Vat dye

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Vat dyes are a class of dyes that are classified as such because of the method by which they are applied. Vat dyeing is a process that refers to dyeing that takes place in a bucket or vat. The original vat dye is indigo, once obtained only from plants but now often produced synthetically. [1]

Contents

Materials suited for vat dyeing

Although almost all dyeing can be done in a vat, the term vat dye is used to describe a chemical class of dyes that are applied to cellulosic fibre (i.e., cotton) using a redox reaction as described below. Because of the use of caustic soda, and the very high pH of the dye bath in the dyeing process, wool cannot be dyed using vat dyestuffs. This is because wool is soluble in caustic soda solutions. Instead, it is possible to dye wool at room temperatures with indigo (vat blue 1) and other low substantive vat dyes using soda ash as the alkali source with very little strength loss. Vat red 10, vat violet 13 and vat orange 1 can be applied in this manner as well. [2]

Dyeing process

Vat dyes characteristically require a reducing agent to solubilize them. The most common reducing agent is sodium dithionite (Na2S2O4), which converts the dye to its "leuco" form that is soluble. Once attached to the fabric, the leuco dye is then oxidized to the insoluble state which is intensely colored. Chemical reactions such as oxidation, reduction, pH  control are often necessary; even the dissolution process necessitates measuring out appropriate quantities of caustic soda and sodium hydrosulphite in order to achieve reduction. The dye is soluble only in its reduced form. The fiber is immersed repeatedly in this oxygen-free dyebath, then exposed to the air, whereupon the water-soluble reduced form changes color as oxygen turns it to the water-insoluble form. For these reasons, vat dyes are less suitable than fiber-reactive dyes for amateur use.

Indigo is an example of this dye class: it changes from yellow, in the dyebath, to green and then blue as the air hits it.

Not all vat dyeing is done with vat dyes.

Properties

The vat dyes have high color fastness, which is uncommon in other dye classes. On the other hand, vat dyes tend to have poor rubbing fastness, but this can be mitigated with special treatments to the fabric. Indigo is subject to major crocking (i.e., rubbing the dye off onto other items) unless it is applied carefully. This means that dipping many times in a weaker dye-bath is more preferred than to dip once in a stronger dye-bath.

Light-oxidized vat dyes

Inkodye is a type of vat dye that uses light rather than oxygen to "fix" the dye, with a wide variety of possible effects. These dyes, which are chemically similar to vat dyes, are developed by light instead of being applied in an oxygen-free bath and being developed in the fabric by exposure to oxygen. Inkodyes are true dyes, not fabric paints. A dye itself attaches to the fabric; fabric paint includes a glue-like binder, which imparts a stiffer feeling to the fabric.

Chemical structures

For example, vat blue 2 and 3 are halogenated or methylated derivatives and so are several violets. Many other vat dyes are derivatives of anthroquinones. [3]

Related Research Articles

<span class="mw-page-title-main">Dye</span> Soluble chemical substance or natural material which can impart color to other materials

A dye is a colored substance that chemically bonds to the substrate to which it is being applied. This distinguishes dyes from pigments which do not chemically bind to the material they color. Dye is generally applied in an aqueous solution and may require a mordant to improve the fastness of the dye on the fiber.

<span class="mw-page-title-main">Indigo</span> Shade of blue

Indigo is a term used for a number of hues in the region of blue. The word comes from the ancient dye of the same name. The term "indigo" can refer to the color of the dye, various colors of fabric dyed with indigo dye, a spectral color, one of the seven colors of the rainbow, or a region on the color wheel, and can include various shades of blue, ultramarine, and green-blue. Since the web era, the term has also been used for various purple and violet hues identified as "indigo", based on use of the term "indigo" in HTML web page specifications.

<span class="mw-page-title-main">Indigo dye</span> Chemical compound, food additive and dye

Indigo dye is an organic compound with a distinctive blue color. Indigo is a natural dye extracted from the leaves of some plants of the Indigofera genus, in particular Indigofera tinctoria; dye-bearing Indigofera plants were commonly grown and used throughout the world, in Asia in particular, as an important crop, with the production of indigo dyestuff economically important due to the historical rarity of other blue dyestuffs.

<span class="mw-page-title-main">Mordant</span> Substance used for binding dyes to fabrics

A mordant or dye fixative is a substance used to set dyes on fabrics. It does this by forming a coordination complex with the dye, which then attaches to the fabric. It may be used for dyeing fabrics or for intensifying stains in cell or tissue preparations. Although mordants are still used, especially by small batch dyers, it has been largely displaced in industry by directs.

<span class="mw-page-title-main">Tie-dye</span> Technique of resist dyeing

Tie-dye is a term used to describe a number of resist dyeing techniques and the resulting dyed products of these processes. The process of tie-dye typically consists of folding, twisting, pleating, or crumpling fabric or a garment, before binding with string or rubber bands, followed by the application of dye or dyes. The manipulations of the fabric before the application of dye are called resists, as they partially or completely prevent ('resist') the applied dye from coloring the fabric. More sophisticated tie-dye may involve additional steps, including an initial application of dye before the resist, multiple sequential dyeing and resist steps, and the use of other types of resists and discharge.

Sulfur dyes are the most commonly used dyes manufactured for cotton in terms of volume. They are inexpensive, generally have good wash-fastness, and are easy to apply. Sulfur dyes are predominantly black, brown, and dark blue. Red sulfur dyes are unknown, although a pink or lighter scarlet color is available.

<span class="mw-page-title-main">Dyeing</span> Process of adding color to textile products

Dyeing is the application of dyes or pigments on textile materials such as fibers, yarns, and fabrics with the goal of achieving color with desired color fastness. Dyeing is normally done in a special solution containing dyes and particular chemical material. Dye molecules are fixed to the fiber by absorption, diffusion, or bonding with temperature and time being key controlling factors. The bond between the dye molecule and fiber may be strong or weak, depending on the dye used. Dyeing and printing are different applications; in printing, color is applied to a localized area with desired patterns. In dyeing, it is applied to the entire textile.

<span class="mw-page-title-main">Indanthrone blue</span> Organic dye made from 2-aminoanthraquinone

Indanthrone blue, also called indanthrene, is an organic compound with the formula (C14H6O2NH)2. It is a dark blue solid that is a common dye as well as a precursor to other dyes.

<span class="mw-page-title-main">Sun printing</span>

Sun printing may refer to various printing techniques which use sunlight as a developing or fixative agent.

<span class="mw-page-title-main">Thermochromism</span> Property of substances to change colour due to a change in temperature

Thermochromism is the property of substances to change color due to a change in temperature. A mood ring is an excellent example of this phenomenon, but thermochromism also has more practical uses, such as baby bottles which change to a different color when cool enough to drink, or kettles which change color when water is at or near boiling point. Thermochromism is one of several types of chromism.

<span class="mw-page-title-main">Acid dye</span> Dye applied to low pH textile

An acid dye is a dye that is typically applied to a textile at low pH. They are mainly used to dye wool, not cotton fabrics. Some acid dyes are used as food colorants, and some can also be used to stain organelles in the medical field.

<span class="mw-page-title-main">Leuco dye</span>

A leuco dye is a dye which can switch between two chemical forms, one of which is colorless. Reversible transformations can be caused by heat, light or pH, resulting in examples of thermochromism, photochromism and halochromism respectively. Irreversible transformations typically involve reduction or oxidation. The colorless form is sometimes referred to as the leuco form.

<span class="mw-page-title-main">Blue bottle experiment</span> Color-changing redox chemical reaction

The blue bottle experiment is a color-changing redox chemical reaction. An aqueous solution containing glucose, sodium hydroxide, methylene blue is prepared in a closed bottle containing some air. Upon standing, it spontaneously turns from blue to colorless due to reduction of methylene blue by the alkaline glucose solution. However, shaking the bottle oxidizes methylene blue back into its blue form. With further shaking, this color-change cycle can be repeated many times. This experiment is a classic chemistry demonstration that can be used in laboratory courses as a general chemistry experiment to study chemical kinetics and reaction mechanism. The reaction also works with other reducing agents besides glucose and other redox indicator dyes besides methylene blue.

<span class="mw-page-title-main">Natural dye</span> Dye extracted from plant or animal sources

Natural dyes are dyes or colorants derived from plants, invertebrates, or minerals. The majority of natural dyes are vegetable dyes from plant sources—roots, berries, bark, leaves, and wood—and other biological sources such as fungi.

<span class="mw-page-title-main">Glossary of dyeing terms</span>

Dyeing is the craft of imparting colors to textiles in loose fiber, yarn, cloth or garment form by treatment with a dye. Archaeologists have found evidence of textile dyeing with natural dyes dating back to the Neolithic period. In China, dyeing with plants, barks and insects has been traced back more than 5,000 years. Natural insect dyes such as Tyrian purple and kermes and plant-based dyes such as woad, indigo and madder were important elements of the economies of Asia and Europe until the discovery of man-made synthetic dyes in the mid-19th century. Synthetic dyes quickly superseded natural dyes for the large-scale commercial textile production enabled by the industrial revolution, but natural dyes remained in use by traditional cultures around the world.

<span class="mw-page-title-main">Paper chemicals</span> Chemicals used in paper manufacturing

Paper chemicals designate a group of chemicals that are used for paper manufacturing, or modify the properties of paper. These chemicals can be used to alter the paper in many ways, including changing its color and brightness, or by increasing its strength and resistance to water. The chemicals can be defined on basis of their usage in the process.

Wet Processing Engineering is one of the major streams in Textile Engineering or Textile manufacturing which refers to the engineering of textile chemical processes and associated applied science. The other three streams in textile engineering are yarn engineering, fabric engineering, and apparel engineering. The processes of this stream are involved or carried out in an aqueous stage. Hence, it is called a wet process which usually covers pre-treatment, dyeing, printing, and finishing.

<span class="mw-page-title-main">Lumi (company)</span>

Lumi is a Los Angeles–based company founded by Jesse Genet and Stephan Ango that offers packaging and supply chain management software. The company got its start developing Inkodye, a photo-reactive vat dye that develops its color through exposure to UV or sunlight.

<span class="mw-page-title-main">Synthetic colorant</span>


A colorant is any substance that changes the spectral transmittance or reflectance of a material. Synthetic colorants are those created in a laboratory or industrial setting. The production and improvement of colorants was a driver of the early synthetic chemical industry, in fact many of today's largest chemical producers started as dye-works in the late 19th or early 20th centuries, including Bayer AG(1863). Synthetics are extremely attractive for industrial and aesthetic purposes as they have they often achieve higher intensity and color fastness than comparable natural pigments and dyes used since ancient times. Market viable large scale production of dyes occurred nearly simultaneously in the early major producing countries Britain (1857), France (1858), Germany (1858), and Switzerland (1859), and expansion of associated chemical industries followed. The mid-nineteenth century through WWII saw an incredible expansion of the variety and scale of manufacture of synthetic colorants. Synthetic colorants quickly became ubiquitous in everyday life, from clothing to food. This stems from the invention of industrial research and development laboratories in the 1870s, and the new awareness of empirical chemical formulas as targets for synthesis by academic chemists. The dye industry became one of the first instances where directed scientific research lead to new products, and the first where this occurred regularly.

In textile processing, stripping is a color removal technique employed to partially or eliminate color from dyed textile materials. Textile dyeing industries often face challenges like uneven or flawed dyeing and the appearance of color patches on the fabric's surface during the dyeing process and subsequent textile material processing stages. Stripping is one of the reprocessing methods used to correct undesirable colors and flaws in dyed materials. The efficacy of this process relies on factors such as the dye type, fiber material, and the stripping agents utilized. Additionally, the procedure is recognized by alternative terms, namely back stripping or destructive stripping.

References

  1. Booth, Gerald (2000). "Dyes, General Survey". Ullmann's Encyclopedia of Industrial Chemistry. Wiley-VCH. doi:10.1002/14356007.a09_073. ISBN   3527306730.
  2. The Chemistry of Vat Dyes by Dianne Epps
  3. Bien, H.-S.; Stawitz, J.; Wunderlich, K. "Anthraquinone Dyes and Intermediates". Ullmann's Encyclopedia of Industrial Chemistry . Weinheim: Wiley-VCH. doi:10.1002/14356007.a02_355. ISBN   978-3527306732.{{cite encyclopedia}}: CS1 maint: multiple names: authors list (link)

Imagery on Fabric by Jean Ray Laury