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Sizing is the process of applying protective adhesive coating on the yarn surface. This is the most important segment of weaving preparatory process. Because sizing has direct influence on the weaving efficiency. Better the quality of sizing higher the weaving efficiency & vice versa. In fact without sizing, in most of the cases it is almost impossible to run the weaving process. Moreover in case of towel manufacturing rotor (open end) & low twisted yarns are mostly used. There fore sizing should be done very precisely for towel manufacturing.

Flow Chart For Sizing:

 Size Cooking
↓
Creeling
↓
Yarn Feeding
↓
Sizing (in show box)
↓
Drying
↓
Leasing
↓
Denting
↓
Empty Beam Feeding & M/C Running
↓
Ends Cutting
↓
Doffing

Underslashed Warps:
Causes:

• Due to insufficient size concentration
• Improper size feed to the size box
• Variable size level
• Dilution of size
• Strong squeezing of warp

Overslashed Warps:
Causes:

• Due to insufficient splitting of starch at size preparation
• Weak squeezing
• Too deep immersion of the warp into the size box

Sticky Warps:
Causes:

• High sizing speed
• Low drying temperature

Over Dried Warps:
Causes:

• Low sizing speed
• Long stoppage of machine during sizing
• Very high temperature in the drying section

Gum Spots and Smears:
Causes:

• Splashes of size get on the squeezed warp
• Bad stirring of starch at preparation
• Improper coating of felts on the squeezing rollers

Non Uniform Size Regains:
Causes:

• Irregular heating of the size in the box
• Dilution of the size with live steam
• Non uniform pressure of squeezing rollers

Crossed and Lost Ends:
Causes:

• Lease rods are set too far apart
• Broken ends are improperly pieced up
• Bad warping

Improper Build of Beam:
Causes:

• Incorrect spreading of yarn ends in the reed dents

Incorrect Warp Length:
Causes:

• Disarrangement of the measuring and marking mechanism
• Improper adjustment of measuring and marking mechanism

Dirt Stains in Warp:
Causes:

• The size boxes and machine metal parts are dirty
• The size is cooked in non-galvanized iron kettles.

Shinnery:
Causes:

• Due to the friction between the yarn and drying cylinder

Sandy Warp:
Causes:

• Due to not crushed or grind the size material

Hard Sizing:
Causes:

• Excessive application of size material

Size Dropping:
Causes:

• Due to not optimum viscosity of the size solution

Uneven Sizing:
Causes:

• Due to over and under sizing 

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Requirements of Sizing
In order to ensure good technological properties of sized warps, the following requirements should be met in size:
1. Sized warp must be sufficiently strong, smooth & elastic.
2. The sizing process must ensure the application of the required amount of size on the yarn or the required size regain.
3. The tension of the warp yarns at sizing must be regular & constant during all the time of warp unwinding from the warping beams.
4. Yarn stretch & loss in elongation should be within admitted limits.
5. The package, i.e the weavers beam produced must have a cylindrical shape, the necessary winding density & the yarn length.
6. The sizing process must be efficient, economical & must ensure the production of high quality sized warp.

Factors Considered Before the Selection of Size Ingredients
Before selecting the size ingredients the following factors must be considered:
1. It must be Non-degrading to the yarn.
2. It must be compatibility with equipment.
3. It must be easily removal, if necessary.
4. Provides good fabric characteristics if not removed.
5. Least amount of dusting-off during weaving.
6. Cost of the size ingredients must be less.
7. It should not modify the tone of colored warps.
8. No skimming tendency.
9. Easily prepared.
10.Lack of odor.
11.No beam blocking.
12.Compatible with other ingredients.
13.Neutral pH.
14.Insensitive to high heat.
15.Rapid drying.

Name of Some Natural & Synthetic Sizing Agents 

Natural sizing agents:

Synthetic sizing agents:

Drying is a mass transfer process consisting of the removal of water or another solvent by evaporation from a solid, semi-solid or liquid. This process is often used as a final production step before selling or packaging products. In sizing, drying is necessary to bring the sized material hard.

a) Two Cylinder Drying:

1. In this drying process, two copper cylinder are used in which one cylinder is large diameter & other is small comparatively.  
2. Firstly warp sheet is passed below the small cylinder & then over the bigger one.  
3. The yarn is dried while traveling through the circumstances of the cylinder.

Two Cylinder Drying

Advantages:
1. Simple process & cheap.
2. Less risky.
3. Temp. uniform.
4. Almost uniform drying.

Disadvantages:
1. Slow process.
2. Drying efficiency is low.
3. Irregular drying.
4. Due to sticky property of cylinder uneven drying.

(b) Multi Cylinder Drying:

1. In this type of m/c, the drying unit consists of 5 to 7 or 11 cylinders having same diameter are used.
2. All cylinders may be steel cylinders or first two cylinders are teflon coated & rest of aresteel cylinder.
3. The cylinders are heated by passing steam.
4. Heat in initial cylinder is low & gradually increases when moved towards finalcylinder.
5. If large amount of heat is given to the initial, the sized may be backed.
6. If finer yarn is used, then no need to use excess cylinder.

Multi Cylinder Drying

Advantages:
1. High speed process.
2. Uniform drying.
3. Non- sticky so smooth drying.
4. Drying efficiency high.
5. Less time required.

Disadvantages:
1. For high viscosity, stick properly may observed.
2. For friction, yarn hairiness.
3. Shinning effect.
4. Yarn shape may hamper.
5. Possibility of yarn flaten.

2. Hot Air Drying:

• In this m/c, the drying unit is a closed chamber containing a number of guide rollersthrough warp yarn.
• Hot air blown into the chamber causing the moisture in the yarn toevaporate.
• Exhaustion should be used to throw away the moisture.
• If moisture remains inside the chamber it may condense & again fallon the yarn.
• Hot air should be continuously passed through the chamber, so theprocess becomes somewhat costly.

Hot Air Drying

Advantages:
1. Regular drying.
2. Not shinning effect.
3. Non-sticky property.
4. High speed drying.

Disadvantages:
1. Costly process.
2. For closed chamber, reqd more time.
3. Less suitable for fine yarn.
4. Difficult to maintain temperature.

3. Infrared Drying:

• In this machine, the heating chamber consists of a plate which is constantly heated by gas flame.
• The warp sheet is passed over the plate & dried in the process.
• When gas flames are not used, then electronic plate may be used.
• Arrangement should be made to through out the moisture removed from the yarn. This m/c is not used signally.

Advantages:
1. No shining effect.
2. Drying efficiency high.

Disadvantages:
1. Yarn may burn.
2. Higher cost.
3. Difficult to maintain uniform heating.
4. Risk of accident.

• In this type of m/c, preheating is done as cylinder drying method.
• And final drying is done by hot air drying method or infrared drying method.

Infrared Drying

Advantages:
1. Regular drying.
2. Drying efficiency high.
3. Speedy process.

Disadvantages:
1. Shinning effect.
2. High cost. 

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Sizing is a complementary operation which is carried out on warps formed by spun yarns with insufficient tenacity or by continuous filament yarns with zero twist. In general, when sizing is necessary, the yarn is beam warped, therefore all beams corresponding to the beams are fed, as soon as warping is completed, to the sizing machine where they are assembled. Sizing consists of impregnating the yarn with particular substances which form on the yarn surface a film with the aim of improving yarn smoothness and tenacity during the subsequent weaving stage. Thanks to its improved tenacity and elasticity, the yarn can stand without problems the tensions and the rubbing caused by weaving.

In addition to a film former polymer various additives are added to a size mix. Additives may be included in the size mix depending on the particular weaving machine requirements or if a particular type finishing is required after the fabric is woven. A huge variety of additives are used. Most common of them are as follows:

Binders:  

There are a number of polymeric materials that can be used in sizing as binder materials. Binders are true film formers but are generally not used alone for sizing; some sizes are useful as both a primary size and as a binder. Binders are typically used to increase weave ability by promoting the adhesion of the primary film forming size to a specific fiber substrate while reducing the cohesion between sized yarns. By judicious selection of a binder, additional sizing advantages can be realized.Most commonly there are three types of binders used;

1. Acrylics:
2. Pearl corn starch
3. Modified starch
4. Starch derivatives.
5. Polyvinyl alcohol.
6. CMC.
7. Polyester resin binders.
8. Vinyl acetate resins.

Lubricants: 

Lubricant is almost always added to increase abrasion resistance of the yarn which is especially useful for rapiers and projectile machines. Lubricants with anti-sticking agents (lecithin) also prevent sticking of PVA to dry cans. Emulsifiers are added to the wax to improve desizablity. Paraffin or marine glycerides are added to harden the wax and better lubricate the yarns; however, if not removed properly during desizing some lubricants can cause problems in later operations.

Various other additives include humectants, anti-static and anti-foam agents, removable tints (for warp or style identification), preservatives (if the warp or the fabric is to be stored for long periods of time), penetrating agents (to allow the size to penetrate into tightly constructed styles), weighting agents (to make cloth heavier), anti-mildew.

Softeners such as lubricants, soaps and waxes are used to make the yarn sufficiently extensible, they also prevent cracking of size during weaving.

Humectants, such as urea, sugar and glycerin are used to retain moisture in the size product. Moisture makes the size film more flexible and less brittle.

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This is the most used sizing process. About all types of yarns can be sized by slazer sizing process. In this process the warp is passed through a size liquor bath then through a separating unit and cooling unit.

The Slasher Sizing Machine consists of the following seven units:

1. Back beam unit
2. Sizing unit
3. Drying unit
4. Cooling unit
5. Dividing unit/Separating unit
6. Measuring and marking unit 
7. Beaming unit 

Main Parts of Slasher Sizing Machine: 

B = guide bar
C = Tension roller
E = Emersion roller
F = sizing roller
G = squeeze roller
H = Drying cylinder
I = cooling fan
J = guide bar
K, L = lease rods
M = coloring bowl
N = wraith
O = measuring roller
P = tension roller
Q = Nipper roller
R = warp beam
S = Pressure roller
U = reserve box
V = marking roller

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• Coat the warp yarn with a film.
• Impart smoothness.
• Blind the protruding fibres to the yarn surface. 
• Increase elasticity.

• To give a softer feel to the sized yarn.
• To reduce stickiness of yarn.
• To smoothen the yarn.

• To prevent the growth of mildew.
• To prevent spoiling of the size mix during storing it for long time. 
• To help to store the sized yarn.

• To improve the size wet ability.
• Improve the penetration of the size between the fibres.
• Uniform distribution of the sizing solution on the yarn surface is obtained.

• To increase the brightness & remove yellowish color of yarn.
• To prevent dusting off.
• To form a particular shade.

• To give additional weights to the goods.
• To prevent opening of cloth.

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Sizing is a complementary operation which is carried out on warps formed by spun yarns with insufficient tenacity or by continuous filament yarns with zero twist. In general, when sizing is necessary, the yarn is beam warped, therefore all beams corresponding to the beams are fed, as soon as warping is completed, to the sizing machine where they are assembled. Sizing consists of impregnating the yarn with particular substances which form on the yarn surface a film with the aim of improving yarn smoothness and tenacity during the subsequent weaving stage

Thanks to its improved tenacity and elasticity, the yarn can stand without problems the tensions and the rubbing caused by weaving.

The functions of the sizing operation are:-
1. To lay in the protruding fibers in the body of the yarn and to cover weak places by encapsulating the yarn by a protective coating of the size film. The thickness of the size film coating should be optimized. Too thick a coating will be susceptible to easy size shed-off on the loom.

2. To increase the strength of the spun warp yarn without affecting its extensibility. This is achieved by allowing the penetration of the size into the yarn. The size in the yarn matrix will tend to bind all the fibers together. The increase in strength due to sizing is normally expected to be about 10 to 15% with respect to the strength of the unsized yarn. Excessive penetration of the size liquid into the core of the yarn is not desirable because it affects the flexibility of the yarn.

3. To make a weaver’s beam with the exact number of warp threads ready for weaving.

Sizing variables:
A good sizing depends on various factors. During sizing the following variables should be checked and controlled where necessary:

1. Viscosity of the size solution.·
2. Sizing machine speed.·
3. Size add-on levels.·
4. Concentration of the size mixture.
5. Volume of the size box.·
6. Threading arrangements.·
7. Condition of squeeze rolls.
8. Squeezing pressure.·
9. Hardness of squeeze rolls.
10. Diameter of squeeze rolls.
11. Number of size boxes.·
12. Yarn count and size box warp density per unit space.

Why Sizing is Called the Heart of Weaving?
When the yarns are placed in loom machine then it comes to contact with the machine that causes friction. For this reason yarn breakage & yarn rupture may be occurred. As a result, the fabric quality becomes lower so the production also becomes lower. To prevent this problem sizing is done. Sizing gives a protective coating on yarn surface to tolerate the friction on loom machine. The size yarn may reduce the yarn breakage & yarn rupture during weaving process. As a result, fabric quality becomes better & production becomes higher.

Technological Changes Due to Sizing 

Effects of Sizing on Yarn Properties
The following properties of yarn are affected by sizing:

Size is a gelatinous film forming substance in solution or dispersion form, applied normally to warp yarns. It can sometimes be applied to weft yarns.Sizing is the process of applying the size material on yarn.A generic term for compounds that are applied to warp yarn to bind the fiber together and stiffen the yarn to provide abrasion resistance during weaving. Starch, gelatin, oil, wax, and manufactured polymers such as polyvinyl alcohol, polystyrene, polyacrylic acid, and polyacetates are employed. 2. The process of applying sizing compounds. 3. The process of weighing sample lengths of yarn to determine the count.

Objects of Sizing 

1. To protect the yarn from abrasion 

2. To improve the breaking strength of the yarn

3. to increase smoothness of yarn

4. To increase yarn elasticity

5. To decrease hairiness

6. To decrease the generation of static electricity

Types of sizing 

Pure sizing: when the size pick up % is about 3 – 10 % it is called pure sizing.

Light sizing: when the size pick up % is about 11 -16% it is called light sizing.

Medium sizing: when the size pick up % is about 17 – 40 % it is called medium sizing.

Heavy sizing: when the size pick up % is above 40 % then it is called heavy sizing.

Size ia a coating with a gelatinous or other substance to add strength or stiffness or to reduce absorbency.Sizing is the process of applying the size material on yarn.

Properties of Size Ingredients 

• Ease of preparation 
• Uniform viscosity 
• Absence of prolonged congealing and kenning at application temperature 
• pH control 
• absence of foaming properties 
• absence of prolonged tackiness 
• compatibility with other components of the size 
• stability towards decomposition 
• ease of desizing

Size Ingredients and their functions 

Adhesive: example: maize, wheat, corn, potato, ferina, sago, PVC, PVA, CMC

Function: it increases yarn strength and abrasion resistance

Lubricant: example: mineral oil, linseed oil, tallow, Japan was, cotton oil

Function: increases yarn smoothness and elasticity

Antiseptic agent: example: ZnCl2 , Phenol, carboxylic acid, synthetic acid

Function: it helps to store the yarn without being damaged and it also gives protection from bacteria or fungus.

Deliquescent agent: example: MgCl2, glycerin

Function: it prevents brittleness of size and helps to keep the standard moisture regain by not allowing water to enter or exit the fibre.

Weighting agent: example: china clay, French chalk

Function: it increases the weight of the yarn

Wetting agent: example: MgCl2

Function: helps to wet the yarn instantaneously

Tinting agent: example: Blue

Function: it helps o increase the brightness of yarn

Antifoaming agent: example: Benzene, Pyridine

Function: it prevents the formation of foam

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