Vat dye
Encyclopedia
Vat dyes are an ancient class of dye
s, based on the natural dye
, indigo
, which is now produced synthetically.
, wool
, and other fiber
s can be all dyed with vat dyes. Note that not all vat dyeing is done with vat dyes.
Most vat dyes are less suitable than fiber reactive dyes for the home dyers, as they are difficult to work with; they require a reducing agent to solubilize them. The dye is soluble only in its reduced (oxygen-free) 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. 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.
Indigo is subject to major crocking (rubbing the dye off onto other items) unless it is applied carefully. This means use a weaker dyebath, and dipping many times, rather than a single strong dipping.
There are several methods available for the application of vat dyes to yarn and fabric.
The Vat dyes are having all around fastness properties which cannot be possible in any class of dyes .the only problem in this class is slightly poor rubbing fastness.which can be increased by special after treatment.
Dye
A dye is a colored substance that has an affinity to the substrate to which it is being applied. The dye is generally applied in an aqueous solution, and requires a mordant to improve the fastness of the dye on the fiber....
s, based on the natural dye
Natural dye
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 organic sources such as fungi and lichens....
, indigo
Indigo
Indigo is a color named after the purple dye derived from the plant Indigofera tinctoria and related species. The color is placed on the electromagnetic spectrum between about 420 and 450 nm in wavelength, placing it between blue and violet...
, which is now produced synthetically.
Overview
The process "vat dyeing" refers to dyeing in a bucket or vat. It can be performed whenever a liquid, even shade over the entire garment is desired. Almost any dye can be used, including fiber reactive dyes, direct dyes, and acid dyes. One alternative to vat dyeing is direct dye application, such as the process used for tie dyeing. "Vat dyes" are a special class of dyes that work with a special chemistry. CottonCotton
Cotton is a soft, fluffy staple fiber that grows in a boll, or protective capsule, around the seeds of cotton plants of the genus Gossypium. The fiber is almost pure cellulose. The botanical purpose of cotton fiber is to aid in seed dispersal....
, wool
Wool
Wool is the textile fiber obtained from sheep and certain other animals, including cashmere from goats, mohair from goats, qiviut from muskoxen, vicuña, alpaca, camel from animals in the camel family, and angora from rabbits....
, and other fiber
Fiber
Fiber is a class of materials that are continuous filaments or are in discrete elongated pieces, similar to lengths of thread.They are very important in the biology of both plants and animals, for holding tissues together....
s can be all dyed with vat dyes. Note that not all vat dyeing is done with vat dyes.
Most vat dyes are less suitable than fiber reactive dyes for the home dyers, as they are difficult to work with; they require a reducing agent to solubilize them. The dye is soluble only in its reduced (oxygen-free) 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. 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.
Light-oxidized Vat Dyes
Inkodye is a type of vat dye which 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. The process is more difficult than the process of tie-dyeing with fiber reactive dyes.Using vat dyes
PRO Chemical & Dye, which sells some vat dyes, provides instructions online for Immersion Dyeing using PRO Vat Dyes. The process requires the use of lye (sodium hydroxide), which must be used with due care, including the use of safety goggles.Indigo is subject to major crocking (rubbing the dye off onto other items) unless it is applied carefully. This means use a weaker dyebath, and dipping many times, rather than a single strong dipping.
Application of vat Dyes
Application of vat dyestuff is not so easy like direct or reactive dyes. The application involves a lot of chemistry - such as oxidation, reduction, pH control and so on. Even the dissolution of the dyestuff involves a great technique of reduction using adequate quantities of caustic soda and sodium hydrosulphite.There are several methods available for the application of vat dyes to yarn and fabric.
The Vat dyes are having all around fastness properties which cannot be possible in any class of dyes .the only problem in this class is slightly poor rubbing fastness.which can be increased by special after treatment.