Preamble
This is the ninety-first post in the "Art Resource" series, specifically aimed to construct an appropriate knowledge base in order to develop an artistic voice in ArtCloth.
Other posts in this series are:
Glossary of Cultural and Architectural Terms
Units Used in Dyeing and Printing of Fabrics
Occupational, Health & Safety
A Brief History of Color
The Nature of Color
Psychology of Color
Color Schemes
The Naming of Colors
The Munsell Color Classification System
Methuen Color Index and Classification System
The CIE System
Pantone - A Modern Color Classification System
Optical Properties of Fiber Materials
General Properties of Fiber Polymers and Fibers - Part I
General Properties of Fiber Polymers and Fibers - Part II
General Properties of Fiber Polymers and Fibers - Part III
General Properties of Fiber Polymers and Fibers - Part IV
General Properties of Fiber Polymers and Fibers - Part V
Protein Fibers - Wool
Protein Fibers - Speciality Hair Fibers
Protein Fibers - Silk
Protein Fibers - Wool versus Silk
Timelines of Fabrics, Dyes and Other Stuff
Cellulosic Fibers (Natural) - Cotton
Cellulosic Fibers (Natural) - Linen
Other Natural Cellulosic Fibers
General Overview of Man-Made Fibers
Man-Made Cellulosic Fibers - Viscose
Man-Made Cellulosic Fibers - Esters
Man-Made Synthetic Fibers - Nylon
Man-Made Synthetic Fibers - Polyester
Man-Made Synthetic Fibers - Acrylic and Modacrylic
Man-Made Synthetic Fibers - Olefins
Man-Made Synthetic Fibers - Elastomers
Man-Made Synthetic Fibers - Mineral Fibers
Man Made Fibers - Other Textile Fibers
Fiber Blends
From Fiber to Yarn: Overview - Part I
From Fiber to Yarn: Overview - Part II
Melt-Spun Fibers
Characteristics of Filament Yarn
Yarn Classification
Direct Spun Yarns
Textured Filament Yarns
Fabric Construction - Felt
Fabric Construction - Nonwoven fabrics
A Fashion Data Base
Fabric Construction - Leather
Fabric Construction - Films
Glossary of Colors, Dyes, Inks, Pigments and Resins
Fabric Construction – Foams and Poromeric Material
Knitting
Hosiery
Glossary of Fabrics, Fibers, Finishes, Garments and Yarns
Weaving and the Loom
Similarities and Differences in Woven Fabrics
The Three Basic Weaves - Plain Weave (Part I)
The Three Basic Weaves - Plain Weave (Part II)
The Three Basic Weaves - Twill Weave
The Three Basic Weaves - Satin Weave
Figured Weaves - Leno Weave
Figured Weaves – Piqué Weave
Figured Fabrics
Glossary of Art, Artists, Art Motifs and Art Movements
Crêpe Fabrics
Crêpe Effect Fabrics
Pile Fabrics - General
Woven Pile Fabrics
Chenille Yarn and Tufted Pile Fabrics
Knit-Pile Fabrics
Flocked Pile Fabrics and Other Pile Construction Processes
Glossary of Paper, Photography, Printing, Prints and Publication Terms
Napped Fabrics – Part I
Napped Fabrics – Part II
Double Cloth
Multicomponent Fabrics
Knit-Sew or Stitch Through Fabrics
Finishes - Overview
Finishes - Initial Fabric Cleaning
Mechanical Finishes - Part I
Mechanical Finishes - Part II
Additive Finishes
Chemical Finishes - Bleaching
Glossary of Scientific Terms
Chemical Finishes - Acid Finishes
Finishes: Mercerization
Finishes: Waterproof and Water-Repellent Fabrics
Finishes: Flame-Proofed Fabrics
Finishes to Prevent Attack by Insects and Micro-Organisms
Other Finishes
Shrinkage - Part I
Shrinkage - Part II
Progressive Shrinkage and Methods of Control
Durable Press and Wash-and-Wear Finishes - Part I
Durable Press and Wash-and-Wear Finishes - Part II
Durable Press and Wash-and-Wear Finishes - Part III
Durable Press and Wash-and-Wear Finishes - Part IV
Durable Press and Wash-and-Wear Finishes - Part V
The General Theory of Dyeing – Part I
The General Theory Of Dyeing - Part II
Natural Dyes
Natural Dyes - Indigo
Mordant Dyes
Premetallized Dyes
Azoic Dyes
Basic Dyes
Acid Dyes
Disperse Dyes
Direct Dyes
Reactive Dyes
Sulfur Dyes
Blends – Fibers and Direct Dyeing
The General Theory of Printing
There are currently eight data bases on this blogspot, namely, the Glossary of Cultural and Architectural Terms, Timelines of Fabrics, Dyes and Other Stuff, A Fashion Data Base, the Glossary of Colors, Dyes, Inks, Pigments and Resins, the Glossary of Fabrics, Fibers, Finishes, Garments and Yarns, Glossary of Art, Artists, Art Motifs and Art Movements, Glossary of Paper, Photography, Printing, Prints and Publication Terms and the Glossary of Scientific Terms, which has been updated to Version 3.5. All data bases will be updated from time-to-time in the future.
If you find any post on this blog site useful, you can save it or copy and paste it into your own "Word" document etc. for your future reference. For example, Safari allows you to save a post (e.g. click on "File", click on "Print" and release, click on "PDF" and then click on "Save As" and release - and a PDF should appear where you have stored it). Safari also allows you to mail a post to a friend (click on "File", and then point cursor to "Mail Contents On This Page" and release). Either way, this or other posts on this site may be a useful Art Resource for you.
The Art Resource series will be the first post in each calendar month. Remember - these Art Resource posts span information that will be useful for a home hobbyist to that required by a final year University Fine-Art student and so undoubtedly, some parts of any Art Resource post may appear far too technical for your needs (skip over those mind boggling parts) and in other parts, it may be too simplistic with respect to your level of knowledge (ditto the skip). The trade-off between these two extremes will mean that Art Resource posts will hopefully be useful in parts to most, but unfortunately may not be satisfying to all!
Relaxation Shrinkage and Methods of Control
Knit Fabrics
Knit fabrics shrink because the loops are elongated 10 to 35% lengthwise in knitting and in wet finishing, as shown in the figure below, thus making the fabric longer and narrower than it should be.
Knit Stitches. Left, before orientation. Right, after orientation.
During home laundering the stitches will reorient themselves to their normal shape, and the garment will become shorter and wider. Mechanical methods of shrinkage control for knit fabrics consist of using a spreader to stretch the fabric crosswise to reorient the stitches.
The fabrics are then dried on a special tensionless calendar or they may be tumble dried. Completed garments may also be tumble dried to give them a controlled shrinkage. At the present time, mechanical relaxation shrinkage control treatments are usually done in conjunction with a resin finish.
Woven Fabrics
All woven fabrics shrink when the strains of weaving, warp yarn sizing, and wet finishing are released when the fabric gets wet in laundering. The warp yarns are stitched out straight, while they are on the loom, and the filling is inserted in a straight line. The filling takes on a crimp as it is beaten back into the cloth, but the warp stays straight. When the fabric is thoroughly wet and allowed to relax, the yarns re-adjust themselves and the warp yarns move to a strip position.
Left: position of the fabric on the loom. Right: After the fabric relaxes when it becomes wet.
This crimp shortens the fabric in the warp direction. With the exception of crepe fabric, less change occurs in the filling direction.
Compressive shrinkage processes are used on woven fabrics of cotton, linen and high-wet-modulus rayon. Regular rayons will not hold a compressive shrinkage treatment because of the high swelling and wet elongation of the rayon fibers.
Sanforize and Rigmel are trade names for compressive shrinkage processes used on woven cloth. The principles involved can be demonstrated by placing a rubber band over the cloth. When the fist is opened and the band is released, the cloth will be squeezed or compressed.
Sanforizing Process
The sanforizing is a mechanical finishing process of treating textile fabrics to prevent the normal dimensional alternation of warp and weft. It is also called anti-shrinkage finishing process. It is a process of treatment used for cotton fabrics mainly and also for some other textiles made from natural and synthetic fibres. 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 wash.
Principle
Sanforizing process is based on the principle that when an elastic felt blanket is passed around a metal roller in contact with it, its outer surface is extended and the inner surface contracted. So the process is called controlled compressive shrinkage process. The process of sanforizing includes the stretching and manipulation of the fabric before it is washed.
During the sanforization process, the fabric is fed into a sanforizing machine where it is treated with water or steam to promote shrinkage, then pressed against a heated rubber band to relax and re-contract the fibers.
The amount of potential wash shrinkage must be determined prior to shrinking. A full width sample is wash-tested according to the test method. After the lengthwise and width wise shrinkage has been determined, the compressive shrinkage machine can be adjusted accordingly.
The cloth is continually fed into the sanforizing machine and therein moistened with either water or steam. A rotating cylinder presses a rubber sleeve against another, heated, rotating cylinder. Thereby the sleeve briefly gets compressed and laterally expanded, afterwards relaxing to its normal thickness. The cloth to be treated is transported between the rubber sleeve and heated cylinder and is forced to follow this brief compression and lateral expansion, and relaxation. It thus gets shrunk.
The greater the pressure applied to the rubber sleeve, the bigger the shrinking afterwards. The process may be repeated.
Schematic Process
The process of Sanforizing can be described by the following schematic below:
* Fabric (F) passes through the skyer (S) or other moistening device and is moistened by water and/or steam. This will lubricate the fibers and promote shrink ability within the fabric.
* Fabric is moistened in such a way that every single thread achieves a moisture content of approximately 15%.
* Above step allows compression of the fabric with very little resistance.
* When the fabric passes through the clip expander (C), we obtain the required width. The clip expander also transports the fabric to the most important part of the machine: the rubber belt unit (indicated by arrows in above figure).
* In the close-up of above figure, we see the endless rubber belt (R). By squeezing rubber belt (R) between pressure roll (P) and rubber belt cylinder (RB), we obtain an elastically stretching of the rubber belt surface.
* The more we squeeze the rubber belt, the more the surface is stretched. This point of squeezing is known as the pressure zone, or the nip point.
* Fabric (F) is now fed into the pressure zone.
* When leaving the pressure zone, the rubber belt recovers itself and the surface returns to its original length carrying the fabric with it. The effect of this action is a shorting of the warp yarn which packs the filling yarns closer together. At this actual moment, shrinkage occurs.
* After compaction within the rubber belt unit, the fabric enters the dryer (D). Here the fibers are locked in their shrunken state by removing the moisture from the fabric.
* After the compressive shrinkage process is completed, another sample of the fabric is taken.
* This sample is also wash-tested. The final result of this test must meet the Sanforized Standard, in length and width before it may carry the Sanforized label.
* All Sanforized Licensees are contractually obligated to follow the required test method and meet the standards set forth by The Sanforized Company.
Research has shown that faulty laundering will cause compressively shrunk fabrics to shrink as much as 6%. Tumble drying may also compress yarns beyond their normal shrinkage.
The trade name "Sanforized Plus" may be used on wash-and-wear and durable-press garments that meet specified standards of shrinkage control, wrinkle resistance, smoothness after washing, tensile strength and tear strength.
London shrunk process is a 200-year-old relaxation finish for wool fabrics, which removes strains caused by spinning, weaving and finishing.
At first the wool was laid out in the fields of the city of London and the dew soothed away the stresses and so improved the hand of the fabric. While techniques have been modernised, there is still much hand labour involved. A wet blanket, wool or cotton, is placed on a long platform, a layer of cloth is then spread on it, and alternate layers of blanket and cloth are then built up. Sufficient weight is placed on top to force the moisture from the blankets into the wool. The cloth is left in the pile for about 12 hours. The cloth is then dried in natural room air by hanging it over sticks. When dry, the cloth is subjected to hydraulic pressing by building up layers of cloth and specially made press boards with a preheated metal plate inserted at intervals. A preheated plate is also placed on the top and bottom of the pile. This set-up of cloth, boards, and plates is kept under 3,000 pounds pressure for 10 to 12 hours. London shrinking is done for men's wear fine worsteds - not for woollens or women's wear.
Today the right to use the label "Genuine London Process" is licensed by the Parrott group of companies. Clothworkers of London, Leeds and Huddersfield to garment makers all over the world. A label from a suit is shown below.
The permanent set finish Siroset, which produces washable, wrinkle free wool fabrics, is now applied to some fabrics during the London Shrunk processing.
Skirt produced using the Siroset process.
A similar method for home use is that of rolling wool cloth in a wet sheet, allowing it to stand for six hours, and then placing it flat on a table or floor to dry. If it is straightened while wet, pressing may be unnecessary. This is the best means for straightening wool which has been tendered or debated "off-grain". It should not be used on wool crepe. Fabrics that have a napped surface, such as wool broadcloth or some wool flannels, may be changed in appearance. Wool fabrics should always be tested for shrinkage prior to cutting. A simple method of testing is to draw a right angle on the ironing board, place the warp edge along one side and the filling edge along the other side, and hold a stream iron over the fabric. If either edge draws away from the pencil line, the fabric will shrink during steam pressing and it should be shrunk.
References:
[1] N. Hollen and J. Saddler, Textiles, 3rd Edition, MacMillan Company, London (1968).
[2]https://textileinsight.blogspot.com/2014/09/sanforizing-machine-and-process.html
This is the ninety-first post in the "Art Resource" series, specifically aimed to construct an appropriate knowledge base in order to develop an artistic voice in ArtCloth.
Other posts in this series are:
Glossary of Cultural and Architectural Terms
Units Used in Dyeing and Printing of Fabrics
Occupational, Health & Safety
A Brief History of Color
The Nature of Color
Psychology of Color
Color Schemes
The Naming of Colors
The Munsell Color Classification System
Methuen Color Index and Classification System
The CIE System
Pantone - A Modern Color Classification System
Optical Properties of Fiber Materials
General Properties of Fiber Polymers and Fibers - Part I
General Properties of Fiber Polymers and Fibers - Part II
General Properties of Fiber Polymers and Fibers - Part III
General Properties of Fiber Polymers and Fibers - Part IV
General Properties of Fiber Polymers and Fibers - Part V
Protein Fibers - Wool
Protein Fibers - Speciality Hair Fibers
Protein Fibers - Silk
Protein Fibers - Wool versus Silk
Timelines of Fabrics, Dyes and Other Stuff
Cellulosic Fibers (Natural) - Cotton
Cellulosic Fibers (Natural) - Linen
Other Natural Cellulosic Fibers
General Overview of Man-Made Fibers
Man-Made Cellulosic Fibers - Viscose
Man-Made Cellulosic Fibers - Esters
Man-Made Synthetic Fibers - Nylon
Man-Made Synthetic Fibers - Polyester
Man-Made Synthetic Fibers - Acrylic and Modacrylic
Man-Made Synthetic Fibers - Olefins
Man-Made Synthetic Fibers - Elastomers
Man-Made Synthetic Fibers - Mineral Fibers
Man Made Fibers - Other Textile Fibers
Fiber Blends
From Fiber to Yarn: Overview - Part I
From Fiber to Yarn: Overview - Part II
Melt-Spun Fibers
Characteristics of Filament Yarn
Yarn Classification
Direct Spun Yarns
Textured Filament Yarns
Fabric Construction - Felt
Fabric Construction - Nonwoven fabrics
A Fashion Data Base
Fabric Construction - Leather
Fabric Construction - Films
Glossary of Colors, Dyes, Inks, Pigments and Resins
Fabric Construction – Foams and Poromeric Material
Knitting
Hosiery
Glossary of Fabrics, Fibers, Finishes, Garments and Yarns
Weaving and the Loom
Similarities and Differences in Woven Fabrics
The Three Basic Weaves - Plain Weave (Part I)
The Three Basic Weaves - Plain Weave (Part II)
The Three Basic Weaves - Twill Weave
The Three Basic Weaves - Satin Weave
Figured Weaves - Leno Weave
Figured Weaves – Piqué Weave
Figured Fabrics
Glossary of Art, Artists, Art Motifs and Art Movements
Crêpe Fabrics
Crêpe Effect Fabrics
Pile Fabrics - General
Woven Pile Fabrics
Chenille Yarn and Tufted Pile Fabrics
Knit-Pile Fabrics
Flocked Pile Fabrics and Other Pile Construction Processes
Glossary of Paper, Photography, Printing, Prints and Publication Terms
Napped Fabrics – Part I
Napped Fabrics – Part II
Double Cloth
Multicomponent Fabrics
Knit-Sew or Stitch Through Fabrics
Finishes - Overview
Finishes - Initial Fabric Cleaning
Mechanical Finishes - Part I
Mechanical Finishes - Part II
Additive Finishes
Chemical Finishes - Bleaching
Glossary of Scientific Terms
Chemical Finishes - Acid Finishes
Finishes: Mercerization
Finishes: Waterproof and Water-Repellent Fabrics
Finishes: Flame-Proofed Fabrics
Finishes to Prevent Attack by Insects and Micro-Organisms
Other Finishes
Shrinkage - Part I
Shrinkage - Part II
Progressive Shrinkage and Methods of Control
Durable Press and Wash-and-Wear Finishes - Part I
Durable Press and Wash-and-Wear Finishes - Part II
Durable Press and Wash-and-Wear Finishes - Part III
Durable Press and Wash-and-Wear Finishes - Part IV
Durable Press and Wash-and-Wear Finishes - Part V
The General Theory of Dyeing – Part I
The General Theory Of Dyeing - Part II
Natural Dyes
Natural Dyes - Indigo
Mordant Dyes
Premetallized Dyes
Azoic Dyes
Basic Dyes
Acid Dyes
Disperse Dyes
Direct Dyes
Reactive Dyes
Sulfur Dyes
Blends – Fibers and Direct Dyeing
The General Theory of Printing
There are currently eight data bases on this blogspot, namely, the Glossary of Cultural and Architectural Terms, Timelines of Fabrics, Dyes and Other Stuff, A Fashion Data Base, the Glossary of Colors, Dyes, Inks, Pigments and Resins, the Glossary of Fabrics, Fibers, Finishes, Garments and Yarns, Glossary of Art, Artists, Art Motifs and Art Movements, Glossary of Paper, Photography, Printing, Prints and Publication Terms and the Glossary of Scientific Terms, which has been updated to Version 3.5. All data bases will be updated from time-to-time in the future.
If you find any post on this blog site useful, you can save it or copy and paste it into your own "Word" document etc. for your future reference. For example, Safari allows you to save a post (e.g. click on "File", click on "Print" and release, click on "PDF" and then click on "Save As" and release - and a PDF should appear where you have stored it). Safari also allows you to mail a post to a friend (click on "File", and then point cursor to "Mail Contents On This Page" and release). Either way, this or other posts on this site may be a useful Art Resource for you.
The Art Resource series will be the first post in each calendar month. Remember - these Art Resource posts span information that will be useful for a home hobbyist to that required by a final year University Fine-Art student and so undoubtedly, some parts of any Art Resource post may appear far too technical for your needs (skip over those mind boggling parts) and in other parts, it may be too simplistic with respect to your level of knowledge (ditto the skip). The trade-off between these two extremes will mean that Art Resource posts will hopefully be useful in parts to most, but unfortunately may not be satisfying to all!
Relaxation Shrinkage and Methods of Control
Knit Fabrics
Knit fabrics shrink because the loops are elongated 10 to 35% lengthwise in knitting and in wet finishing, as shown in the figure below, thus making the fabric longer and narrower than it should be.
During home laundering the stitches will reorient themselves to their normal shape, and the garment will become shorter and wider. Mechanical methods of shrinkage control for knit fabrics consist of using a spreader to stretch the fabric crosswise to reorient the stitches.
The fabrics are then dried on a special tensionless calendar or they may be tumble dried. Completed garments may also be tumble dried to give them a controlled shrinkage. At the present time, mechanical relaxation shrinkage control treatments are usually done in conjunction with a resin finish.
Woven Fabrics
All woven fabrics shrink when the strains of weaving, warp yarn sizing, and wet finishing are released when the fabric gets wet in laundering. The warp yarns are stitched out straight, while they are on the loom, and the filling is inserted in a straight line. The filling takes on a crimp as it is beaten back into the cloth, but the warp stays straight. When the fabric is thoroughly wet and allowed to relax, the yarns re-adjust themselves and the warp yarns move to a strip position.
This crimp shortens the fabric in the warp direction. With the exception of crepe fabric, less change occurs in the filling direction.
Compressive shrinkage processes are used on woven fabrics of cotton, linen and high-wet-modulus rayon. Regular rayons will not hold a compressive shrinkage treatment because of the high swelling and wet elongation of the rayon fibers.
Sanforize and Rigmel are trade names for compressive shrinkage processes used on woven cloth. The principles involved can be demonstrated by placing a rubber band over the cloth. When the fist is opened and the band is released, the cloth will be squeezed or compressed.
Sanforizing Process
The sanforizing is a mechanical finishing process of treating textile fabrics to prevent the normal dimensional alternation of warp and weft. It is also called anti-shrinkage finishing process. It is a process of treatment used for cotton fabrics mainly and also for some other textiles made from natural and synthetic fibres. 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 wash.
Principle
Sanforizing process is based on the principle that when an elastic felt blanket is passed around a metal roller in contact with it, its outer surface is extended and the inner surface contracted. So the process is called controlled compressive shrinkage process. The process of sanforizing includes the stretching and manipulation of the fabric before it is washed.
During the sanforization process, the fabric is fed into a sanforizing machine where it is treated with water or steam to promote shrinkage, then pressed against a heated rubber band to relax and re-contract the fibers.
The amount of potential wash shrinkage must be determined prior to shrinking. A full width sample is wash-tested according to the test method. After the lengthwise and width wise shrinkage has been determined, the compressive shrinkage machine can be adjusted accordingly.
The cloth is continually fed into the sanforizing machine and therein moistened with either water or steam. A rotating cylinder presses a rubber sleeve against another, heated, rotating cylinder. Thereby the sleeve briefly gets compressed and laterally expanded, afterwards relaxing to its normal thickness. The cloth to be treated is transported between the rubber sleeve and heated cylinder and is forced to follow this brief compression and lateral expansion, and relaxation. It thus gets shrunk.
The greater the pressure applied to the rubber sleeve, the bigger the shrinking afterwards. The process may be repeated.
Schematic Process
The process of Sanforizing can be described by the following schematic below:
* Fabric (F) passes through the skyer (S) or other moistening device and is moistened by water and/or steam. This will lubricate the fibers and promote shrink ability within the fabric.
* Fabric is moistened in such a way that every single thread achieves a moisture content of approximately 15%.
* Above step allows compression of the fabric with very little resistance.
* When the fabric passes through the clip expander (C), we obtain the required width. The clip expander also transports the fabric to the most important part of the machine: the rubber belt unit (indicated by arrows in above figure).
* In the close-up of above figure, we see the endless rubber belt (R). By squeezing rubber belt (R) between pressure roll (P) and rubber belt cylinder (RB), we obtain an elastically stretching of the rubber belt surface.
* The more we squeeze the rubber belt, the more the surface is stretched. This point of squeezing is known as the pressure zone, or the nip point.
* Fabric (F) is now fed into the pressure zone.
* When leaving the pressure zone, the rubber belt recovers itself and the surface returns to its original length carrying the fabric with it. The effect of this action is a shorting of the warp yarn which packs the filling yarns closer together. At this actual moment, shrinkage occurs.
* After compaction within the rubber belt unit, the fabric enters the dryer (D). Here the fibers are locked in their shrunken state by removing the moisture from the fabric.
* After the compressive shrinkage process is completed, another sample of the fabric is taken.
* This sample is also wash-tested. The final result of this test must meet the Sanforized Standard, in length and width before it may carry the Sanforized label.
* All Sanforized Licensees are contractually obligated to follow the required test method and meet the standards set forth by The Sanforized Company.
Research has shown that faulty laundering will cause compressively shrunk fabrics to shrink as much as 6%. Tumble drying may also compress yarns beyond their normal shrinkage.
The trade name "Sanforized Plus" may be used on wash-and-wear and durable-press garments that meet specified standards of shrinkage control, wrinkle resistance, smoothness after washing, tensile strength and tear strength.
London shrunk process is a 200-year-old relaxation finish for wool fabrics, which removes strains caused by spinning, weaving and finishing.
At first the wool was laid out in the fields of the city of London and the dew soothed away the stresses and so improved the hand of the fabric. While techniques have been modernised, there is still much hand labour involved. A wet blanket, wool or cotton, is placed on a long platform, a layer of cloth is then spread on it, and alternate layers of blanket and cloth are then built up. Sufficient weight is placed on top to force the moisture from the blankets into the wool. The cloth is left in the pile for about 12 hours. The cloth is then dried in natural room air by hanging it over sticks. When dry, the cloth is subjected to hydraulic pressing by building up layers of cloth and specially made press boards with a preheated metal plate inserted at intervals. A preheated plate is also placed on the top and bottom of the pile. This set-up of cloth, boards, and plates is kept under 3,000 pounds pressure for 10 to 12 hours. London shrinking is done for men's wear fine worsteds - not for woollens or women's wear.
Today the right to use the label "Genuine London Process" is licensed by the Parrott group of companies. Clothworkers of London, Leeds and Huddersfield to garment makers all over the world. A label from a suit is shown below.
The permanent set finish Siroset, which produces washable, wrinkle free wool fabrics, is now applied to some fabrics during the London Shrunk processing.
A similar method for home use is that of rolling wool cloth in a wet sheet, allowing it to stand for six hours, and then placing it flat on a table or floor to dry. If it is straightened while wet, pressing may be unnecessary. This is the best means for straightening wool which has been tendered or debated "off-grain". It should not be used on wool crepe. Fabrics that have a napped surface, such as wool broadcloth or some wool flannels, may be changed in appearance. Wool fabrics should always be tested for shrinkage prior to cutting. A simple method of testing is to draw a right angle on the ironing board, place the warp edge along one side and the filling edge along the other side, and hold a stream iron over the fabric. If either edge draws away from the pencil line, the fabric will shrink during steam pressing and it should be shrunk.
References:
[1] N. Hollen and J. Saddler, Textiles, 3rd Edition, MacMillan Company, London (1968).
[2]https://textileinsight.blogspot.com/2014/09/sanforizing-machine-and-process.html
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