Fabric dyeing differently Dyeing is is process of importing color to a textile material in loose fibre, yarn, cloth or garment form by treatment with a dye.
DYE can generally be described as a colored substance that has an affinity to substrate to which it is being applied. Dye is generally applied in an aqueous solution, & may require a mordant to improve fastness of the dye on the fiber. Direct application
The term direct dye application stems from some dyestuff having to be either fermented as in case of some natural dye or chemically reduced as in case of synthetic Vat and Sulphur dyes before being applied. This renders dye soluble so that it can be absorbed by fibre, insoluble dye has very little substantively to fibre. Direct dyes, a class of dyes largely for dying cotton, are water soluble & can be applied directly to fibre from an aqueous solution. Most other classes of synthetic dye, other than vat and sulpur dyes, are also applied in this way. The term may also be applied to dyeing without use of mordant to fix dye once it is applied. Mordant were often required to alter hue & intensity of natural dyes & improve their color fastness. Chromium salts were until recently extensively used in dying wool with synthetic mordant dyes. These were used for economical high color fastness dark shades such as Black & Navy. Environmental concern have now restricted their use & they have been replaced with reactive & metal complex dyes which need no mordant Yarn dyeing
There are many forms of yarn dyeing. Common forms are -at package form & at honks form. Cotton yarns are mostly dyed at package form, and acrylic or wool yarn are dyed at hank form The common dyeing process of cotton yarn with reactive dyes at package form is given below in short- firstly raw yarn is winded on spring tube to achieve package suitable for dye penetration. then, these softened packages are loaded on a dyeing carrier's spindle one on other. Then, packages are pressed up to a desired height to achieve suitable density of pkg. then, carrier is loaded on dyeing machine and yarn is dyed. After dyeing, packages are unloaded from carrier in to a trolly. Then, all packages are hydro extracted to remove maximum amount of water. then, all packages are dried to achieve final dyed package. at last dyed yarn packages are packed and delivered Both dyes & pigments appear to be colored because they absorb some wavelengths of light preferentially. In contrast with a dye, a pigment generally is insoluble, & has no affinity for substrate. Some dyes can be precipitated with an inert salt to produce a lake pigment. Archaeological evidence shows that, particularly in India & the Middle East, dyeing has been carried out for over 5000 years. The dyes were obtained from animal, vegetable or mineral origin, with no or very little processing. By far the greatest source of dyes has been from plant kingdom, notably roots, berries, bark, leaves and wood, but only a few have ever been used on a commercial scale. Color is the most important attribute to consumers . The colors in fabrics are infinite. They can be solids, multi-colored stripes, or other pattern effects such as floral and geometries. Dyeing of the material
can be done at any stage of making the fiber, yarn, or fabric. The desired effect to be achieved will usually dictate the dyeing method. For example, a multi-colored floral pattern requires individual yarns to be pre-colored to as many different shades as there are in the desired pattern. The various colored yarns are then constructed into the floral pattern fabric. By contrast a
solid color can be achieved by constructing fabric first and then dyeing fabric. Another way to achieve a solid color or multi-color effect would be to use pre-dyed fiber, produce the colored yarn, and then construct the fabric. This assures consistently uniform color. Printing is localized coloration that also achieves multi-colored effects. Finishing We provide a wide range of finishing options, from scouring and prepare-for-print to a variety of soft to medium finishes to meet our customers' requirements. In addition, we also provide specialty finishes including soil resistant finishes, anti-microbial and water-repellent finishes. Finishing follows coloration. This treatment can be mechanical, chemical, or both. The mechanical treatment is done at the textile mill or dye house. It can be one of various surface treatments. Brushing and sanding of fabrics, for example, can provide extra sheen and luster.
Dye laser A dye laser is a laser which uses an organic dye as lasing medium, usually as a liquid solution. Compared to gases and most solid state lasing media, a dye can usually be used for a much wider range of wavelengths. Wide bandwidth makes them particularly suitable for tunable lasers & pulsed lasers. Moreover, dye can be replaced by another type in order to generate different wavelengths with same laser, although this usually requires replacing other optical components in laser as well. Long-wavelength absorption band of laser dyes is attributed to transition from electronic ground state S0 to the first excited singlet state S 1. Transition moment for this process is typically very large, thus giving rise to an absorption band with oscillator strength on order of unity. Reverse process S 1->S0 is responsible for spontaneous emission known as fluorescence & for stimulated emission in dye lasers. Dye lasers are also used dermatologically, to make skin tone more
Close-up of a table-top dye laser based on Rhodamine 6G, emitting at 580nm (yellow-orange). Emitted laser beam is visible as faint yellow lines. Orange dye solution enters laser from left, & is
pumped by a 514nm (blue-green) beam from an argon laser. Dye jet is in center of image, behind yellow window. Organic Dyes
The first human-made (synthetic) organic dye, mauveine, was discovered by William Henry Perkin in 1856. Many thousands of synthetic dyes have since been prepared Synthetic dyes quickly replaced traditional natural dyes. They cost less, they offered a vast range of new colors, & they imparted better properties upon dyed materials. Dyes are now classified according to how they are used in dyeing process. Acid dyes Acid dyes are water-soluble anionic dyes that are applied to fibers such as silk, wool, nylon & modified acrylic fibers using neutral to acid dyebaths. Attachment to fiber is attributed, at least partly, to salt formation between anionic groups in dyes & cationic groups in fiber. Acid dyes are not substantive to cellulosic fibers. Basic Dyes Basic dyes are water-soluble cationic dyes that are mainly applied to acrylic fibers, but find some use for wool & silk. Usually acetic acid is added to dyebath to help uptake of dye onto fiber. Basic dyes are also used in the coloration of paper. Substantive Dyeing Direct or Substantive Dyeing is normally carried out in a neutral or slightly alkaline dyebath, at or near boiling point, with addition of either sodium chloride (NaCl) or sodium sulfate (Na 2SO4). Direct dyes are used on cotton, paper, leather, wool, silk & nylon. They are also used as pH indicators & as biological stains. (Substantive Dyeing is a dye used in a process in which dye molecules are attracted by physical forces at molecular level to textile. amount of this attraction is known as "substantively": higher the substantively the greater the attraction of the dye for the fiber). Mordant Dyes Mordant dyes require a mordant, which improves fastness of dye against water, light & perspiration. Choice of mordant is very important as different mordant can change final color significantly. Most natural dyes are mordant dyes & there is therefore a large literature base describing dyeing techniques. The most important mordant dyes are synthetic mordant dyes, or chrome dyes, used for wool; these comprise some 30% of dyes used for wool, & are especially useful for black & navy shades. The mordant, potassium dichromate, is applied as an after-treatment. It is important to note that many mordant, particularly those in hard metal category, can be hazardous to health & extreme care must be taken in using them.
(A mordant is a substance used to set dyes on fabrics by forming an insoluble compound with dye.) Cellulose is an organic compound with formula (C6H10O5)n.
Cellulose in 3D Reactive dyes Reactive dyes utilize a chromophore containing a substituent that is capable of directly reacting with fibre substrate. covalent bonds that attach reactive dye to natural fibers make it among the most permanent of dyes. "Cold" reactive dyes, such as Procion MX, Cibacron F, and Drimarene K, are very easy to use because dye can be applied at room temperature. Reactive dyes are by far the best choice for dyeing cotton and other cellulose fibers at home or in the art studio.
In a reactive dye a chromophore contains a substituent that is activated & allowed to directly react to the surface of the substrate. A chromophore is part (or moiety) of a molecule responsible for its color. Sulfur dyes Sulfur dyes are two part "developed" dyes used to dye cotton with dark colors. initial bath imparts a yellow or pale chartreuse color. This is oxidized in place to produce dark black we are familiar with in socks and the indigo blue of the common blue jeans.
Sulfur dyes are the biggest volume dyes manufactured for cotton. Redox (shorthand for reduction/oxidation reaction) describes all chemical reactions in which atoms have their oxidation number (oxidation state) changed. This can be either a simple redox process such as oxidation of carbon to yield carbon dioxide, or reduction of carbon by hydrogen to yield methane (CH4), or it can be a complex process such as the oxidation of sugar in the human body through a series of very complex electron transfer processes.The term redox comes from the two concepts of reduction and oxidation. It can be explained in simple terms:\\
Oxidation describes the loss of electrons by a molecule, atom or ion ,// Reduction describes the gain of electrons by a molecule, atom or ion .Top of Page However, these descriptions (though sufficient for many purposes) are not truly correct. Oxidation and reduction properly refer to a change in oxidation number —actual transfer of electrons may never occur. Thus, oxidation is better defined as an increase in oxidation number , and reduction as a decrease in oxidation number . In practice, transfer of electrons will always cause a change in oxidation number, but there are many reactions which are classed as "redox" even though no electron transfer occurs (such as those involving covalent bonds).Non-redox reactions, which do not involve changes in formal charge, are known as metathesis reactions.
Tie-dye is typically brightly colored, patterned textile or clothing which is made from ordinary cloth, usually cotton, through a resist dyeing process known as tie-dyeing. This is modern version of a traditional dyeing method. Resist dyeing , resist-dyeing and variants is a term for a number of traditional methods of dyeing textiles with patterns. Methods are used to "resist" or prevent dye from reaching all the cloth, thereby creating a pattern and ground. The most common forms use wax, some type of paste, or a mechanical resist that manipulates the cloth such as tying or stitching. Another form of resist involves using a chemical agent in a specific type of dye that will repel another type of dye printed over top.
