Preamble
This is the one hundredth and fourth 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
Dyes can be classified according to their application (e.g. disperse dyes), their nature (e.g. acidic dyes) and their structure (e.g. azoic dyes). The first classification is what art and craft dyers gravitate to, whereas the last is what chemists prefer.
It should be noted that a mordant dye, a basic dye and an acidic dye could also be classified as an azoic dye - even though they are structurally different - so long as all three dyes contain at least one azo group (ie -N=N-) in their chemical make-up. However, not all mordant, basic and acidic dyes contain azo links and so in these cases, they could not be classified as an azoic dye.
Azoic dyes are also called naphthol dyes, ice colors or developed colors. They are labelled naphthol since they also contain a naphthol group. For example, the azoic dye, Congo Red, contains two azo linkages (-N=N-) separated by a di-phenyl group, with the opposite linkages attached to a naphthol group (see below).
White silk satin printed with azoic dyes.
Typically azoic dyes can be formed inside the fiber polymer systems. Firstly, a colorless component – naphthol - is dyed into the fabric polymer system and since this component is a small molecule it is easily absorbed into the hydrophilic fibers. Nitrous acid is added which reacts with the naphthol to form a highly reactive intermediate called a diazonium ion, which when added to a phenolic compound will yield a highly colored dye within the fiber.
Azoic dyeing takes place under cold conditions in order to prevent the production of undesirable side products. Levelness is a problem for azoic dyeing since it is heavily dependent on the even or uniform coverage of colorless components during the dyeing process. The dyeing generally produces bright and wash fast fabrics (especially reds and oranges). However, care must be taken to wash off any dyes formed on the fiber surface to prevent poor rubbing fastness.
Azoic dyes are generally used on man-made and natural cellulosic fibers (e.g. cotton, viscose etc.) and on silks, and in particular, they are used in batik dyeing. They are gradually being restricted to specialist dyeing applications.
Dyeing With Azoic Dyes
Coloring textile materials with azoic dyes involves the reaction with the fiber polymer system of the two components, which constitutes the azoic dye, namely, naphthol (also called the coupling component) and the diazo component (also called the base). Dyeing or printing with azoic dyes is therefore a multi-stage process.
In order to clarify this complex dyeing process let us follow the formation of Congo Red within the amorphous regions of the textile material. Congo Red is an azoic dye that is red in alkali and blue in an acid solution.
The first stage of dyeing with azoic dyes is called naphtholation, which involves dissolving 4-aminonaphthalene-1-sulfonic acid in water using sodium hydroxide (NaOH). The fiber is impregnated with this solution of naphthol. To assist penetration into the amorphous region of the fiber polymer system, a temperature of 80-85oC is used for viscose, but with cotton, room temperature is adequate. The impregnated textile materials are passed through rollers to remove excess solution from the material.
Stage 1: Chemical formula and structure of 4-aminonaphthalene-1-sulfonic acid.
Note: This naphthol molecule is firstly impregnated in the fiber polymer system.
Courtesy of reference [1].
The second stage of azoic dyeing, called diazotization involves the preparation of a diazo component by converting this component to a soluble diazonium salt, using sodium nitrite (NaNO2) and hydrochloric acid, which generates nitrous acid (HONO). This then reacts with 4,4’-benzidine to yield a diazonium salt. Diazonium salts are fairly unstable and so to decrease their reactivity, ice is usually added to the dye liquor.
Stage 2: A reactive species called a diazonium salt is produced.
Note: The 4,4’-benzidine reacts with nitrous acid to produce a diazonium salt. Only the cation of the salt is shown since the corresponding anion of this salt is in solution and so is not attached to the cation.
Courtesy of reference [1].
Once the fabric has been treated with naphthol it is passed through a liquor containing the diazonium salt to create a reaction that will generate the Congo Red dye in the amorphous region of the textile materials. It is at this stage that the –N=N- or azo link is formed which is the chromophore of the dye.
Stage 3: Formation of the Congo Red dye (bottom molecule).
Note: The naphthol molecules are shown on the left and right side of the diazonium salt. Both naphthol and diazonium salt react in the amorphous region of the fiber polymer system and on the surface to form an azoic dye called Congo Red. This reaction is referred to as coupling, since it couples the naphthol to the diazonium salt to produce the azoic dye (which is characterized by the azo links –N=N-).
Courtesy of reference [1].
It should be noted that the coupling reaction should occur in the amorphous regions of the fiber polymer system. Nevertheless, it is inevitable the coupling reaction will also occur on the surface of the fiber. The removal of the dye on the surface is essential, since azoic dyes are insoluble and unless removed, the textile materials will have poor rub-fastness. This removal is further enhanced by a thorough final rinse of the dyed material. Care must be taken at each stage of the dyeing process, that most of the dye formation occurs within the fiber polymer system and not on its surface.
Printing with Azoic Dyes
The application of azoic dye by printing is similar to that of dyeing except that the fabric impregnated with the coupling component features the printed design. This is followed by the application of the diazonium salt to produce the insoluble azoic dye. As in dyeing, care must be taken that the insoluble dye is formed within the fiber polymer system in order to reduce significantly the possibility of poor rub-fastness.
Properties of Azoic Dyes
Light Fastness
Dyes and printed azoic dyed textile materials have very good to excellent light fastness with ratings of about 6-7, which is due to the stable electronic configuration of its chromophores, which can resist very prolonged exposure to UV sunlight.
Wash Fastness
Wash fastness of azoic dyes is about 4-5, which translates as very good wash fastness of azoic dye and printed textile materials, which is due to the fact that azoic dyes are water insoluble.
Bright Colors
Azoic dyes are characterized by their very bright red and orange colors. Hence these dyes absorb all the incident white light, except light with the wavelength of red and orange.
Rub Fastness
At times azoic dyed and printed textile materials suffer from poor rub fastness (see above). It is important that after dyeing/printing the rinsing stage usually involves a soaping off using a detergent.
If all stages of azoic dyeing and printing are carefully controlled and appropriate rinse off is invoked, poor rub fastness is unlikely to occur.
Blinding
At times azoic dyes may cause a matt or delustered effect. This effect, called blinding, is more common on viscose than on cotton. It is thought that blinding occurs due to incident light becoming more scattered because of the uneven distribution of dye molecules within the amorphous regions of the fiber polymer system. Dye molecules in this region are lumped together or aggregated, and it is this aggregation that causes a greater deal of scattering. Its effect is greater in viscose than in cotton, in that the former has a higher percentage of amorphous regions, than the latter.
References:
[1] A. Fritz and J. Cant, Consumer Textiles, Oxford University Press, Melbourne (1986).
[2] E.P.G. Gohl and L.D. Vilensky, Textile Science, Longman Cheshire, Melbourne (1989).
This is the one hundredth and fourth 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
Dyes can be classified according to their application (e.g. disperse dyes), their nature (e.g. acidic dyes) and their structure (e.g. azoic dyes). The first classification is what art and craft dyers gravitate to, whereas the last is what chemists prefer.
It should be noted that a mordant dye, a basic dye and an acidic dye could also be classified as an azoic dye - even though they are structurally different - so long as all three dyes contain at least one azo group (ie -N=N-) in their chemical make-up. However, not all mordant, basic and acidic dyes contain azo links and so in these cases, they could not be classified as an azoic dye.
Azoic dyes are also called naphthol dyes, ice colors or developed colors. They are labelled naphthol since they also contain a naphthol group. For example, the azoic dye, Congo Red, contains two azo linkages (-N=N-) separated by a di-phenyl group, with the opposite linkages attached to a naphthol group (see below).
Typically azoic dyes can be formed inside the fiber polymer systems. Firstly, a colorless component – naphthol - is dyed into the fabric polymer system and since this component is a small molecule it is easily absorbed into the hydrophilic fibers. Nitrous acid is added which reacts with the naphthol to form a highly reactive intermediate called a diazonium ion, which when added to a phenolic compound will yield a highly colored dye within the fiber.
Azoic dyeing takes place under cold conditions in order to prevent the production of undesirable side products. Levelness is a problem for azoic dyeing since it is heavily dependent on the even or uniform coverage of colorless components during the dyeing process. The dyeing generally produces bright and wash fast fabrics (especially reds and oranges). However, care must be taken to wash off any dyes formed on the fiber surface to prevent poor rubbing fastness.
Azoic dyes are generally used on man-made and natural cellulosic fibers (e.g. cotton, viscose etc.) and on silks, and in particular, they are used in batik dyeing. They are gradually being restricted to specialist dyeing applications.
Dyeing With Azoic Dyes
Coloring textile materials with azoic dyes involves the reaction with the fiber polymer system of the two components, which constitutes the azoic dye, namely, naphthol (also called the coupling component) and the diazo component (also called the base). Dyeing or printing with azoic dyes is therefore a multi-stage process.
In order to clarify this complex dyeing process let us follow the formation of Congo Red within the amorphous regions of the textile material. Congo Red is an azoic dye that is red in alkali and blue in an acid solution.
The first stage of dyeing with azoic dyes is called naphtholation, which involves dissolving 4-aminonaphthalene-1-sulfonic acid in water using sodium hydroxide (NaOH). The fiber is impregnated with this solution of naphthol. To assist penetration into the amorphous region of the fiber polymer system, a temperature of 80-85oC is used for viscose, but with cotton, room temperature is adequate. The impregnated textile materials are passed through rollers to remove excess solution from the material.
Note: This naphthol molecule is firstly impregnated in the fiber polymer system.
Courtesy of reference [1].
The second stage of azoic dyeing, called diazotization involves the preparation of a diazo component by converting this component to a soluble diazonium salt, using sodium nitrite (NaNO2) and hydrochloric acid, which generates nitrous acid (HONO). This then reacts with 4,4’-benzidine to yield a diazonium salt. Diazonium salts are fairly unstable and so to decrease their reactivity, ice is usually added to the dye liquor.
Note: The 4,4’-benzidine reacts with nitrous acid to produce a diazonium salt. Only the cation of the salt is shown since the corresponding anion of this salt is in solution and so is not attached to the cation.
Courtesy of reference [1].
Once the fabric has been treated with naphthol it is passed through a liquor containing the diazonium salt to create a reaction that will generate the Congo Red dye in the amorphous region of the textile materials. It is at this stage that the –N=N- or azo link is formed which is the chromophore of the dye.
Note: The naphthol molecules are shown on the left and right side of the diazonium salt. Both naphthol and diazonium salt react in the amorphous region of the fiber polymer system and on the surface to form an azoic dye called Congo Red. This reaction is referred to as coupling, since it couples the naphthol to the diazonium salt to produce the azoic dye (which is characterized by the azo links –N=N-).
Courtesy of reference [1].
It should be noted that the coupling reaction should occur in the amorphous regions of the fiber polymer system. Nevertheless, it is inevitable the coupling reaction will also occur on the surface of the fiber. The removal of the dye on the surface is essential, since azoic dyes are insoluble and unless removed, the textile materials will have poor rub-fastness. This removal is further enhanced by a thorough final rinse of the dyed material. Care must be taken at each stage of the dyeing process, that most of the dye formation occurs within the fiber polymer system and not on its surface.
Printing with Azoic Dyes
The application of azoic dye by printing is similar to that of dyeing except that the fabric impregnated with the coupling component features the printed design. This is followed by the application of the diazonium salt to produce the insoluble azoic dye. As in dyeing, care must be taken that the insoluble dye is formed within the fiber polymer system in order to reduce significantly the possibility of poor rub-fastness.
Properties of Azoic Dyes
Light Fastness
Dyes and printed azoic dyed textile materials have very good to excellent light fastness with ratings of about 6-7, which is due to the stable electronic configuration of its chromophores, which can resist very prolonged exposure to UV sunlight.
Wash Fastness
Wash fastness of azoic dyes is about 4-5, which translates as very good wash fastness of azoic dye and printed textile materials, which is due to the fact that azoic dyes are water insoluble.
Bright Colors
Azoic dyes are characterized by their very bright red and orange colors. Hence these dyes absorb all the incident white light, except light with the wavelength of red and orange.
Rub Fastness
At times azoic dyed and printed textile materials suffer from poor rub fastness (see above). It is important that after dyeing/printing the rinsing stage usually involves a soaping off using a detergent.
If all stages of azoic dyeing and printing are carefully controlled and appropriate rinse off is invoked, poor rub fastness is unlikely to occur.
Blinding
At times azoic dyes may cause a matt or delustered effect. This effect, called blinding, is more common on viscose than on cotton. It is thought that blinding occurs due to incident light becoming more scattered because of the uneven distribution of dye molecules within the amorphous regions of the fiber polymer system. Dye molecules in this region are lumped together or aggregated, and it is this aggregation that causes a greater deal of scattering. Its effect is greater in viscose than in cotton, in that the former has a higher percentage of amorphous regions, than the latter.
References:
[1] A. Fritz and J. Cant, Consumer Textiles, Oxford University Press, Melbourne (1986).
[2] E.P.G. Gohl and L.D. Vilensky, Textile Science, Longman Cheshire, Melbourne (1989).
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