent treatment, etc.

Natural sizing agents

Natural sizing agents are based on natural substances and their derivatives:

Starch and starch derivatives; native starch, degradation starch and chemically modified

starch products

Cellulosic derivatives; carboxymethylcellulose (CMC), methylcellulose and oxyethylcellulose

Protein-based starches; glue, gelatin, albumen

Synthetic sizing agents

Polyacrylates,

Modified polyesters,

Polyvinyl alcohols (PVA),

Styrene/maleic acid copolymers.


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Desizing processes

Desizing, irrespective of what the desizing agent is, involves impregnation of the fabric with the

desizing agent, allowing the desizing agent to degrade or solubilise the size material, and finally to

wash out the degradation products. The major desizing processes are:

Enzymatic desizing of starches on cotton fabrics

Oxidative desizing

Acid desizing

Removal of water-soluble sizes

Enzymatic desizing

Enzymatic desizing is the classical desizing process of degrading starch size on cotton fabrics using

enzymes. Enzymes are complex organic, soluble bio-catalysts, formed by living organisms, that

catalyze chemical reaction in biological processes. Enzymes are quite specific in their action on a

particular substance. A small quantity of enzyme is able to decompose a large quantity of the

substance it acts upon. Enzymes are usually named by the kind of substance degraded in the

reaction it catalyzes.

Amylases are the enzymes that hydrolyses and reduce the molecular weight

of amylose and amylopectin molecules in starch, rendering it water soluble enough to be washed off

the fabric.

Effective enzymatic desizing require strict control of pH, temperature, water

hardness, electrolyte addition and choice of surfactant.

Oxidative desizing

In oxidative desizing, the risk of damage to the cellulose fiber is very high, and its use for desizing is

increasingly rare. Oxidative desizing uses potassium or sodium persulfate or sodium bromite as

an oxidizing agent.

Acid desizing

Cold solutions of dilute sulphuric or hydrochloric acids are used to hydrolyze the starch, however, this

has the disadvantage of also affecting the cellulose fiber in cotton fabrics.

Removal of water-soluble sizes

Fabrics containing water soluble sizes can be desized by washing using hot water, perhaps

containing wetting agents (surfactants) and a mild alkali. The water replaces the size on the outer

surface of the fiber, and absorbs within the fiber to remove any fabric residue.

SanforizationSanforization is a process of treatment used for cotton fabrics mainly and most textiles made from

natural or chemical fibres, patented by Sanford Lockwood Cluett (18741968) in1930.[1]

It is a method

of stretching, shrinking and fixing the woven cloth in both length and width, before cutting and

producing to reduce the shrinkage which would otherwise occur after washing.


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The cloth is continually fed into the sanforizing machine and therein moistened with either water or

steam. A rotating cylinder presses a rubber band against another heated rotating cylinder, thereby the

rubber band briefly gets compressed and afterwards shrinks to its final size. The cloth to be treated is

transported between rubber band and heated cylinder and is forced to follow this brief expansion and

recontraction and thus gets shrunk.

The bigger the pressure applied to the rubber band the bigger the shrinking afterwards.

The aim of the process is a cloth which does not shrink during clothes production by cutting, sewing

or by wearing and washing the finished clothes.

For technical application cloth may be specified to have a shrink-proof value of under 1%.

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