Calendering process after Textile wet processing.Calendering is a finishing process used on cloth and fabrics. It involves passing fabric under rollers at high temperatures and pressures to smooth, coat, or thin a material. The process is used on fabrics such as moire to produce its watered effect and also on cambric and some types of sateens. Calendering is also used in the production of paper. The process involves passing a single continuous sheet through a number of pairs of heated rolls. Calendering is also used to compress and smooth materials such as siliconerubber, PVCs, vinyl, and textiles.

1. WPE 311: Wet Processing-II
Lecture -2
Humayra Akhter Himu
Assistant Professor
Dept. of Environmental Science & Engineering
Bangladesh University of Textiles
E-mail: humayra@ese.butex.edu.bd
Cell: 01516106453
Calendering

2. What is Calendering
• Calendering is a thermo-mechanical process, i.e. it
involves use of heat and mechanical pressure.
• It is a temporary finish where the fabric is compressed
by passing it between two or more rollers under
controlled conditions of time, temperature, pressure and
a suitable degree of dampness.
• If we want a smooth, glossy, silky touch and highly
lustrous fabric, it is easy to achieve with calendaring
process.

3. Objectives of Calendering
• To upgrade the fabric handle and to impart a smooth silky touch to the fabric.
• To compress the fabric and reduce its thickness.
• To improve the opacity of the fabric.
• To impart different degree of lustre to the fabric.
• To reduce the yarn slippage.

4. Types of Caledering
1. Swizzing Calender
2. Chasing Calender
3. Friction Calender
4. Schreiner Calender
5. Embossing Calender
6. Moiré Calender

5. 1. Swizzing Calender
• It is a British term which denote that fabric runs through all the nips of 5 or 7
bowls universal calender and then either plaiting or batching.
• It usually consists of 7-10 bowls.
• All bowls rotate at same speed.
• Softening and filling agents can be applied to produce lustre.
• It gives close inter stiches, smooth appearance and gloss without high glaze (which
we get from friction calender)
• Smoothness and lustre are increased with the increase of bowl temperature (150-
180°C).

6. 1. Swizzing Calender (contd..) Roller Specification:
1. (at the bottom) closed grained
iron bowl
2. Compressed cotton bowl
3. Highly polished chilled iron, steam
heated bowl.
4. Compressed cotton bowl
5. Compressed cotton bowl
6. Highly polished chilled iron, steam
heated bowl.
7. Compressed cotton bowl

7. 1. Swizzing Calender (contd..)
Advantage:
• Uniform calendaring is obtained
• Remove wrinkles and creases
• Smooth fabric surface can be obtained
• Very high glossy fabric is achieved
• No risk of displacing of fabric

8. 2. Chasing Calender
• It is similar with swizzing calender.
• 5-7 rolls are needed & all of them rotate at same speed.
• The major difference is that the cloth makes several passage through the nips
before it exits to a take-up roll.
• The cloth is compressed as 5-6 layers being superimposed and entering into the nip
again.
• At this the weft of one layer will lie in between two adjacent wefts of the next layer
and give additional pressure.
• Roller pressure and this additional pressure soften the fabric and gives a linen
appearance (soft feel).

9. 2. Chasing Calender (contd..)

10. 2. Chasing Calender (contd..)
Advantage:
• Gives very smooth linen appearance.
• Produce soft handle.
• More the fabric is passed, more the glazy appearance is achieved.
• Removes wrinkles and crease.

11. 3. Friction Calender
• For producing this effect, the top four bowls of a 7-bowl universal calender are lifted
up, disengaging or disconnecting the contact between the third and the fourth bowls, so
as to use only the two or three bottom bowls.
• When the first two bowls alone are used, the arrangement is a two-bowl friction
calender and if the first three are used it is a three-bowl friction calender. The latter
arrangement is shown in the figure below:

12. 3. Friction Calender (contd..)

13. 3. Friction Calender (contd..)
• In this process, the third (top), polished, chilled iron bowl is heated with steam.
• As a further modification, this bowl is rotated by means of special gear wheels such that
its surface speed is double that of the fabric and those of the lower two bowls.
• As a variation, the top bowl may be run at 1.5 times the speed of the lowest bowl, with
the middle bowl running at an intermediate speed.
• Due to the differential bowl speeds, a frictional effect is exerted on the fabric surface.
• A 3-bowl friction calender is generally run at about 30 m/min. A three-bowl calender,
working without friction is run at around 60 m/min, while a seven–bowl calender is run
around 80 m/min.

14. 4. Schreiner Calender
• Schreiner calender is usually a two bowls calendaring mechanism. The upper bowl is
made up of specially polished steel bowl and the lower bowl is made of compressed
cotton.
• The top metallic bowl is engraved with lots of finer line. Usually 200 lines at an angle
of 20° are engraved in every square inch. For some special cases it may be drawn at
45° angle.
• Top bowl can be heated up to 150°C by gas.
• Generally Umbrella cloth and Aniline Black dyed cloth are finished by this calendar.
• Mercerized fabric when treated in this calendar gives Silk finish.

15. 4. Schreiner Calender (contd..)

16. 5. Embossing Calender
Fig: Embossed Roller/Cylinder

17. 5. Embossing Calender (Contd..)
Fig: Embossing effect

18. 5. Embossing Calender (contd..)
• This calender is generally made of two or three bowls. The top chilled iron roll has a
design engraved on it and is heated.
• In two bowl machine, the heated and engraved metal bowl is used in conjunction with a
paper or cotton bowl which is twice the diameter of metal bowl.
• In case of three bowl machine, the engraved metal bowl is placed between two cotton or
paper bowl whose diameter is about three times that of the metal bowl.
• In general embossing, any design that may be engraved on the surface of metal bowl,
may be transferred on to the fabric as a temporary finish.
• This calender is generally used to produce certain effects on bookcloth, imitation
leather and so forth.

19. 5. Embossing Calender (contd..)
Fig: Two bowl embossing calender Fig: Three bowl embossing calender

20. 6. Moiré Calender
Fig: Moiré effect

21. 6. Moiré Calender (contd..)
• The moiré finish produces a wood-grain design on the face side of the fabric.
• Moiré finish can be temporary, durable or permanent.
• Cotton or rayon moiré finish is temporary without pretreatment with resin.
• Durable moiré finish requires initial resin treatment followed by calendering.
• Moiré finish on thermoplastic fiber fabrics are permanent if a heated roller is
used for calendering.
• Methods of producing moiré
• Using engraved cylinder
• Using smooth calender roller

22. 6. Moiré Calender (contd..)
Using engraved cylinder
• In this case engraved roller is used on the calender roller.
• Calender roller flattens one part of the fabric more than other, causing different light
reflectance.
• The different light reflectance cause moiré effect.
• Definite repeat pattern moiré is produced.
Using smooth calender rollers
• Two fabrics, each face to face, are fed through the calender. Ribbed fabrics are mainly
required for this.
• The high pressure on the calender rolls causes the rib to squeeze into each other in
certain areas.
• Creates light reflectance pattern which produces moiré effect.
• The effect is completely random and has no specific pattern.

23. Effects of Calendering depend on following parameter:
• The moisture content of the fabric.
• The number of bowls used in the calender.
• The composition and arrangement of the bowls.
• Bowls pressure.
• Machine speed.

24. Schematic diagram of a calendering machine (full range)