500th Published Post
This is the five hundredth published post. The first post was - ArtCloth: Engaging New Visions - and it was published on Thursday, August 26, 2010. Since that time a new post has been compiled and and published every Saturday (except for January due to the Christmas break).
I would like to thank my husband, Dr Ellak I. von Nagy-Felsobuki and CEO of Art Quill & Co Pty Ltd to which Art Quill Studio is its educational sub-division, for his support and tireless hard work in formatting each post in HTML and for ensuring there are no software conflicts. He is an inspiration for me to continue to blog.
I would also like to thank my Followers and those visiting the blogspot for their support.
Thank you.
Marie-Therese
Preamble
This is the one hundredth and second 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
Adjective dyes require a mordant in order to be colorfast. The word “mordant” is derived from the Latin word “mordere”, which translates “to bite”. It was thought that the metal salts (mordants) assisted the dye molecules to bite into the fabric such as silk and wool in order to create a colorfast dye. Madder was the red mordant dye used for dyeing the uniforms of the British Army.
Mordant Dyes.
Generally, the problem with adjective dyes was that they were small in size and so could easily move in and out of the fiber. The metal salt in solution freed the metal ions, which then attached to the dye molecules due to their chemical affinity. This resulted in a large metal complex, which was unable to move out of the voids of the amorphous region of the fiber polymer system. Hence, the metal complex (now a dye in its own right) was trapped and entangled inside the amorphous region, resulting in a washfast, colorfast dye.
Metal complexation of a mordant dye.
Note: Small dye molecules pass freely in and out of the amorphous region of the fiber polymer system. However, if certain metals are added, the dye molecule will bond with the metal to form a much larger dye molecule (the process being called metal complexation). If this occurs inside the amorphous region of the fiber polymer system, the metal complex will be trapped and entangled within this region, thus producing a washfast fabric.
Courtesy of reference [1].
Of course prior to the 17th Century the dyers of the Subcontinent (India and Pakistan) enraptured the Europeans because of their colorful cloth, achieved by their skilful use of mordants.
Mordant dyes can be natural (adjective) and synthetic, with the common thread being that this class of dyes need a mordant in order to make the fabric washfast and colorfast. Synthetic mordant dyes were among the first synthetic dyes that were formulated. Mordant Green 4 was synthesized in 1875 and it is a brownish olive when treated with chromium and yellowish green when treated with iron. In some cases the mordant (i.e. the metal ion) was incorporated in the dye itself in order to secure a particular color. Hence in the mordant dye “Acid Violet 78”, the dye has a chromium atom already incorporated into its structure. The chromium atom in the dye directly bonds to the wool fiber molecule, thereby making the mordant dye washfast.
Mordant Red 80 (C.I. 26565).
Note: It could also be classified as an azoic dye, because it has an azo (-N=N-) link. It was developed in 1899. It is orange brown and soluble in water. When wool is dyed with Mordant Red 80 and is treated with chromium acetate, the end product is a washfast colorfast red dyed wool.
Courtesy of reference [1].
If we label Mordant Red 80 with the letter "D" (for dye) then in the amorphous regions of the wool polymer system, the small dye molecules will link with chromium (from chromium acetate) to produce a much larger sized metal-dye complex that cannot exit the amorphous region of the wool polymer system, since the exit gaps of the fiber polymer system are now far too small in size to allow the larger metal-dye complex passage.
A metal complex (now a dye in its own right) trapped by a bonding mechanism in the voids of the amorphous fiber region. In this example, the “M” is for the metal chromium atom bonded to six Mordant Red 80 dye molecules (D).
Dye coloring as a function of the base colorant, mordent employed and the fabric that is dyed.
Common Mordants and Their Coloring Effect
Mordanting is usually done prior to the dyeing process. The most commonly used mordants are alum, tin, chrome and iron. Yarn must be free from any grease or dirt prior to mordanting, since their presence will hinder absorption in both the mordanting and dyeing processes. Moreover, for beginners it is easy to start by using unbleached natural wool as it simplifies the initial steps in the mordanting process. Wool is wound loosely into skeins prior to mordanting.
The recipes for mordants vary, depending on the color aimed for and the type of fabric being dyed (e.g. linen, cotton and wool etc.) Mordants can be quite toxic and so should be treated as such.
The quantity for each ingredient given below assumes its proportion in relation to a dye bath containing 13 liters (3 gallons) of water. It is important to use the exact quantity of chemicals as excess will damage the yarn.
Alum (aluminium potassium sulfate)
Alum adds brightness and fixes the color of natural dyes. For dyeing wool use 113 g (4 oz) alum with 28 g (1 oz) tartaric acid. For dyeing linen use 113 g (4 oz) alum with 28 g (1 oz) washing soda.
Tin (stannous chloride)
Tin enhances colors, especially reds and yellows. For dyeing wool use 14 g (0.5 oz) tin, with 28 g (1 oz) tartaric acid. For dyeing linen measure out 2 teaspoons of tin.
Chrome (potassium dichromate)
Chrome gives a browny tint to the fabric color. This chemical is extremely sensitive to light and for maximum performance, it must be kept in a tightly sealed container, otherwise it will decompose and so its effectiveness will be greatly diminished. For dyeing with wool, use 14 g (0.5 oz) chrome with 28 g (1 oz) tartaric acid. For dyeing with linen measure out one tablespoon of chrome (slightly more if you are aiming for a deeper tone).
Iron (ferrous sulfate)
Iron darkens the color intensity and it can be added directly into the dye bath. For dyeing all yarns use 28 g (1 oz) tartaric acid with 28 g (1 oz) iron.
Colors that can be obtained using natural dyes: yellow (alum), strong yellow (tin), yellow-green (alum and iron), tan (vinegar). For each color, the mordants are indicated inside the brackets.
Mordanting Wool
Choose a mordant, weigh out the ingredients and dissolve them in a small amount of hot water. Pour this solution in a pan containing the 13 liters of water. Place the wet wool in the pan, making sure the wool in the fully immersed and that there is ample room for the free circulation of the solution. Bring the water slowly to a simmer (which will take about 45 minutes) and then allow it to simmer for another 45 minutes, stirring the solution once or twice in the process. Finer wool, which is more absorbent will only require 25 minutes of additional simmer time. Leave the wool is the solution until it is cool enough to handle, then remove it, squeeze it out gently and rest it by wrapping it in a cloth. Leave it for about 24 hours to allow the mordant to mature in the wool. Yarn that is mordanted using chrome must be kept away from light (i.e. placed in a dark environment).
Mordanting Linen and Cotton
Choose a mordant recipe and measure out the ingredients. Place the wet yarn in a solution of mordant and 13 liters of water and let it simmer for one hour. Allow the yarn to cool naturally and leave it for 24 hours in the solution. Remove it and rinse thoroughly but keep the mordant solution for later use. Dissolve 28 g (1 oz) of tartaric acid and add it to a second pan containing 13 liters of water. Immerse the wet yarn and leave it to simmer for an hour. Let it cool naturally and leave it in the solution for 24 hours before rinsing. Return the yarn back to the first solution and let it soak for 12 hours. Remove and rinse the yarn thoroughly.
Fibers most readily dyed with mordant dyes are natural protein fibers, particularly wool; and sometimes such synthetic fibers as modacrylic and nylon.
Wool dyed with various mordant dyes.
Courtesy of reference [2].
Birch: (1) Leaves with alum mordant; (2) Bark; (3) Bark with iron mordant; (4) Bark with alum mordant.
Courtesy of reference [3].
Elder: (1) Leaves with alum mordant; (2) Bark with iron mordant; (3) Berries; (4) Berries with alum mordant and salt; (5) Berries with alum mordant.
Courtesy of reference [3].
Onion skin: (1) with alum; (2) with iron added.
Courtesy of reference [3].
Pine cones: (1) with alum; (2) with iron added.
Courtesy of reference [3].
Walnut: (1) shrub and husks; (2) with alum mordant.
Courtesy of reference [3].
Dyeing With Mordants
Three methods are used to apply mordant dyes to textile materials.
Chrome Mordant Method
This method of dye application has two stages, namely: (i) Mordanting - the mordant is applied to the textile material (see above); (ii) the mordanted textile material is put in the dye liquor.
The mordant is applied to the textile from an aqueous medium containing the mordant, such as sodium or potassium dichromate, and an acid, such as acetic acid. Mordanting involves boiling the textile material in the aqueous solution containing the mordant for approximately half to three quarters of an hour (see above). The mordanted textile is then transferred to the aqueous solution containing the mordant dye and acid and the temperature raised slowly to the boil. This stage of dyeing can take about 90 minutes to the boil in order to obtain a level dyeing and achieve adequate exhaustion of the dye. During this stage the dye molecule attaches itself to the mordant, which is already in the fiber polymer system and so forms complexes with it, which are called "lakes". The dye is thought to be held in the fiber polymer system by forming a bond with the mordant, which has formed a bond with the fiber polymer. The complex, which is formed with the fiber polymer is relatively large and provide dyeings with good wet-fastness. This is due to the presence of van der Waals' forces, which bind the larger molecules and the presence of hydrogen bonds with the polymer system of the fiber, which prevent the subsequent removal of the dye molecules in aqueous treatments such as in the case of laundering.
Metachrome Method
This is a one stage process in which the dye and the mordant are applied to the fiber simultaneously. This method can only be used with dyes, which do not form the dye mordant complex immediately on coming together; that is, the mordant and dye anions do not form a complex until they have entered the polymer system of the fiber. In fact, the dye complex can be formed in the dye liquor and so care must be taken that this does not occur. (This will give rise to poor rub-fastness). To minimize the formation of the complex in the dye liquor, the mordant dye is added and the textile material treated with the dye liquor and the temperature raised to about 50oC. At this point the mordant is added and the temperature of the dye liquor raised to boil slowly in about 45 minutes and dyeing continued at a boil for approximately 60 minutes. The method of the attachment of the dye to the fiber is the same as for the chrome mordant method (see above).
After Chrome Method
This method involves a two stage process, but which is the reverse of the chrome mordant method. This method involves the application of the dye followed by mordanting. This method involves the use of certain mordant dyes, which are actually acid dyes that can be mordanted. The dyes are applied to the textile material from an aqueous solution, which contains the dye and sodium sulfate. The textile material is treated in this liquor by slowly raising the temperature of the dye liquor to the boil, where it is kept for approximately an hour. At this point, the mordant is added and the temperature maintained at the boil for another 45 minutes to one hour. During this period the dye complexes are formed within the fiber polymer system; the mode of attachment of the dye to the fiber is the same for the chrome mordant method.
Printing With Mordant Dyes
Mordant dyes are rarely used for printing as it is more convenient to print textiles with other classes of dyes.
Properties Of Mordant Dyes
Lightfastness
The lightfastness of mordant dyes are rated approximately 5. The presence of the chromium atom in the dye molecule increases the structural integrity of the dye and so contributes to preventing easy passage out of the polymer fiber complex yielding it very good lightfastness of mordant dyed textile materials. The presence of chromium also adds to the stability of the chromophores embedded in the chrome-dye complex, resulting in added resistance to UV damage.
Washfastness
The washfastness rating of mordant dyes in approximately 4-5. The very good washfastness of textile materials dyed with mordant dyes is due to the large dyed molecules or lakes that are formed within the polymer system of the fiber. These molecules, in addition to being large and so difficult to move through the fiber passages or channels to the outer surface of the fiber, are also held within the amorphous fiber region by hydrogen bonds and van der Waals' forces.
Dull and Limited Range of Colors
There is a limited range of colors available when using mordant dyes and those available, are also relatively dull. It is thought that the presence of the chromium atom is the responsible for both of these short comings.
General Disadvantages in Using Mordant Dyes
Generally there are three major disadvantages in using mordant dyes and these are: (i) color matching is difficult as the process of mordanting means that color is gradually built up rather than controlled; (ii) lengthy period of application is costly and moreover, detrimental to both protein and polyamide fibers; (iii) dichromate salts such as sodium and potassium become pollutants once they are discharged into the sewerage.
Hence mordant dyes are being replaced by premetallized dyes.
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).
[3] Ed. A. Jeffs, W. Martensson and P. North, Creative Crafts Encyclopedia, Equinox (Oxford Ltd) Oxford (1977).
This is the five hundredth published post. The first post was - ArtCloth: Engaging New Visions - and it was published on Thursday, August 26, 2010. Since that time a new post has been compiled and and published every Saturday (except for January due to the Christmas break).
I would like to thank my husband, Dr Ellak I. von Nagy-Felsobuki and CEO of Art Quill & Co Pty Ltd to which Art Quill Studio is its educational sub-division, for his support and tireless hard work in formatting each post in HTML and for ensuring there are no software conflicts. He is an inspiration for me to continue to blog.
I would also like to thank my Followers and those visiting the blogspot for their support.
Thank you.
Marie-Therese
Preamble
This is the one hundredth and second 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
Adjective dyes require a mordant in order to be colorfast. The word “mordant” is derived from the Latin word “mordere”, which translates “to bite”. It was thought that the metal salts (mordants) assisted the dye molecules to bite into the fabric such as silk and wool in order to create a colorfast dye. Madder was the red mordant dye used for dyeing the uniforms of the British Army.
Generally, the problem with adjective dyes was that they were small in size and so could easily move in and out of the fiber. The metal salt in solution freed the metal ions, which then attached to the dye molecules due to their chemical affinity. This resulted in a large metal complex, which was unable to move out of the voids of the amorphous region of the fiber polymer system. Hence, the metal complex (now a dye in its own right) was trapped and entangled inside the amorphous region, resulting in a washfast, colorfast dye.
Note: Small dye molecules pass freely in and out of the amorphous region of the fiber polymer system. However, if certain metals are added, the dye molecule will bond with the metal to form a much larger dye molecule (the process being called metal complexation). If this occurs inside the amorphous region of the fiber polymer system, the metal complex will be trapped and entangled within this region, thus producing a washfast fabric.
Courtesy of reference [1].
Of course prior to the 17th Century the dyers of the Subcontinent (India and Pakistan) enraptured the Europeans because of their colorful cloth, achieved by their skilful use of mordants.
Mordant dyes can be natural (adjective) and synthetic, with the common thread being that this class of dyes need a mordant in order to make the fabric washfast and colorfast. Synthetic mordant dyes were among the first synthetic dyes that were formulated. Mordant Green 4 was synthesized in 1875 and it is a brownish olive when treated with chromium and yellowish green when treated with iron. In some cases the mordant (i.e. the metal ion) was incorporated in the dye itself in order to secure a particular color. Hence in the mordant dye “Acid Violet 78”, the dye has a chromium atom already incorporated into its structure. The chromium atom in the dye directly bonds to the wool fiber molecule, thereby making the mordant dye washfast.
Note: It could also be classified as an azoic dye, because it has an azo (-N=N-) link. It was developed in 1899. It is orange brown and soluble in water. When wool is dyed with Mordant Red 80 and is treated with chromium acetate, the end product is a washfast colorfast red dyed wool.
Courtesy of reference [1].
If we label Mordant Red 80 with the letter "D" (for dye) then in the amorphous regions of the wool polymer system, the small dye molecules will link with chromium (from chromium acetate) to produce a much larger sized metal-dye complex that cannot exit the amorphous region of the wool polymer system, since the exit gaps of the fiber polymer system are now far too small in size to allow the larger metal-dye complex passage.
Dye coloring as a function of the base colorant, mordent employed and the fabric that is dyed.
Common Mordants and Their Coloring Effect
Mordanting is usually done prior to the dyeing process. The most commonly used mordants are alum, tin, chrome and iron. Yarn must be free from any grease or dirt prior to mordanting, since their presence will hinder absorption in both the mordanting and dyeing processes. Moreover, for beginners it is easy to start by using unbleached natural wool as it simplifies the initial steps in the mordanting process. Wool is wound loosely into skeins prior to mordanting.
The recipes for mordants vary, depending on the color aimed for and the type of fabric being dyed (e.g. linen, cotton and wool etc.) Mordants can be quite toxic and so should be treated as such.
The quantity for each ingredient given below assumes its proportion in relation to a dye bath containing 13 liters (3 gallons) of water. It is important to use the exact quantity of chemicals as excess will damage the yarn.
Alum (aluminium potassium sulfate)
Alum adds brightness and fixes the color of natural dyes. For dyeing wool use 113 g (4 oz) alum with 28 g (1 oz) tartaric acid. For dyeing linen use 113 g (4 oz) alum with 28 g (1 oz) washing soda.
Tin (stannous chloride)
Tin enhances colors, especially reds and yellows. For dyeing wool use 14 g (0.5 oz) tin, with 28 g (1 oz) tartaric acid. For dyeing linen measure out 2 teaspoons of tin.
Chrome (potassium dichromate)
Chrome gives a browny tint to the fabric color. This chemical is extremely sensitive to light and for maximum performance, it must be kept in a tightly sealed container, otherwise it will decompose and so its effectiveness will be greatly diminished. For dyeing with wool, use 14 g (0.5 oz) chrome with 28 g (1 oz) tartaric acid. For dyeing with linen measure out one tablespoon of chrome (slightly more if you are aiming for a deeper tone).
Iron (ferrous sulfate)
Iron darkens the color intensity and it can be added directly into the dye bath. For dyeing all yarns use 28 g (1 oz) tartaric acid with 28 g (1 oz) iron.
Colors that can be obtained using natural dyes: yellow (alum), strong yellow (tin), yellow-green (alum and iron), tan (vinegar). For each color, the mordants are indicated inside the brackets.
Mordanting Wool
Choose a mordant, weigh out the ingredients and dissolve them in a small amount of hot water. Pour this solution in a pan containing the 13 liters of water. Place the wet wool in the pan, making sure the wool in the fully immersed and that there is ample room for the free circulation of the solution. Bring the water slowly to a simmer (which will take about 45 minutes) and then allow it to simmer for another 45 minutes, stirring the solution once or twice in the process. Finer wool, which is more absorbent will only require 25 minutes of additional simmer time. Leave the wool is the solution until it is cool enough to handle, then remove it, squeeze it out gently and rest it by wrapping it in a cloth. Leave it for about 24 hours to allow the mordant to mature in the wool. Yarn that is mordanted using chrome must be kept away from light (i.e. placed in a dark environment).
Mordanting Linen and Cotton
Choose a mordant recipe and measure out the ingredients. Place the wet yarn in a solution of mordant and 13 liters of water and let it simmer for one hour. Allow the yarn to cool naturally and leave it for 24 hours in the solution. Remove it and rinse thoroughly but keep the mordant solution for later use. Dissolve 28 g (1 oz) of tartaric acid and add it to a second pan containing 13 liters of water. Immerse the wet yarn and leave it to simmer for an hour. Let it cool naturally and leave it in the solution for 24 hours before rinsing. Return the yarn back to the first solution and let it soak for 12 hours. Remove and rinse the yarn thoroughly.
Fibers most readily dyed with mordant dyes are natural protein fibers, particularly wool; and sometimes such synthetic fibers as modacrylic and nylon.
Courtesy of reference [2].
Courtesy of reference [3].
Courtesy of reference [3].
Courtesy of reference [3].
Courtesy of reference [3].
Courtesy of reference [3].
Dyeing With Mordants
Three methods are used to apply mordant dyes to textile materials.
Chrome Mordant Method
This method of dye application has two stages, namely: (i) Mordanting - the mordant is applied to the textile material (see above); (ii) the mordanted textile material is put in the dye liquor.
The mordant is applied to the textile from an aqueous medium containing the mordant, such as sodium or potassium dichromate, and an acid, such as acetic acid. Mordanting involves boiling the textile material in the aqueous solution containing the mordant for approximately half to three quarters of an hour (see above). The mordanted textile is then transferred to the aqueous solution containing the mordant dye and acid and the temperature raised slowly to the boil. This stage of dyeing can take about 90 minutes to the boil in order to obtain a level dyeing and achieve adequate exhaustion of the dye. During this stage the dye molecule attaches itself to the mordant, which is already in the fiber polymer system and so forms complexes with it, which are called "lakes". The dye is thought to be held in the fiber polymer system by forming a bond with the mordant, which has formed a bond with the fiber polymer. The complex, which is formed with the fiber polymer is relatively large and provide dyeings with good wet-fastness. This is due to the presence of van der Waals' forces, which bind the larger molecules and the presence of hydrogen bonds with the polymer system of the fiber, which prevent the subsequent removal of the dye molecules in aqueous treatments such as in the case of laundering.
Metachrome Method
This is a one stage process in which the dye and the mordant are applied to the fiber simultaneously. This method can only be used with dyes, which do not form the dye mordant complex immediately on coming together; that is, the mordant and dye anions do not form a complex until they have entered the polymer system of the fiber. In fact, the dye complex can be formed in the dye liquor and so care must be taken that this does not occur. (This will give rise to poor rub-fastness). To minimize the formation of the complex in the dye liquor, the mordant dye is added and the textile material treated with the dye liquor and the temperature raised to about 50oC. At this point the mordant is added and the temperature of the dye liquor raised to boil slowly in about 45 minutes and dyeing continued at a boil for approximately 60 minutes. The method of the attachment of the dye to the fiber is the same as for the chrome mordant method (see above).
After Chrome Method
This method involves a two stage process, but which is the reverse of the chrome mordant method. This method involves the application of the dye followed by mordanting. This method involves the use of certain mordant dyes, which are actually acid dyes that can be mordanted. The dyes are applied to the textile material from an aqueous solution, which contains the dye and sodium sulfate. The textile material is treated in this liquor by slowly raising the temperature of the dye liquor to the boil, where it is kept for approximately an hour. At this point, the mordant is added and the temperature maintained at the boil for another 45 minutes to one hour. During this period the dye complexes are formed within the fiber polymer system; the mode of attachment of the dye to the fiber is the same for the chrome mordant method.
Printing With Mordant Dyes
Mordant dyes are rarely used for printing as it is more convenient to print textiles with other classes of dyes.
Properties Of Mordant Dyes
Lightfastness
The lightfastness of mordant dyes are rated approximately 5. The presence of the chromium atom in the dye molecule increases the structural integrity of the dye and so contributes to preventing easy passage out of the polymer fiber complex yielding it very good lightfastness of mordant dyed textile materials. The presence of chromium also adds to the stability of the chromophores embedded in the chrome-dye complex, resulting in added resistance to UV damage.
Washfastness
The washfastness rating of mordant dyes in approximately 4-5. The very good washfastness of textile materials dyed with mordant dyes is due to the large dyed molecules or lakes that are formed within the polymer system of the fiber. These molecules, in addition to being large and so difficult to move through the fiber passages or channels to the outer surface of the fiber, are also held within the amorphous fiber region by hydrogen bonds and van der Waals' forces.
Dull and Limited Range of Colors
There is a limited range of colors available when using mordant dyes and those available, are also relatively dull. It is thought that the presence of the chromium atom is the responsible for both of these short comings.
General Disadvantages in Using Mordant Dyes
Generally there are three major disadvantages in using mordant dyes and these are: (i) color matching is difficult as the process of mordanting means that color is gradually built up rather than controlled; (ii) lengthy period of application is costly and moreover, detrimental to both protein and polyamide fibers; (iii) dichromate salts such as sodium and potassium become pollutants once they are discharged into the sewerage.
Hence mordant dyes are being replaced by premetallized dyes.
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).
[3] Ed. A. Jeffs, W. Martensson and P. North, Creative Crafts Encyclopedia, Equinox (Oxford Ltd) Oxford (1977).
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