Editing Dye (section)

==Types==
[[File:RITdye.JPG|thumb|RIT brand dye from mid-20th century Mexico, part of the permanent collection of the [[Museo del Objeto del Objeto]]]]
[[File:Hårfärgning - 2007.jpg|thumb|A [[woman]] dyeing her [[hair]]]]
Dyes are classified according to their solubility and chemical properties.<ref name="Ullmann's Encyclopedia of Industrial Chemistry"/>

'''[[Acid dye]]s''' are [[water]]-[[soluble]] [[anionic]] dyes that are applied to [[fiber]]s such as [[silk]], [[wool]], [[nylon]] and modified [[acrylic fiber]]s 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 [[Cellulose|cellulosic]] fibers. Most 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 fiber]]s, but find some use for wool and silk. Usually [[acetic acid]] is added to the dye bath to help the uptake of the dye onto the fiber. Basic dyes are also used in the coloration of [[paper]].

'''Direct''' or '''[[substantive dye]]ing''' is normally carried out in a neutral or slightly [[alkaline]] dye bath, at or near [[boiling point]], with the addition of either [[sodium chloride]] (NaCl) or [[sodium sulfate]] (Na<sub>2</sub>SO<sub>4</sub>) or [[sodium carbonate]] (Na<sub>2</sub>CO<sub>3</sub>). Direct dyes are used on [[cotton]], paper, [[leather]], wool, silk and [[nylon]]. They are also used as [[pH indicator]]s and as [[staining (biology)|biological stains]].

[[organic dye laser|Laser dyes]] are used in the production of some lasers, optical media ([[CD-R#ORGANIC DYE|CD-R]]), and [[camera sensors]] ([[color filter array]]).<ref>{{cite book|url=https://books.google.com/books?id=_F4hAwAAQBAJ&q=organic+dye+laser&pg=PA539|title=Laser Fundamentals|first=William T.|last=Silfvast|date=21 July 2008|publisher=Cambridge University Press|access-date=8 November 2017|via=Google Books|isbn=9781139855570}}</ref>

'''[[Mordant dye]]s''' require a [[mordant]], which improves the fastness of the dye against water, [[light]] and [[perspiration]]. The choice of mordant is very important as different mordants can change the final color 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 especially 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 dye]]s''' 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 form is often colorless, in which case it is referred 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 dye|indigo]], the original vat dye.

'''[[Reactive dyes]]''' utilize a [[chromophore]] attached to a [[substituent]] that is capable of directly [[chemical reaction|reacting]] with the fiber substrate. The [[covalent]] bonds that attach reactive dye to natural fibers make them among the most permanent of dyes. "Cold" reactive dyes, such as [[Procion MX]], [[Cibacron F]], and [[Drimarene K]], are very easy to use 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 home or in the art studio.

'''[[Disperse dye]]s''' 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 {{convert|130|C|F}} is required, and a pressurized dyebath is used. The very fine particle size gives a large surface area that aids dissolution to allow 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 [[Azo dye]] is produced directly onto or within the fiber. This is achieved by treating a fiber with both diazoic and coupling [[wikt:component|components]]. With suitable adjustment of dyebath conditions the two components react to produce the required insoluble azo dye. This technique of dyeing is unique, in that the final color 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 dye]]s''' are inexpensive dyes used to dye cotton with dark colors. Dyeing is effected by heating the fabric in a solution of an organic compound, typically a nitrophenol derivative, and sulfide or [[polysulfide]]. The organic compound reacts with the sulfide source to form dark colors that adhere to the fabric. Sulfur Black 1, the largest selling dye by volume, does not have a well defined chemical structure.

'''Some dyes commonly used in Staining:''' 
{| class="wikitable"
|+
!Basic Dyes
!Acidic Dyes
|-
|[[Safranin]]
|[[Eosin]]
|-
|[[Fuchsine|Basic fuchsin]]
|[[Acid fuchsin]] 
|-
|[[Crystal violet]]
|[[Congo red]]
|-
|[[Methylene blue]]
|
|}
{{clear}}