Preamble
This is the one hundredth and one 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
Indigo is a vat dye and is extracted from the indigo plant.
The indigo plant is not useful for dyeing unless the dyer knows how it must be prepared before it is used. This procedure is complex, so dyers are advised to purchase the dye stuff in powdered form. Powdered indigo had added to it chemicals necessary to render it soluble in water with the use of sodium hydrosulfite as a reducing agent. In other words, the characteristic property of these insoluble dyes is that they can be made soluble using a reduction reaction. That is, they can be made to undergo a chemical reaction in the absence of air which changes the dye into a water soluble form. This soluble form is called "Leuco" and it is white or colorless, flat and a linear molecule in shape.
Slide 1: The colorless soluble form (left) and colored insoluble form (right) of Indigotin (commonly called indigo).
The availability of good, fast blues is important to dyers and moreover, to natural dyers. The powdered dyestuff can be expensive but a little goes a long way.
Today's post solely focusses on this one very import natural dye.
Chemicals and Equipment
Two chemicals are needed to make an indigo bath using the recipe given below. They are: sodium hydrosulfide (commonly known as Hydros) and sodium hydroxide (commonly known as Lye).
Both chemical are poisonous, very strong and dangerous if inhaled or splashed on the skin. Always use rubber gloves when dyeing with indigo and take great care when cleaning up. Always add chemical to a body of water and never add water to a body of chemicals since in the latter process stuttering may occur splattering toxic chemicals over you. Never stir the water into the dry chemical as this produces toxic fumes.
The basic chemicals required are hydros, lye and powdered indigo.
Powdered Indigo.
When ordering powdered indigo, specify that you do not want "synthetic indigo". Genuine powdered indigo is treated with chemicals to make it suitable to use with the recipe given below.
The equipment required is modest: a small enamel pan with a lid, two large covered jars (e.g. pickle jars), several stirrers, measuring cups, measuring spoons, a thermometer, dyepot and fabric or fiber to be dyed.
Recipe[1]
The following three mixtures are made up before the actual dyeing begins: Solution 1, Solution 2, and the Indigo Stock Solution.
Solution 1 - Lye Solution:
To one pint of water in a quart jar (0.5 litre in a one litre jar), slowly add one-third of a cup (70 ml) of lye. Stir carefully. Cover the jar with a lid, label it, and set it aside. (This lye solution is strongly alkaline and becomes quite hot, so wear gloves when preparing it or the jar will be too hot to hold.) Solution 1 will keep for three or four days, after which time it loses strength.
Solution 2 - Hydros Solution:
To one pint of water in a quart jar (0.5 litre in a one litre jar) slowly add 6 tablespoons (80 ml) of hydros. Stir carefully until the chemical is dissolved. This mixture is quite foul-smelling, so cover the jar tightly and then label it. It would also be advisable to do it in a well ventilated area. Before you set it aside, you can wrap it in a plastic bag to diminish the odor. Hydros is the reducing agent. It reduces the indigo by removing the oxygen from the indigo bath.
Indigo Stock Solution:
0.5 of a cup (120 ml) of Solution 1 (lye).
0.5 of a cup (120 ml) of Solution 2 (hydros).
3-4 tablespoons (45 - 60 ml) of powdered non-synthetic indigo.
You will need the indigo stock solution (as prepared above) plus more of Solution 2, hydros.
Recipe:
Heat 4 gallons (18 litres) of water to 120oF or 48oC in the dyepot. Then add 4 tablespoons (60 ml) of hydros, Solution 2, to remove the oxygen present in the water. STIR THIS Gently, if at all, because you do not want to incorporate even more oxygen into the solution! It may be sufficient to merely tip the covered dyepot gently back and forth to distribute the hydros. Now let the water and hydros stand, covered for 10 to 15 minutes to allow it to settle. Next add 4 to 8 tablespoons (60 - 120 ml) of the indigo stock solution. (Using the smaller amount will yield light blues on 1 pound (453 g) of fiber, while the large amount will give medium to dark blue with the same amount of fiber. Cover the bath, and again allow it to sit undisturbed for 20 to 30 minutes to allow the chemicals and indigo to settle. During this time the temperature should be maintained at 120oF or 48oC. You can wrap an old blanket around the dyepot. The temperature may fall a few degrees, but this is all right as long as it does not exceed 120o or 48oC. The bath will now appear to be a yellowish green. This is normal.
It is most important to remember if you feel uncomfortable to carry out this recipe, seek a very experienced dyer who can walk you through this process safely until you have mastered it. THIS IS A MANDATORY STEP FOR NOVICE DYERS.
Dyeing with Indigo
Enter the wet fiber by easing it into the dyepot. Take care not to plunge it in, thereby introducing bubbles (i.e. oxygen). Once the fiber is in, replace the lid and put the dyepot on the heat. Always keep the temperature below 120oF or 48oC. This is a conservative figure: some dyers consider a temperature of 140oF or 60oC safe, but novice dyers should stick to the lower temperatures. Allow the first skein (ie. a length of thread or yarn or cloth, loosely coiled and knotted) to remain in the bath for 20 to 30 minutes. Take out the fiber and oxidize it.
Oxidation Process:
This is what turns the fiber blue, or actually, more blue. Hold the dripping skein OVER A BUCKET (so as not to introduce additional oxygen to the bath) and allow it to drip for several minutes. Within 30 to 60 seconds it will turn blue, a color much more definite than it was in the dyepot.
Indigo Mini Skein 13 oz 368g.
Turn the skein one way and then another so all of it is oxidized. If the color is satisfactory, hang the skein up to drip and label it (first dip etc.) It may be re-dipped later on or, if you want a dark blue, returned to the dyepot immediately. Some dyers claim stronger blues can be achieved if the indigo fibers are oxidised in sunlight, outdoors, for ten to twenty minutes between dips.
Control of Color
The color given by an indigo bath is governed by the amount of stock solution used, the time the fiber is in the bath, and the number of dips. As a dyer gains experience, the colors can be predicted with a fair degree of accuracy, based on previous records. Indigo blues are beautiful as they are, but extremely handsome when topped with strong yellows to produce greens, Experiment! No other dyestuff is quite so time-consuming and yet so rewarding.
Indigo Blue Lace Dress.
Neutralizing
After each skein has been removed from its final dip, it must be neutralized, because it is strongly alkaline. To neutralize the skein the following steps should be invoked:
(i) Rinse the indigo-dyed fiber in lukewarm water to which one cup (240 ml) of vinegar has been added for each pound (453 g) of fiber.
(ii) Rinse next in cool water.
(iii) Rinse a third time in a lukewarm bath using a non-detergent soap.
(iv) Rinse a fourth time in clear, cool water and hang to dry.
Drying:
To avoid streaking indigo skeins, turn the fiber around often as it is drying. This prevents excess moisture from dripping onto one part of the skein. Drape over a plastic-covered rod or plastic clothesline. The dye might stain a painted wooden railing on a porch or fence.
Disposal of Indigo Bath
Since lye and hydros in the indigo bath are strongly alkaline, it will not harm the plumbing to pour it down the sink. After all, many people use lye to unclog drains. However, the indigo solution is messy; its purple slime clings to whatever it touches. Rural dyers with septic systems may wish to dispose of an indigo bath by digging a hole and pouring it into the ground in a spot where children and animals cannot get to. For city folk it is always best to have a conversation with your local council environmental officer.
Cleaning Equipment
All equipment used in indigo dyeing must be carefully cleaned, as even minute traces of the blue residue will spoil subsequent non-indigo baths. Throw stirrers away unless they are glass or plastic. Scrub all utensils with warm water and detergent soap. Then rinse them with a chlorine solution (i.e. a mild bleach solution) followed by a clear water rinse.
Bottoming and Topping with Indigo
Indigo-dyed fibers can be over-dyed with other dyestuff to obtain good greens and already dyed yellows can be made green with subsequent dips in the indigo bath. "Topping" usually refers to the process of covering a light shade, such as yellow, with a darker one, such as blue. "Bottoming" is the reverse: the dark shade is dyed first and the light one goes on top. It is a matter of personal preference which method you use to obtain greens (or any other colors) from indigo. The equality of the resulting color depends on the clarity of the yellow dye. Goldenrod yellows tend to give bluish-greens when topped with indigo; the colors are unique and extremely attractive. Using indigo dyes and other colored dyes will yield colors ranging from turquoise to a variety of navy and dark blues. The turquoise can be made using goldenrod yellow topped with indigo. Indigo dyers are passionate about creating new hues; some have topped soft dogwood rose-greys with indigo for purple heather effects.
Indigo jungle maxi dress.
Reference:
[1] K.L. Casselman, Craft of the Dyer, University of Toronto Press, Toronto (1980).
This is the one hundredth and one 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
Indigo is a vat dye and is extracted from the indigo plant.
The indigo plant is not useful for dyeing unless the dyer knows how it must be prepared before it is used. This procedure is complex, so dyers are advised to purchase the dye stuff in powdered form. Powdered indigo had added to it chemicals necessary to render it soluble in water with the use of sodium hydrosulfite as a reducing agent. In other words, the characteristic property of these insoluble dyes is that they can be made soluble using a reduction reaction. That is, they can be made to undergo a chemical reaction in the absence of air which changes the dye into a water soluble form. This soluble form is called "Leuco" and it is white or colorless, flat and a linear molecule in shape.
The availability of good, fast blues is important to dyers and moreover, to natural dyers. The powdered dyestuff can be expensive but a little goes a long way.
Today's post solely focusses on this one very import natural dye.
Chemicals and Equipment
Two chemicals are needed to make an indigo bath using the recipe given below. They are: sodium hydrosulfide (commonly known as Hydros) and sodium hydroxide (commonly known as Lye).
Both chemical are poisonous, very strong and dangerous if inhaled or splashed on the skin. Always use rubber gloves when dyeing with indigo and take great care when cleaning up. Always add chemical to a body of water and never add water to a body of chemicals since in the latter process stuttering may occur splattering toxic chemicals over you. Never stir the water into the dry chemical as this produces toxic fumes.
The basic chemicals required are hydros, lye and powdered indigo.
When ordering powdered indigo, specify that you do not want "synthetic indigo". Genuine powdered indigo is treated with chemicals to make it suitable to use with the recipe given below.
The equipment required is modest: a small enamel pan with a lid, two large covered jars (e.g. pickle jars), several stirrers, measuring cups, measuring spoons, a thermometer, dyepot and fabric or fiber to be dyed.
Recipe[1]
The following three mixtures are made up before the actual dyeing begins: Solution 1, Solution 2, and the Indigo Stock Solution.
Solution 1 - Lye Solution:
To one pint of water in a quart jar (0.5 litre in a one litre jar), slowly add one-third of a cup (70 ml) of lye. Stir carefully. Cover the jar with a lid, label it, and set it aside. (This lye solution is strongly alkaline and becomes quite hot, so wear gloves when preparing it or the jar will be too hot to hold.) Solution 1 will keep for three or four days, after which time it loses strength.
Solution 2 - Hydros Solution:
To one pint of water in a quart jar (0.5 litre in a one litre jar) slowly add 6 tablespoons (80 ml) of hydros. Stir carefully until the chemical is dissolved. This mixture is quite foul-smelling, so cover the jar tightly and then label it. It would also be advisable to do it in a well ventilated area. Before you set it aside, you can wrap it in a plastic bag to diminish the odor. Hydros is the reducing agent. It reduces the indigo by removing the oxygen from the indigo bath.
Indigo Stock Solution:
0.5 of a cup (120 ml) of Solution 1 (lye).
0.5 of a cup (120 ml) of Solution 2 (hydros).
3-4 tablespoons (45 - 60 ml) of powdered non-synthetic indigo.
You will need the indigo stock solution (as prepared above) plus more of Solution 2, hydros.
Recipe:
Heat 4 gallons (18 litres) of water to 120oF or 48oC in the dyepot. Then add 4 tablespoons (60 ml) of hydros, Solution 2, to remove the oxygen present in the water. STIR THIS Gently, if at all, because you do not want to incorporate even more oxygen into the solution! It may be sufficient to merely tip the covered dyepot gently back and forth to distribute the hydros. Now let the water and hydros stand, covered for 10 to 15 minutes to allow it to settle. Next add 4 to 8 tablespoons (60 - 120 ml) of the indigo stock solution. (Using the smaller amount will yield light blues on 1 pound (453 g) of fiber, while the large amount will give medium to dark blue with the same amount of fiber. Cover the bath, and again allow it to sit undisturbed for 20 to 30 minutes to allow the chemicals and indigo to settle. During this time the temperature should be maintained at 120oF or 48oC. You can wrap an old blanket around the dyepot. The temperature may fall a few degrees, but this is all right as long as it does not exceed 120o or 48oC. The bath will now appear to be a yellowish green. This is normal.
It is most important to remember if you feel uncomfortable to carry out this recipe, seek a very experienced dyer who can walk you through this process safely until you have mastered it. THIS IS A MANDATORY STEP FOR NOVICE DYERS.
Dyeing with Indigo
Enter the wet fiber by easing it into the dyepot. Take care not to plunge it in, thereby introducing bubbles (i.e. oxygen). Once the fiber is in, replace the lid and put the dyepot on the heat. Always keep the temperature below 120oF or 48oC. This is a conservative figure: some dyers consider a temperature of 140oF or 60oC safe, but novice dyers should stick to the lower temperatures. Allow the first skein (ie. a length of thread or yarn or cloth, loosely coiled and knotted) to remain in the bath for 20 to 30 minutes. Take out the fiber and oxidize it.
Oxidation Process:
This is what turns the fiber blue, or actually, more blue. Hold the dripping skein OVER A BUCKET (so as not to introduce additional oxygen to the bath) and allow it to drip for several minutes. Within 30 to 60 seconds it will turn blue, a color much more definite than it was in the dyepot.
Turn the skein one way and then another so all of it is oxidized. If the color is satisfactory, hang the skein up to drip and label it (first dip etc.) It may be re-dipped later on or, if you want a dark blue, returned to the dyepot immediately. Some dyers claim stronger blues can be achieved if the indigo fibers are oxidised in sunlight, outdoors, for ten to twenty minutes between dips.
Control of Color
The color given by an indigo bath is governed by the amount of stock solution used, the time the fiber is in the bath, and the number of dips. As a dyer gains experience, the colors can be predicted with a fair degree of accuracy, based on previous records. Indigo blues are beautiful as they are, but extremely handsome when topped with strong yellows to produce greens, Experiment! No other dyestuff is quite so time-consuming and yet so rewarding.
Neutralizing
After each skein has been removed from its final dip, it must be neutralized, because it is strongly alkaline. To neutralize the skein the following steps should be invoked:
(i) Rinse the indigo-dyed fiber in lukewarm water to which one cup (240 ml) of vinegar has been added for each pound (453 g) of fiber.
(ii) Rinse next in cool water.
(iii) Rinse a third time in a lukewarm bath using a non-detergent soap.
(iv) Rinse a fourth time in clear, cool water and hang to dry.
Drying:
To avoid streaking indigo skeins, turn the fiber around often as it is drying. This prevents excess moisture from dripping onto one part of the skein. Drape over a plastic-covered rod or plastic clothesline. The dye might stain a painted wooden railing on a porch or fence.
Disposal of Indigo Bath
Since lye and hydros in the indigo bath are strongly alkaline, it will not harm the plumbing to pour it down the sink. After all, many people use lye to unclog drains. However, the indigo solution is messy; its purple slime clings to whatever it touches. Rural dyers with septic systems may wish to dispose of an indigo bath by digging a hole and pouring it into the ground in a spot where children and animals cannot get to. For city folk it is always best to have a conversation with your local council environmental officer.
Cleaning Equipment
All equipment used in indigo dyeing must be carefully cleaned, as even minute traces of the blue residue will spoil subsequent non-indigo baths. Throw stirrers away unless they are glass or plastic. Scrub all utensils with warm water and detergent soap. Then rinse them with a chlorine solution (i.e. a mild bleach solution) followed by a clear water rinse.
Bottoming and Topping with Indigo
Indigo-dyed fibers can be over-dyed with other dyestuff to obtain good greens and already dyed yellows can be made green with subsequent dips in the indigo bath. "Topping" usually refers to the process of covering a light shade, such as yellow, with a darker one, such as blue. "Bottoming" is the reverse: the dark shade is dyed first and the light one goes on top. It is a matter of personal preference which method you use to obtain greens (or any other colors) from indigo. The equality of the resulting color depends on the clarity of the yellow dye. Goldenrod yellows tend to give bluish-greens when topped with indigo; the colors are unique and extremely attractive. Using indigo dyes and other colored dyes will yield colors ranging from turquoise to a variety of navy and dark blues. The turquoise can be made using goldenrod yellow topped with indigo. Indigo dyers are passionate about creating new hues; some have topped soft dogwood rose-greys with indigo for purple heather effects.
Reference:
[1] K.L. Casselman, Craft of the Dyer, University of Toronto Press, Toronto (1980).
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