Preamble
This is the one hundredth and tenth 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!
Introduction
The name 'vat' was derived from the large wooden vessel from which vat dyes were first applied. Vat dyes generate textile materials with the best color-fastness of all dyes in common use. The fibers most readily colored with vat dyes are the natural and man-made cellulosic fibers.
Some vat dyes.
A vat dyed textile.
Courtesy of tracymaccabestewart.com
Vat dyes belong to the chemical family of anthraquinone dyes, which were first synthesized in 1901. The vat dyes are mostly sold in the oxidized form, sometimes as dry solids, but more often as aqueous paste. Perhaps the most well known vat dye is indigotin (indigo).
Vat Green 8, C.I. 71050.
Note: An anthraquinone type vat dye, which illustrates the enormous size of vat dye molecules.
Courtesy of reference[1].
The vat dyes are large flat molecules insoluble in water and so in this form unsuitable for dyeing. Firstly, vat dyes need to be made soluble and this is achieved with a reduction reaction using sodium hydrosulfite under strong alkali conditions in the absence of air in order to produce the leuco form of the vat dye (normally a hydroxide form). This form is also a flat linear molecule but in this form is water-soluble. The leuco form generally is white or colorless. The soluble leuco form is then applied to the cotton fiber from an alkaline reductive bath. When the alkali on the fiber is neutralized, using acetic acid, the oxygen in the air oxidizes the dye back to its insoluble form.
Oxidation returns the Vat dye into the insoluble form.
Note: The leuco form is colorless and soluble in water, whereas the oxidized form has color and is insoluble in water. Also, this diagram highlights that many vat dyes have an anthraquinone skeleton.
Courtesy of reference[2].
Dyeing with Vat Dyes
The application of vat dyes to cellulosic materials occurs in five stages. We shall deal with each stage separately.
(i) Aqueous Dispersion: The insoluble vat dye is dispersed in water.
(ii) Vatting: This step involves the chemical reduction of the vat dye to produce the soluble, reduced or the leuco form of the dye. This is achieved by sodium hydrosulfite, sodium hydroxide and water. The sodium hydrosulfite chemically reduces the vat dye in the alkaline conditions, created by the presence of sodium hydroxide. Note: Vatting stage also temporarily alters the original color of the dye.
(iii) Absorption of Dye Molecules by the Fiber: The vatted dyed molecules are substantive to the cellulosic textile material that is introduced into the dye liquor. To achieve adequate exhaustion, an electrolyte is added to the dye liquor and the temperature may be increased depending on the specific vat dye. The application of the dye molecule to the fiber occurs at temperatures specific to a particular vat dye and usually occurs between 20oC to 60oC. The addition of an electrolyte alters the equilibrium of the dye liquor so as to increase the substantivity of the dye molecule to the fiber polymer system. During this stage of the dye application, the textile material must be kept immersed in the dye liquor to prevent premature oxidation of the leuco compound.
(iv) Re-Oxidation of Dye Molecules within the Fiber: Once within the fiber polymer system, the leuco form of the vat dye has to be oxidized and converted to its original color and to its original insoluble form of the dye. Oxidation of the leuco compound can be achieved by atmospheric oxygen, although this is somewhat slow. In practice, a mild oxidizing reagent, such as sodium perborate, is used to convert the soluble leuco form into the original insoluble vat dye.
(v) Soaping-Off Vat Dyes: During stage (iv) some of the vat will be deposited on the surface of the fiber, and the surface dye must be removed to prevent poor rub-fastness as well as to prevent a possible change of shade which would occur as the surface dye becomes removed over a period of time. Soaping-off, which involves the boiling of the dyed material in a liquor containing some suitable detergent, removes the surface dyes.
Note: The size of the vat dyes and the way they become entangled in the amorphous regions of the fiber polymer system, their substantivity for the fiber polymer system, the weak van der Waals forces of attraction, and their insolubility in water, all complement one another to prevent loss of dye during the soaping-off process.
Printing with Vat Dyes
Printing of textile materials with dyes is achieved through the preparation of a paste with stabilized reduced vat dye. The fabric is printed with the design and dye fixation is obtained by steaming to achieve adequate penetration of the fiber polymer system by the dye molecule. The textile material is then oxidized and soaped-off as in the case of dyeing.
When the fabric is removed from the dye bath, generally the vat dye inside the fibre is quite wash-fast (since they are insoluble in water), whereas the dye on the surface of the fiber is not so fixed and can be easily rubbed off. Soaping – washing the dyed fabric in near-boiling soapy water – removes the excess dye molecules from the surface as well as promoting aggregation and orientation of the dye molecules within the fibers. You should note that some vat dyes are sensitive to ultraviolet light, whereas others have excellent light fastness.
Properties of Vat Dyes
Light-Fastness
The light-fastness of vat dyes rates about 7, which translates as excellent. This is attributed to the stable electronic configuration of the vat dye chromophores to resist the degrading effects of UV sunlight. The presence of numerous very electronically stable benzene rings contributes to the vat dyes resistance to UV sunlight degradation.
Wash-Fastness
The wash-fastness of vat dyes rates between 4-5, which translates as excellent. The reason for this is simple. The vat dyes are very large molecules and so once they entered via enlarged voids (due to heating) of the amorphous regions of fiber polymer system, on cooling these entry/exit voids shrink in size, entrapping and tangling the vat dyes in this region. This is further assisted by weak van der Waals forces of attraction that the vat dyes have for the fiber molecules. Laundering fading is further resisted since vat dyes are insoluble in water and so repel water rather be attracted to it.
Cost of Vat Dyes
Vat dyes have always been very expensive compared with other dye classes and are invariably used when good fastness properties are required.
Solubilized Vat Dyes
As with sulfur dyes, the solubilized form of the vat dye has been developed. This has made vat dyes easier to handle and results in more level dyeing.
References:
[1] E.P.G. Gohl and L.D. Vilensky, Textile Science, Longman Cheshire, Melbourne (1989).
[2] A Fritz and J. Cant, Consumer Textiles, Oxford University Press, Melbourne (1986).
This is the one hundredth and tenth 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!
Introduction
The name 'vat' was derived from the large wooden vessel from which vat dyes were first applied. Vat dyes generate textile materials with the best color-fastness of all dyes in common use. The fibers most readily colored with vat dyes are the natural and man-made cellulosic fibers.
Courtesy of tracymaccabestewart.com
Vat dyes belong to the chemical family of anthraquinone dyes, which were first synthesized in 1901. The vat dyes are mostly sold in the oxidized form, sometimes as dry solids, but more often as aqueous paste. Perhaps the most well known vat dye is indigotin (indigo).
Note: An anthraquinone type vat dye, which illustrates the enormous size of vat dye molecules.
Courtesy of reference[1].
The vat dyes are large flat molecules insoluble in water and so in this form unsuitable for dyeing. Firstly, vat dyes need to be made soluble and this is achieved with a reduction reaction using sodium hydrosulfite under strong alkali conditions in the absence of air in order to produce the leuco form of the vat dye (normally a hydroxide form). This form is also a flat linear molecule but in this form is water-soluble. The leuco form generally is white or colorless. The soluble leuco form is then applied to the cotton fiber from an alkaline reductive bath. When the alkali on the fiber is neutralized, using acetic acid, the oxygen in the air oxidizes the dye back to its insoluble form.
Note: The leuco form is colorless and soluble in water, whereas the oxidized form has color and is insoluble in water. Also, this diagram highlights that many vat dyes have an anthraquinone skeleton.
Courtesy of reference[2].
Dyeing with Vat Dyes
The application of vat dyes to cellulosic materials occurs in five stages. We shall deal with each stage separately.
(i) Aqueous Dispersion: The insoluble vat dye is dispersed in water.
(ii) Vatting: This step involves the chemical reduction of the vat dye to produce the soluble, reduced or the leuco form of the dye. This is achieved by sodium hydrosulfite, sodium hydroxide and water. The sodium hydrosulfite chemically reduces the vat dye in the alkaline conditions, created by the presence of sodium hydroxide. Note: Vatting stage also temporarily alters the original color of the dye.
(iii) Absorption of Dye Molecules by the Fiber: The vatted dyed molecules are substantive to the cellulosic textile material that is introduced into the dye liquor. To achieve adequate exhaustion, an electrolyte is added to the dye liquor and the temperature may be increased depending on the specific vat dye. The application of the dye molecule to the fiber occurs at temperatures specific to a particular vat dye and usually occurs between 20oC to 60oC. The addition of an electrolyte alters the equilibrium of the dye liquor so as to increase the substantivity of the dye molecule to the fiber polymer system. During this stage of the dye application, the textile material must be kept immersed in the dye liquor to prevent premature oxidation of the leuco compound.
(iv) Re-Oxidation of Dye Molecules within the Fiber: Once within the fiber polymer system, the leuco form of the vat dye has to be oxidized and converted to its original color and to its original insoluble form of the dye. Oxidation of the leuco compound can be achieved by atmospheric oxygen, although this is somewhat slow. In practice, a mild oxidizing reagent, such as sodium perborate, is used to convert the soluble leuco form into the original insoluble vat dye.
(v) Soaping-Off Vat Dyes: During stage (iv) some of the vat will be deposited on the surface of the fiber, and the surface dye must be removed to prevent poor rub-fastness as well as to prevent a possible change of shade which would occur as the surface dye becomes removed over a period of time. Soaping-off, which involves the boiling of the dyed material in a liquor containing some suitable detergent, removes the surface dyes.
Note: The size of the vat dyes and the way they become entangled in the amorphous regions of the fiber polymer system, their substantivity for the fiber polymer system, the weak van der Waals forces of attraction, and their insolubility in water, all complement one another to prevent loss of dye during the soaping-off process.
Printing with Vat Dyes
Printing of textile materials with dyes is achieved through the preparation of a paste with stabilized reduced vat dye. The fabric is printed with the design and dye fixation is obtained by steaming to achieve adequate penetration of the fiber polymer system by the dye molecule. The textile material is then oxidized and soaped-off as in the case of dyeing.
When the fabric is removed from the dye bath, generally the vat dye inside the fibre is quite wash-fast (since they are insoluble in water), whereas the dye on the surface of the fiber is not so fixed and can be easily rubbed off. Soaping – washing the dyed fabric in near-boiling soapy water – removes the excess dye molecules from the surface as well as promoting aggregation and orientation of the dye molecules within the fibers. You should note that some vat dyes are sensitive to ultraviolet light, whereas others have excellent light fastness.
Properties of Vat Dyes
Light-Fastness
The light-fastness of vat dyes rates about 7, which translates as excellent. This is attributed to the stable electronic configuration of the vat dye chromophores to resist the degrading effects of UV sunlight. The presence of numerous very electronically stable benzene rings contributes to the vat dyes resistance to UV sunlight degradation.
Wash-Fastness
The wash-fastness of vat dyes rates between 4-5, which translates as excellent. The reason for this is simple. The vat dyes are very large molecules and so once they entered via enlarged voids (due to heating) of the amorphous regions of fiber polymer system, on cooling these entry/exit voids shrink in size, entrapping and tangling the vat dyes in this region. This is further assisted by weak van der Waals forces of attraction that the vat dyes have for the fiber molecules. Laundering fading is further resisted since vat dyes are insoluble in water and so repel water rather be attracted to it.
Cost of Vat Dyes
Vat dyes have always been very expensive compared with other dye classes and are invariably used when good fastness properties are required.
Solubilized Vat Dyes
As with sulfur dyes, the solubilized form of the vat dye has been developed. This has made vat dyes easier to handle and results in more level dyeing.
References:
[1] E.P.G. Gohl and L.D. Vilensky, Textile Science, Longman Cheshire, Melbourne (1989).
[2] A Fritz and J. Cant, Consumer Textiles, Oxford University Press, Melbourne (1986).
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