Dyeing can be applied at various stages within the
textile manufacturing process; for example, fibers may be dyed before being spun into yarns, and yarns may be dyed before being woven into fabrics. Fabrics and sometimes finished garments themselves may also be dyed. and 'mass coloration' or 'mass colored'. It has limited color options. •
Yarn dyeing: In yarn dyeing, the yarns are dyed first before the fabric manufacturing stage. The yarn dyeing happens in hanks or in package dyeing. Package dyeing is a method where yarns are wound on perforated cones placed in a dye vessel. The dye solution is then alternatively pushed inside out and vice versa. Examples are many stripes, patterned (checks) and jacquard designed fabrics. •
Piece dyeing: In piece dyeing, the dyeing takes place after producing fabrics with undyed yarns. Most of the solid dyed fabrics are dyed with the piece dyeing method, and the materials are also called piece dyed.
Terms for different dyed materials There are various terms used in the manufacturing and marketing industries depending on the method used to dye the substrate. For example, "stock dyed" refers to dyeing the fibers before making the yarn, "yarn dyed" refers to dyeing the yarns before producing fabrics, and "piece dyed" or "fabric dyed" refers to dyeing the yarns after they are converted into fabric. The fastness of fiber- and yarn-dyed materials is superior to that of fabrics.
Objective The primary objective of the dyeing process is to achieve uniform color application in accordance with a predetermined color matching standard or reference on the
substrate, which may be a fiber, yarn, or fabric, while meeting specified
colour fastness requirements. Tie-dye and printing are the methods where the color is applied in a localized manner.
Application vessel
Exhaust method In the exhaust method, the dye is transported to the substrate by the dye liquor's motion. The dye is adsorbed onto the fibre surface and ideally diffuses into the whole of the fibre. Water consumption in exhaust application is higher than the continuous dyeing method. Types of continuous dyeing are as follows • Pad-steam
Waterless dyeing method Waterless dyeing, also known as dry dyeing, is the newly developed and more sustainable dyeing method in which the dyes are applied to the substrate with the help of
carbon dioxide or solutions that need less or no water compared to their counterparts.
Selection of dyes The selection of the appropriate
dyes is most important because any given dye does not apply to every type of
fiber. Dyes are classified according to many parameters, such as chemical structure, affinity, application method, desired
colour fastness i.e. resistance to washing, rubbing, and light.
Indigo dyes have a poor wash and rubbing fastness on denim (cotton), so they are used to produce washed-down effects on fabrics. In contrast,
vat or
reactive dyes are applied to cotton to achieve excellent washing fastness. The next important criterion for selecting dyes is the assessment of hazards to human health and the
environment. There are many dyes especially
disperse dyes that may cause allergic reactions to some individuals, and the negative impact on the environment. There are national and international standards and
regulations which need to comply.
Direct application , a type of
vat dye The term "direct dye application" stems from some dyestuff having to be either fermented as in the case of some natural dye or chemically
reduced as in the case of synthetic vat and sulfur dyes before being applied. This renders the dye soluble so that it can be absorbed by the fiber since the insoluble dye has very little substantivity to the fiber. Direct dyes, a class of dyes largely for dyeing cotton, are water-soluble and can be applied directly to the fiber from an aqueous solution. Most other classes of synthetic dye, other than vat and surface dyes, are also applied in this way. The term may also be applied to dyeing without the use of
mordants to fix the dye once it is applied. Mordants were often required to alter the hue and intensity of natural dyes and improve
color fastness.
Chromium salts were until recently extensively used in dyeing wool with synthetic mordant dyes. These were used for economical high color fastness dark shades such as
black and
navy. Environmental concerns have now restricted their use, and they have been replaced with reactive and metal complex dyes that do not require mordant.
Yarn dyeing ) There are many forms of
yarn dyeing. Common forms are the package form and the hanks form. Cotton yarns are mostly dyed at package form, and acrylic or wool yarn are dyed at hank form. In the continuous filament industry, polyester or polyamide yarns are always dyed at package form, while viscose rayon yarns are partly dyed at hank form because of technology. The common dyeing process of cotton yarn with reactive dyes at package form is as follows: • The raw yarn is wound on a spring tube to achieve a package suitable for dye penetration. • These softened packages are loaded on a dyeing carrier's spindle one on another. • The packages are pressed up to a desired height to achieve suitable density of packing. • The carrier is loaded on the dyeing machine and the yarn is dyed. • After dyeing, the packages are unloaded from the carrier into a trolley. • Now the trolley is taken to hydro extractor where water is removed. • The packages are hydro extracted to remove the maximum amount of water leaving the desired color into raw yarn. • The packages are then dried to achieve the final dyed package. After this process, the dyed yarn packages are packed and delivered.
Space dyeing Space dyeing is a technique of localized color application that produces a unique multicolored effect. == Related terms ==