Dye

A dye is a colored substance that chemically bonds to a substrate to which it is being applied. This distinguishes dyes from pigments which have not chemically bind to the material they color. Dye is loosely applied in an aqueous solution, as living as may require a mordant to update the fastness of the dye on the fiber.

Both dyes in addition to pigments are colored, because they absorb only some wavelengths of visible light. Dyes are normally soluble in water whereas pigments are insoluble. Some dyes can be rendered insoluble with the addition of salt to pull in a lake pigment.

Types

Dyes are classified according to their solubility as well as chemical properties.

Acid dyes are water-soluble anionic dyes that are applied to fibers such as silk, wool, nylon and modified acrylic fibers using neutral to acid dye baths. Attachment to the fiber is attributed, at least partly, to salt formation between anionic groups in the dyes and cationic groups in the fiber. Acid dyes are not substantive to cellulosic fibers. nearly synthetic food colors fall in this category. Examples of acid dye are Alizarine Pure Blue B, Acid red 88, etc.

Basic dyes are water-soluble cationic dyes that are mainly applied to acrylic fibers, but find some usage for wool and silk. normally acetic acid is added to the dye bath to assist the uptake of the dye onto the fiber. Basic dyes are also used in the coloration of paper.

Direct or substantive dyeing is normally carried out in a neutral or slightly alkaline dye bath, at or almost boiling point, with the addition of either sodium chloride NaCl or sodium sulfate Na₂SO₄ or sodium carbonate Na₂CO₃. Direct dyes are used on cotton, paper, leather, wool, silk and nylon. They are also used as pH indicators and as biological stains.

Mordant dyes require a mordant, which improves the fastness of the dye against water, light and perspiration. The selection of mordant is very important as different mordants can modify thecolor significantly. Most natural dyes are mordant dyes and there is therefore a large literature base describing dyeing techniques. The most important mordant dyes are the synthetic mordant dyes, or chrome dyes, used for wool; these comprise some 30% of dyes used for wool, and are particularly useful for black and navy shades. The mordant potassium dichromate is applied as an after-treatment. it is important to note that many mordants, particularly those in the heavy metal category, can be hazardous to health and extreme care must be taken in using them.

Vat dyes are essentially insoluble in water and incapable of dyeing fibres directly. However, reduction in alkaline liquor produces the water-soluble alkali metal salt of the dye. This realize is often colorless, in which effect it is referenced to as a Leuco dye, and has an affinity for the textile fibre. Subsequent oxidation reforms the original insoluble dye. The color of denim is due to indigo, the original vat dye.

Cibacron F, and Drimarene K, are very easy to usage because the dye can be applied at room temperature. Reactive dyes are by far the best choice for dyeing cotton and other cellulose fibers at domestic or in the art studio.

Disperse dyes were originally developed for the dyeing of cellulose acetate, and are water-insoluble. The dyes are finely ground in the presence of a dispersing agent and sold as a paste, or spray-dried and sold as a powder. Their main use is to dye polyester, but they can also be used to dye nylon, cellulose triacetate, and acrylic fibers. In some cases, a dyeing temperature of 130 °C 266 °F is required, and a pressurized dyebath is used. The very excellent particle size helps a large surface area that aids dissolution to let uptake by the fiber. The dyeing rate can be significantly influenced by the choice of dispersing agent used during the grinding.

Azoic dyeing is a technique in which an insoluble components. With suitable adjustment of dyebath conditions the two components react to produce the asked insoluble azo dye. This technique of dyeing is unique, in that thecolor is controlled by the choice of the diazoic and coupling components. This method of dyeing cotton is declining in importance due to the toxic nature of the chemicals used.

Sulfur dyes are inexpensive dyes used to dye cotton with dark colors. Dyeing is effected by heating the fabric in a result of an organic compound, typically a nitrophenol derivative, and sulfide or polysulfide. The organic compound reacts with the sulfide address to form dark colors that adhere to the fabric. Sulfur Black 1, the largest selling dye by volume, does non have a alive defined chemical structure.

Some dyes commonly used in Staining: