Performance Evaluation of Water Repellent Finishes on Cotton Fabrics by Spray Tester

Submitted by :
Students Name Reg. No.
Md. Emamul Haque Emon T 201713031
GOVT. OF THE PEOPLE’S REPUBLIC OF BANGLADESH
Textile Finishing (Thesis)
2022
Session : 2016 – 2017 (Admission), Level : 4 , Term : 1
Department : Wet Process Engineering.
 REPORT 
Submitted to :
A.S.M Junaid Hasan
Lecturer (Textile)
Bangabandhu Textile Engineering College
Kalihati, Tangail
B. Sc. in Textile Engineering.
Bangabandhu Textile
Engineering College

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Bangabandhu Textile Engineering College (BTEC) | [3 July, 2022]
No. Topics Page no.
1
Performance Evaluation of Water Repellent Finishes on
Cotton Fabrics by spray tester .
2 - 8
Water Repellent Chemicals 3
Spray Test for Water Repellency Analysis 4
Result and Discussion 7
2
Different drying Techniques used in Textile Industry . 9 - 13
Various Drying System 10
Radio frequency dryer (RF Dryer) 11
Infra-red drying system 12
3
Uses of hydro - extractor in knit fabric finishing . 14 - 17
Technical Data 15
Working Principle of Hydro Extractor Machine 16
CONCLUSION 17
4
An overview of calendar machine used in textile finishing . 18 - 22
Parameters involved in calendaring 19
Chasing Calendars, Friction Calendars 20
Construction of the Rolls 21
Table of Contents

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Performance Evaluation of
Water Repellent Finishes On
Cotton Fabrics by Spray tester.
Department of Wet process engineering,
Bangabandhu Textile Engineering college,
Kalihati, Tangail.
Abstract :
In this study, both woven and knit fabrics were taken to evaluate the performance of water repellent
finishes on cotton fabrics properties. Here, 100% cotton fabrics were treated with different types of
fluorocarbon-based water repellent chemicals at different formulations. The levels of water repellency
of the fabrics were measured in accordance with AATCC 127 hydrostatic head test method and with
ISO 4920:2012 spray rating test method. To assess the performance of water repellent finishes on fabric
properties, GSM, bursting strength, tensile strength, abrasion resistance, air permeability, color fastness
to wash, water, perspiration and rubbing fastness with ISO method were done. The results showed that
the water repellent finish type, concentration and curing temperature were very important parameters to
obtain water repellent fabrics with desirable properties.
Keyword : Water repellency, Water repellent finish, Knit fabric, Woven fabric, Fluorocarbons.
Introduction :
Tendency of any material to resist wetting is called its water repellency. Water repellency of a fabric
depends on several factors including nature of the fibers, yarn structure, fabric porosity, finish applied
and water impact force. In this test water is sprayed on the stretched fabric sample from 150 ±2 mm
height under controlled conditions. A wetted pattern is produced whose size is dependent on the water
repellency of the specimen. The wetted sample is compared by the standard spray ratings to evaluate
the water repellency of it. The merit of a fabric intended for rainwear, wagon covers or tents is judged,
amongst other properties, by its ability to keep water out; conversely, when intended for hose pipes or
canvas buckets, to keep water in. In another direction, some fabrics must exhibit the ability to absorb
water rapidly, toweling being an obvious example. So, there is a relation between water and textile
materials which is very necessary for their end use.
Cotton is a versatile fiber with outstanding quality regards comfort ability. Water repellency is one of
the most common functional properties that is needed for protective clothing without affecting the
comfort ability. Water repellency is defined as the ability of a textile material to resist wetting. The
tendency of a water droplet to spread out over the fabric surface mainly depends on the contact angle of
the water droplet and the fabric surface. Water repellent textiles have many uses including industrial,
consumer and apparel purpose. This repellency can be achieved by implementing a thin surface layer of
water repellent chemicals on textile fibers. Water repellency can be done by the modification of surface
energy of textiles with minimal effects on other functional properties like strength, flexibility,
breathability, softness etc. Polymeric coating on cotton fabric must secure good homogeneity with
preferred properties without deteriorating fabric’s comfort ability like handle, breathability etc. When a

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water repellent chemical is applied on cotton fiber, a monomer that was present in water repellent
chemical with the help of initiator mixture are absorbed onto the fibers and made the fabric water
repellent by formation of the polymeric chains and graft bonds inside the textile structure. Furthermore,
textile materials with modified surface can be obtained even by using low add-on of the monomer by
the interpenetration of components and homogenous distribution of that monomers into the fiber.
There has been a market increase in the commercial use of fluorochemicals in recent years, particularly
to impart water repellency to cotton. It has been reported that various types of fluorochemicals that are
used for textile finishing, mainly used to impart water repellency along with oil repellency.
Water Repellent Chemicals
Three water repellent chemicals were used in this experiment. First water repellent chemical is
fluorocarbon (FC), second is C6 fluorocarbon with dendrimers (FC+D) and third is C6 fluorocarbon
with isocyanate booster (FC+B) and these water repellent chemical’s trade names, types and properties
of all the commercial grades for finishing are listed in Tab. 1. and found from respective chemical’s
brochure.
Spray rating test (ISO 4920-2012 (E)
The test method is used to evaluate the water repellency of the fabric. Spray Test one
of the water repellent evaluation methods which measures resistance of fabric to
surface wetting under mild water impact. The fabric surface is visually rated. This
method is widely used because of it is considered as a quick, easy, inexpensive
screening test. Spray rating tests were done by Spray Tester at National Research
centre NRC, Egypt.
Water Repellent Evaluation Test
Each sample were tested in the standard atmosphere, 25±2°C temperature and 65% RH after
conditioning 24 hrs.
There are three types of water repellent evaluation tests were used.
1) Absorbency test
2) Drop test (it checks the contact angle)

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3) Spray rating test (AATCC 22-2001 test method is used to evaluate the water repellency of
the fabric. Spray rating tests were done by Spray Rating Tester by James H. Heal & Co. Ltd.
Halifax, England).
4) Hydrostatic Head Test (it means water permeability test by which how much the pressure is
required to penetrate the water into the fabric is measured. After water repellent finish, it is
necessary to know how much the pressure increased to force the water through a fabric. It was
done by Shirley hydrostatic head tester, England according to AATCC 127 method.
Spray Test for Water Repellency Analysis
The resistance to surface wetting measurements were made before and after washing using
the Spray Tester M232 (SDL International, Sunnyvale, CA, USA), in accordance with ISO
4920. Figure 2 shows the spray tester used in the resistance to surface wetting tests.
ISO 4920 recommends the use of a five-grade scale of photographic standards for resistance to surface
wetting (1–5); however, during this study, we decided to use the six-grade scale specified in AATCC
TM22, which introduced an additional grade “0”, differentiating between “complete wetting of the
entire specimen face beyond the spray points” and “complete wetting of the entire face of the
specimen”. Table 4 provides verbal descriptions of each degree of the surface wetting resistance scale.

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The tests of water repellency were carried out in three repetitions for each material, assessing the
surface of each specimen on a scale from 0 to 5. Due to great difficulty in assessing the degree of
surface wetting of some specimens, which often did not change significantly after the washing
processes, it was decided to use intermediate grades in
the assessment. Because of the adopted deviation from ISO 4920 standard, the degree of resistance
to surface wetting of the material was determined as the mean value from three measurements, and
it was quoted with an accuracy of 0.1 degree.
2.5. Goniometric Analysis of Surface Properties
The analyses of the surface properties of tested fabrics were carried out by goniometric method, using
a goniometer PGX (Fibro System AB, Stockholm, Sweden). Figure 3 presents the principle of measuring
the contact angle (_) using a goniometer.
Two standard liquids with known surface tensions and different values of dispersive and polar
components were applied (Table 5). A drop of liquid, with a volume of 4 _L, was applied. Five
repetitions for each sample were made. The measurements were carried out at a temperature of 21 _
1 _C, and the relative air humidity was 40 _ 2%.

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Result and Discussion:
Three individual fluorocarbon-based water repellent resins such as fluorocarbon (FC), FC +
dendrimers (FC+D) and FC + booster (FC+B) was chosen in this work and to evaluate the effect
of different concentrations of that resins’ solutions on water repellency, solution’s
concentrations were varied to 10 g/L, 30 g/L and 50 g/L and were applied on plain weave woven
and single jersey (S/J) knit dyed fabrics. Meanwhile, the effects of different curing temperatures
were also determined on water repellency by varying curing temperatures (140°C, 160°C and
180°C). The durability of all the fluorocarbon finished cotton fabrics (woven and knit) were
investigated after repeated laundering in terms of water repellency.

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Conclusion:
The information acquired in this study showed that the water repellent types and their
concentration ranges have a great influence on the woven cotton fabric repellence. The
highest water repellence values were obtained when fluorocarbon-based repellent was
used. Increasing the repellent concentration made the fabrics more water resistant
regardless of repellent type. Cotton fabric treated with finishing A showed higher
Flexural Rigidity than fabric treated with Finishing B, and Ring-spun fabrics showed
more stiffness than Compact-spun fabrics. Environmentally friendly fluorocarbon-free
water repellent chemicals could be a good alternative to fluorocarbon-based water-
repellent chemicals.
Acknowledgements:
I would also like to express my deep gratitude to MICRO FIBRE for providing us the lab
facilities, essentially used during the work. I would also like to thank Essential Clothing Ltd for
providing me knit fabrics. Again, special gratitude also goes to the Wet Processing Lab & the
TTQC Lab of Bangabandhu Textile Engineering college (BTEC).
References:
[ 1] HAL Id: hal-03141218 https://hal.archives-ouvertes.fr/hal-03141218
Submitted on 15 Feb 2021.
[2] Quality and Quantity Assessment of the Water Repellent Properties of Functional
Clothing Materials after Washing. Materials 2022, 15, 3825.
https://doi.org/10.3390/ma15113825

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Different Drying Techniques
used in Textile Industry.
Kalihati, Tangail.
Abstract:
Drying of textiles is an impo1tant operation. In case of conventional chemical finishing, the
impregnated materials contain 60-80% of moisture (depending on eh efficiency of padding
mangle) which has to be brought down to 8-10% before curing. Therefore, a combination of
mechanical methods and drying using steam is widely used to bring down the moisture content
of impregnated material to 8-10% level.
Moisture can be removed from impregnated materials to some extent by mechanical method
such as squeezing, centrifugal extraction or vacuum extraction. These mechanical methods
remove only the moisture which is very loosely bound to the textiles material such as that which
is located in the interstices between the yarns comprising the fabric. Water droplets trapped
within the fibers and yarns and water molecules bounded to the fibers by secondary forces such
as hydrogen bonding, are not removable by mechanical means and must be vaporized in order
to remove then during drying process.
Keyword: Textile drying, Moisture content, mechanical method, Water removes.
Introduction:
The textile mill portion of the textile complex includes many chemical wet processes such as
slashing, dyeing, printing, latex bonding, and finishing. In many of these process eses, drying is
required to remove the excess moisture in the porous material s to produce the de sired product.
For example, the typical steps used to produce latex-backed tufted carpet. As there are many
textile products ranging from yarns to carpets which have to be processed, many different drying
processes are used by the textile industry. To complicate things further, various processes are
used for the same product. Typical drying systems used by the textile industry for drying fabrics.
The term drying is commonly used to describe the process of thermally removing the volatile
substances from a product. In textiles, the term is more generally used to mean the dewatering
of a product. Mechanical dewatering is generally much less expensive than thermal drying.
Thus, as much water as possible is usually removed mechanically.
FIELD OF APPLICATION
Drying can be applied to the following textile materials (BAT for the Textiles Industry, July
2003):
➢ loose fibre ➢ hanks ➢ yarn packages ➢ fabric

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Various Drying System
1. Cylinder Drying
2. Hot air drying
a) Float dryer/loop dryer
b) Tensionless dryer/shrink dryer
c) Stenter machine
3. Radio frequency
4. Pressure drying.
5. Infra-red drying system
Cylinder Drying
• Cylinder is also called drum drying or can drying.
• Here evaporation of water is carried out while fabric is passed round the heated
cylinder surface in open width.
• In this stage, a series of hollow cylinders are arranged
- horizontally in two rows or
- Ve1tically in two or more columns.
• Again, for ve1tical cylinder a1rnngement if one pair of cylinder set is placed
vertically, it is called one stage arrangement and that of two pairs is known as
two stage arrangement.
• Generally, 2 sets of rollers with 5 in every set i.e. (5,5) arrangement is very
common.
• Each cylinder is geared to an adjacent one. The cylinders are placed stepwise so
that the fabric in its travel is in contact with maximum of hot surface.
• The cylinders are made up of stainless-steel sheet. The cylinders are hollow and
cure heated by pressurized steam ( 1.09-2.108 kg/m2).
• Surface temperature of cylinder is 102°-11 o0c.

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Hot Air Drying
Many drying machines use hot air to absorb and remove the moisture from the fabric. Drying
by using hot air stream is less efficient in the utilization of heat than drying by hot cylinder
surfaces since a considerable amount of heat is used to raise the temperature of air stream.
Hot air can be generated by-
• Gas burner (mostly used)
• Steam (heat exchanges)
• Thermo fluid oil
• Electricity (expensive and not industry)
Float Dryer/Loop Dryer
The principle involves in passing the hot air over a wet cloth for faster drying.
Figure – Float dryer
Radio frequency dryer (RF Dryer)
Most dielectric drying in textiles is done with radio-frequency energy. Radio frequency is the
portion of electromagnetic spectrum between about 1-100MHz. The fact that, this range is used
for radio communication accounts for the name radio frequency energy. A radio frequency
drying oven uses high voltage and an oscillating electrical field.
"The beating effect" of dielectric energy occurs through the rapid oscillation of molecular
dipoles within and electrically non-conducting (dielectric) material caused by the application of
an alternating of high frequency voltage.
The material to be dried is exposed to the field as below-
Figure – RF dryer

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The polarity of the electrode charges at a rate equal to the frequency of the RF energy. Polar
molecules, such as water, attempt to line up their poles with the electrical field. The oscillating
polarity causes rapid movement of the water molecules. The friction between molecules caused
by this motion generates heat in the material which causes water to vaporize. RF energy heats
deep within the material and greatly accelerates drying of bulky materials which dry slowly in
convection drying system (e.g. hot air, cylinder drying)
Infra-red drying system:
Invisible IR radiation from electromagnetic wave radiation can be used for drying. In terms of
drying technology, the most significant spectral range is 700-3000 run in which pa1ticles are
displaced more rapid by, (random vibrations) thus wanning the product.
Infrared radiant dryers may be either gas-fired or electric.
Gas fired infra-red dryers use burning gas to heat ceramic emitters which impinge the energy on
the materials passing banks of eh ceramic emitters. Electric infra-red dryers use lamps as the
infra-red some. When a body is heated beyond a ce1tain temperature, its color becomes first pee
red and lights up as it is heated on. The emitted radiation cannot be perceived by the human eye,
yet it exists; it is the infra-red.
Pre dryers in continuous dyeing and finishing processes use infra-red energy because the drying
is uniform and migration of chemicals is minimized. Infra-red drying during application of
coating is also very common.
Figure - Infra-red drying

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Pressure drying
Except RF dryer, this is the only m/c for yam dyeing. The maximum capacity of this type of
dryer is 400 kg. Here compressed air is circulated like dye liquor and extracts water. Thus,
d1ying occurs.
CONCLUSION
As there are many textile products that are to be processed, many different drying systems are
used by the textile industry. To complicate things further, various processes are used for the
same product. Typical drying systems used by the textile industry for drying fabrics and tufted
carpets are briefly discussed in this chapter. No attempt is made to give full design details. Also,
the mechanical, electrical, or control aspects of these dryers are not discussed. The reader can
refer to other chapters of this handbook for more details and additional references.
REFERENCES
1. ML Joseph. Introductory Textile Science, 3rd ed. New York: Holt, Rinehart, and Winston,
1986, p.
2. AS Mujumdar. Handbook of Industrial Drying, 2nd ed, New York: Marcel Dekker, 1995, p.
3. Georgia Institute of Technology. Energy conservation in the Textile Industry: Phase II.
Report No. ORO- 5099-T1. U.S. Department of Energy, 1978, p. 15

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Uses of hydro-extractor in
knit fabric finishing
Kalihati, Tangail.
Abstract:
The hydro extractor is a machine used in the textile processing industry. It is also called a
centrifuge. The hydro extractor is a device that uses centrifugal extraction to remove excess
moisture from the fabric. Through this process, approximately 65% of the water is removed. It
plays an important role after passing through the dyeing section. The hydro extraction method
removes the water dispersed in the fiber through mechanical action (the amount of water varies
with fiber type); this process aims to reduce energy consumption, before the final drying of the
fabric or between various wet treatment stages get on.
Keyword: Hydro extractor, Moisture, Cen centrifugal extraction, energy consumption
Introduction:
The hydro extractor is a machine used in the textile processing industry. It is also called a centrifuge. The
hydro extractor is a device that uses centrifugal extraction to remove excess moisture from the fabric.
Through this process, approximately 65% of the water is removed. It plays an important role after passing
through the dyeing section. The hydro extraction method removes the water dispersed in the fiber through
mechanical action (the amount of water varies with fiber type); this process aims to reduce energy
consumption. Most centrifuges have electric drives for speeds of approx.750–1200 rpm and are generally
provided with automatic control over various ranges. For safety reasons, an interlocking lid is essential on a
centrifuge so that the motor cannot be started until the lid is locked, nor the lid raised until the basket is
stationary again after the machine has been stopped.
When used for dewatering loose stock, the cake of loose fibers is transferred from the dyeing machine to
the centrifuge and hydro-extracted before it is run into the fiber opener as a preliminary stage of drying in
a perforated drum drier. If an immersion centrifuge is used, impregnation of the loose fibers with a spinning
lubricant is also possible. In this case, the material is loaded into the centrifuge, liquor is then pumped in
(until it covers the material), and the goods are finally hydro-extracted. The advantage of such a procedure
lies in the fact that separate treatment of the textile material in an impregnation vat and the reloading of
wet goods into the centrifuge are eliminated. Impregnation of textile material in the impregnation basket of
a centrifuge is generally quicker and more effective for all processes than in a vat. The centrifugal force which
drives the liquor through the goods during centrifuging accelerates penetration. It is possible to carry out
several processes one after the other in an immersion centrifuge. In this case, however, separate drain
channels and liquor tanks must be provided. The basket of an immersion centrifuge has an outer casing
without perforations which surrounds the cylindrical basket of anormal centrifuge (extended conically at the
top). By this means, it is possible to fill it with liquor to the level of the upper rim. Only when the basket is
set in motion does the liquor, which is driven outwards by centrifugal force, rise up the basket casing and
run over the upper rim. Loose fiber material (loose stock) can also be centrifuged continuously. For the

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dewatering of yarn packages, other possible options besides the asymmetrical dewatering of columns of
yarn packages in suitably shaped compartments of the centrifuge include symmetrical dewatering by the
rotation of individual packages or columns of yarn packages which involves less risk of package deformation.
Technical Data:
Working width 1300mm
Machine speed 5~30M/min
Machine for the hydro extractor, softener, air ballooning type of cotton knitted tubular fabrics without
tension, with fabrics entwisting, air balloon, control of the squeezing pressure and control of the final
width of the fabric.
Automatic control of the feeding without tension, no edge mark, final folding without stretching. Versions
with simple or double squeezing and imbuing with softeners.
Functional characteristics:
1) Special design centrifuge for packages is suitable for centrifuging all kinds of yarns with
best result.
2) Perforated indentations are on the inside of the cylindrical basket shell, which correspond in
size to the diameter of the packages. The entire bobbin columns are inserted in the package
carrier.
3) High-quality stainless-steel machine casing is for long service time and pretty outlook
4) Package carrier can be offered to save the working time of loading and unloading yarns for
convenient operation.
5) Advanced inverter control system for timing, automatic braking, and varied revolving speed
as requirement for excellent performance.
6) Pneumatic lid device is for safe operation.
7) Fully controlled by electrical apparatus without machine brakes, thus can reduce
mechanical maintenance greatly.
8) The machine is of super silence and super balance for excellent working environment.

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Working Principle of Hydro Extractor Machine:
When using conventional batch hydroextractor, fiber is unloaded from the dyeing machine into
specially designed fabric bags which allow direct crane loading of the centrifuge. When the
perforated drum is revolved, the water is thrown out because of the centrifugal force. An
extraction cycle of 3–5 min reduces the residual moisture content to approximately 1.0 L/kg dry
fiber (in the case of wool). In case of hanks, they are unloaded directly into the rotating
perforated cage. Hydro extraction reduces the moisture content approximately 0.4 L/kg dry
weight. Hydro extraction is used for drying the washed clothes in domestic washing machines.
Centrifuges with perforated drums or baskets (Ø up to approx. 2000 mm) which oscillate
vertically in ball-and-socket joints suspended on three points are produced in various
designs as pendulating, suspension, cage and vertical centrifuges, also with so called
gliding support bearings as gliding support centrifuges or in horizontal respectively vertical
arrangements as open-width, horizontal and warp-beam centrifuges, etc. Most centrifuges
have electric drives for speeds of approximately 750–1200 rpm and are generally provided
with automatic control over various ranges. For safety reasons, an interlocking lid is
essential on a centrifuge so that the motor cannot be started until the lid is locked, nor the
lid raised until the basket is stationary again after the machine has been stopped.
When used for dewatering loose stock, the cake of loose fibers is transferred from the
dyeing machine to the centrifuge and hydro-extracted before it is run into the fiber opener
as a preliminary stage of drying in a perforated drum drier. If an immersion centrifuge is
used, impregnation of the loose fibers with a spinning lubricant is also possible. In this
case, the material is loaded into the centrifuge, liquor is then pumped in (until it covers the
material), and the goods are finally hydro-extracted.

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The advantage of such a procedure lies in the fact that a separate treatment of the textile
material in an impregnation vat and the reloading of wet goods into the centrifuge are
eliminated. Impregnation of textile material in the impregnation basket of a centrifuge is
generally quicker and more effective for all processes than in a vat. The centrifugal force
which drives the liquor through the goods during centrifuging accelerates penetration. It is
possible to carry out several processes one after the other in an immersion centrifuge. In
this case, however, separate drain channels and liquor tanks must be provided.
The basket of an immersion centrifuge has an outer casing without perforations which
surrounds the cylindrical basket of a normal centrifuge (extended conically at the top). By
this means, it is possible to fill it with liquor to the level of the upper rim. Only when the
basket is set in motion does the liquor, which is driven outwards by centrifugal force, rise
up the basket casing and run over the upper rim. Loose fiber material (loose stock) can also
be centrifuged continuously. For the dewatering of yarn packages, other possible options
besides the asymmetrical dewatering of columns of yarn packages in suitably shaped
compartments of the centrifuge include symmetrical dewatering by the rotation of
individual packages or columns of yarn packages which involves less risk of package
deformation.
CONCLUSION
Hydroextractors are machines which are used in the textile processing industry.
These are mainly centrifuges. The wet material is placed in the extractor, which has a
wall of perforated metal, generally stainless steel. The internal drum rotates at high
speed, thus throwing out the water contained in it. The use of the hydroextractor
significantly reduces the energy required to dry any material. Hydroextractors usually
work on centrifugal force creating a high gravitational force, enhancing water extraction.
Hence the water is separated and the product is obtained in a dry form.
REFERENCES
1. https://textilelearner.net/hydro-extractor-machine-in-textile/
2. https://www.jslaundry.com/Working-principle-of-hydro-extractor-id3227731.html
3. Georgia Institute of Technology. Energy conservation in the Textile Industry: Phase II.
Report No. ORO- 5099-T1. U.S. Department of Energy, 1978, p. 15

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An overview of calendar machine
used in textile finishing
Kalihati, Tangail.
Abstract:
Calendering is a type of mechanical levelling and segmenting process for ‘finishing’ fabrics or
webs to produce a special effect, namely flattening, luster, compacting, glazing, moiré, chreiner,
smoothing, texturing and other embossed patterns by passing in open width between two
adjacent rollers kept under pressure. The passage of material (full-width piece goods) between
two rollers is called nip. The use of calenders to produce flat, compact and polished fabric is
very still popular. From the beginning of fabric manufacturing, it was observed that the
application of pressure by a simple iron or press could alter the properties of fabric. The
alteration in properties depends on the ability of the fabric to be mechanically changed. The use
of calender is an important technique in finishing of cotton, linen rayon and silk materials. On
the other hand, synthetic fibres react to mechanical deformation, but they require the presence
of heat to defeat the physical and thermal memory of the fibres. The object of normal calendering
is to flatten yarns, to close interlacements in fabric and to impart a lustrous, smooth feel to the
fabric.
Keyword: Mechanical finish, Improve Properties of fabric, Technique in finishing.
Introduction:
Calendaring is a process where fabric is compressed by passing it between two or more rolls
under controlled conditions of time, temperature and pressure. A calendar is a machine
consisting of two or more massive rolls which are compressed by means of hydraulic cylinders
applying pressure at the journals. One roll is considered the pattern roll and is responsible for
the finished appearance of the fabric while the other roll is called a bowl and serves as the
pressure back-up for the pattern roll and also serves to transports the fabric through the machine.
There are many types of calendars, each designed to impart specific effects to cloth. The
composition of the rolls, number of passes, temperature controls, moisture control and pressure
can vary to fit the desired effect. For example, the pattern roll can be
engraved and serve to emboss a three-dimensional pattern into the fabric. The engravings can
be shallow or deep depending on the desired effect. The pattern roll can be smooth, made of
steel or nylon to give the fabric a high luster and sheen. The backing bowls can be made from
corn husks, kraft paper, hard or soft rubber and deform to receive the pressure of the pattern roll.
In calendaring, the yarns are flattened and become more oval in shape. This causes them to
spread in two dimensions and closes up the fabric structure, leaving less open spaces between
the yarn crossovers. In the process, the fabric becomes thinner and more lustrous.

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The reason fabrics are calendared is to improve aesthetics. The major fabric changes are: 1.
reduced fabric thickness. 3. increased fabric luster, 3. increased fabric cover, 4. smooth silky
surface feel, 5. reduced air porosity and 6. reduced yarn slippage.
Parameters involved in calendaring:
(1) Fabric structure—a more open structured fabric is affected more easily by calendering.
(2) Nature of the fibre/yarn—a softer fibre or softer spun yarn is affected more easily.
(3) Finish—pretreating the fabric with starch, gums and/or softeners distinctly enhance the
finishing effect.
(4) Moisture content—dry fabric will be less affected than conditioned fabric.
(5) Roller temperature—synthetic fibres react to mechanical deformation in the presence of
heat, and mechanical deformation of natural fibres are also enhanced by heat.
(6) Calender speed—this determines dwell time in nip and consequently the extent of
deformation.
(7) Differential bowl speed—this determines the friction on the fabric’s surface and
consequently the fabric’s lustre.
(8) Nip pressure—high pressure gives a papery finish while reduced pressure results in a soft
and thready appearance of the finished fabric.
(9) Roller composition—the extent of the hardness and its variation on the roller surface
decides the uniformity of a surface finish.
Types of Calendars
The type of calendar used depends on the type of cloth to be run and what the desired effect is
to be. There are embossing calendars, friction calendars, swizzing calendars, chase calendars,
and compaction calendars. The difference between them is the number of rolls and the drive
system.
1. Swizzing Calendars
Swizzing is a British term used to denote that the fabric runs through all of the nips at the same
surface speed as the rolls. Swizzing calendars usually consists of seven to ten bowls and are
run at ambient temperatures. The fabric effect is closed interstices, a smooth appearance and
gloss without the high glaze characteristic of a friction calendar. A schematic of 7 bowl
calendar is shown in figure.
Figure - Swizzing Calendar

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2. Chasing Calendars
Chasing calendars are similar to swizzing calendars. The major difference is that the thread-up
is such that the cloth makes several passes through the nips before it exits to a take-up roll. This
is done by having cloth pass over chasing rolls which feed it back through the nips. The cloth is
compressed against itself with as many as 5 to 6 layers being in a nip. This gives the cloth a
thready-linen appearance and a soft special feel.
Figure - Chase Calendar
3. Friction Calendars
As the name implies, friction calendars (see figure) apply a friction force to the face of the fabric.
This is done by driving the pattern roll faster than the support bowl. Friction is created by speed
differentials ranging from 5% to 100% so it is necessary to have a strong fabric to withstand the
strains. Frictioning produces a high degree of luster on one side and the final effect is similar to
ironing with a hot iron.
Figure 76. Friction Calendar
4. Compaction Calendar
A compaction calendar has an adjustable gap between the pattern roll and bowl. This type of
calendar is used to make filter media of certain thickness.
5. Embossing Calendar
Embossing calendars are normally two or three roll calendars with one engraved roll and one or
two bowls. The patterns range from polished rolls or cire' to very deep floral patterns. Moire is
a watered appearance which resembles paper after it has been wet with water. The moire effect
can be obtained by using a moire pattern embossing roll. Thermoplastic fabrics can be
permanently embossed with

P a g e | 21
heated rolls and the effect can withstand repeated laundering. Natural fibers are more difficult
to emboss and usually starch is needed for the embossing to take; however, this effect is not
durable to laundering. Certain melamine resins can be added prior to embossing and when
properly cured; the embossing effect is more durable.
6. Schreiner Calendar
Often it is desirable to increase fabric luster without overly thinning the cloth. Schreinering is a
method of doing this. Schreinering is actually embossing by the use of a very special pattern.
The pattern roll has anywhere from 250 to 350 lines per inch, etched at 26 degrees from the
vertical. These lines are lightly embossed into the fabric and being regular, reflect light so as to
give the surface a high luster. This operation gives a silk-like brilliance to cotton fabrics.
Schreinering mercerized cotton fabrics gives the nearest resemblance to silk.
Figure - Schreiner Calendar
Construction of the Rolls
1. Pattern Rolls
Pattern rolls are turned from sold steel billets. The pattern is engraved onto the roll surface and
the roll is heat treated to harden it and make the pattern more durable. The rolls are chromed
which also increase wear resistance and protects them from rusting on storage. The center of
these rolls is bored out to accommodate various heating systems. Steam, electrical heaters,
natural gas and recirculating hot oil systems have been used to heat these rolls.
2. Bowls
Bowls are filled with cotton, combination of wool and cotton and/or corn husks. Cotton is used
to produce very hard, dense surfaces. These are not very resilient and are susceptible to being
marked or scarred should hard objects inadvertently pass through with the cloth. Wool or
wool/cotton is used because the surface will be more resilient and less likely to be damaged if a
seam passes through. A disadvantage of wool is that the scales on the fiber tends to pick certain
fabrics and create surface defects. Corn husk is a very pure form of cellulose and makes bowls
that are cheaper and more resilient than cotton, however they are weaker than cotton filled
bowls. Paper is also used to fill bowls. The latest in bowl design is nylon bowls - a one-inch-
thick nylon shell fitted over a roll. The advantage of nylon is it resiliency; it is more resistant to
being marked than are the other surfaces. Seams and wrinkles can run through without having
to refurbish them all the time. Cloth having selvages thicker than the body of the fabric can be
run through without problems. One disadvantage, however, is that temperatures are limited to
less than 3750 F, otherwise the nylon will melt.

P a g e | 22
3. Crowning
When pressure is applied to the journals of both the pattern roll and the bowl, the rolls tend to
deflect. The wider the calendar the greater will be the deflection. To take care of the deflection,
all bowls are crowned, i.e. the diameter of the middle is greater than the diameter at the edges.
The amount of deflection and therefore the amount of crown depends on the pressure per lineal
inch. Therefore it is necessary to change the crown on the bowl to accommodate different
pressures otherwise the calendaring effect will not be uniform across the width of the fabric.
Too little crown will cause weak calendaring of the center as compared to the edges while too
much crown over-calendars the center and under-calendars the edges. Older calendars require
changing of the bowls when different pressure require a different crown profile. Also when the
bowl surface is severely damaged, it must be removed and reground to true it up. Modern
calendars with nylon shells are designed to alleviate these problems. There are two systems
designed to overcome the need to change bowls for different crown profiles. One system uses a
hydraulic reservoir under the nylon shell to change the profile. Chambers across the width of
the bowl can be individually pressurized to accommodate whatever profile is desired. The
second system differs from the above in that the actual calendaring pressure is applied from
within the bowl and not from the pressure applied at the journals.
CONCLUSION
Exactly calendaring is used for woven fabric. Calendering is a thermo-mechanical technique
that involves the use of heat and mechanical pressure, but not chemicals. Textile materials are
taken through the method of calendering to enhance their aesthetic look and handle. Calendering
is a kind of mechanical smoothing and segmenting procedure for ‘finishing’ fabrics or webs to
create a special effect, namely flattening, luster, glazing, compacting, moiré, Schreiner,
texturing, smoothing, and other embossed designs by passing in open width between two inline
rollers kept under pressure.
REFERENCES
1. Chemistry and Technology of Fabric Preparation and Finishing by Dr. Charles Tomasino ;
Page no 226
2. https://textilestudycenter.com/colio/chemistry-and-technology-of-fabric-preparation-and-
finishing/
3. https://www.sciencedirect.com/topics/engineering/calenders

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