Denim washing is an aesthetic finish that enhances the appeal and strength of the denim fabric. Dry denim, in contrast to washed denim, is a denim fabric that is not washed after being dyed during its production. Much of the appeal of dry denim lies in the fact that over time the fabric will fade in a way that attempts to artificially replicate denim. With dry denim, however, such discoloration is affected by the body of the person who wears jeans and the activities of their daily lives. This creates something that looks more natural, unique than pre-distressed denim. In denim washing, some basic chemicals are used, such as anti-back staining agent, detergent, soda ash, enzyme, stone, hydrogen peroxide, acetic acid, potassium permanganate, bleach, Meta, hypo, softener, etc.
List of Denim Washing Chemicals and Their Functions
- Anti-backstaining Agent
- Detergent or soaping agent
- Soda ash
- Hydrogen peroxide
- Bleaching agents
- Laundry enzymes
- Sodium metabisulfite (Meta)
- Sodium thiosulfate or hypo
- Acetic Acid
- Phosphoric acid
- Potassium permanganate
- Fixing agent
Above all denim washing chemicals are described below:
1. Anti back staining agent:
Anti back staining agent is one of the important denim washing chemicals that is used in washing for pocket cleaning and protect inside weft yarn bleeding. Cellulose is degraded during different types of washing and released indigo dye. For example, cellulose enzymes are temporarily bound to cellulose through an anchor. After this process, it is made available for a further hydrolysis reaction. To avoid this type of back staining, which will reduce the cost of clothing on the world market, some anti-back staining agents are used in wash baths. These agents are combined with other chemicals associated with bath washing. These agents are capable of prohibited actions, where removed dyes are re-deposited on clothing. Anti-back staining agents are mostly composed of three substances-
- Dispersing agents,
- Chelating agents and,
- Emulsifying agents.
- Anti back staining agent mainly used as a pocket clear or cleaning agent.
- Inside bleeding protector
- Sometimes it is used as a de-sizing agent.
2. Detergent or soaping agent:
Detergent is a cleaning agent that is used in the washing process for cleaning the garments or removing the size materials. It is a common among the denim washing chemicals. The soaping agent is designed not only to remove the unfixed dye but also to disperse the removed dye into the bath and to prevent it from re-attaching to the fiber. These detergents are usually found as powdered or concentrated solutions, and their solutions are often complex mixtures of various chemicals excluding surfactants. Detergents like soaps work because they are amphiphilic are partly hydrophilic and partly hydrophobic.
- Detergent mainly used as a cleaning agent
- It is also used in desizing process.
3. Soda ash:
Soda ash is a white, odorless, water-soluble salt that produces moderate alkaline solutions in water. It is used as washing soda and is the most common hydrate of sodium carbonate containing 10 molecules of water of crystallization. The soda ash is dissolved in water and crystallized to get the washing soda.
- Soda ash is mainly used in the washing process for cleaning garments.
- It is used in de-sizing process when needs a redder shade.
- It is used in the sulfur bleaching process for sulfur dyeing fabric.
4. Hydrogen peroxide:
Hydrogen peroxide is a very pale blue liquid, slightly more viscous than water. It is used as an oxidizer, bleaching agent, and antiseptic for medical. It is usually a dilute solution in water for consumer use and for high concentrations for industrial use. It is a reactive oxygen species and the simplest peroxide, a compound that has an oxygen-oxygen single bond. When exposed to light it decomposes slowly and rapidly in the presence of organic or reactive compounds. It is usually stored in a black bottle with a stabilizer in a weakly acidic solution to prevent light.
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- Hydrogen peroxide is mainly used in washing for mild bleaching agents.
- It is used in the sulfur bleaching process.
- It is used as a cleaning agent
- Sometimes it is used as a pp neutralizer with acid.
5. Bleaching agents:
Bleaching agents are solutions or powders that whiten or lighten a fabric by solubilizing color-producing substances or by altering their light-absorbing properties. It is used extensively in the washing industry for color fading or required shade achievement. In the denim washing factory sodium hypochlorite (NaOCl) bleach is mostly used.
- Bleach is used as a color fading agent
- It is also used for machine cleaning.
6. Laundry enzymes:
Laundry enzymes are the largest application in the denim washing industry for enzyme wash. It must be able to function normally in a wide array of conditions are water temperatures ranging from 0 to 60°C, alkaline and acidic environments, and the presence of surfactants or oxidizing agents. It can be fade color in denim or jeans cloth.
- Enzymes are removed hairiness from fabric or garments.
- It is used for color fading.
- It is used for desired effect
- It gives hi-low effect on garment
7. Sodium metabisulfite (Meta):
Sodium metabisulfite or Meta is a chemical compound that is used in bleach and potassium permanganate neutralizing agents.
- Meta work as a neutralizing agent.
- It is used when need blue shade
- It is used in bleach neutralize and pp neutralize
8. Sodium thiosulfate or hypo:
Sodium thiosulfate or hypo is an inorganic compound whose formula is Na2S2O3.xH2O which is available as white or colorless pentahydrate, Na2S2O3·5H2O. It is used to dechlorinate tap water with chlorine levels for use in aquariums, swimming pools, and spas, and water treatment plants, and treats permanent backwash water before it is released into the river. So, it is used as a neutralizing agent in denim washing projects for chlorine bleach.
- Hypo is used as a chlorine bleach neutralizing agent in the denim washing plant.
- It is used, when need redder shade.
9. Acetic acid:
Acetic acid is a colorless liquid and organic compound containing the chemical formula CH3COOH. It is the second simplest carboxylic acid. It is an important chemical reagent and industrial chemical that is primarily used to make cellulose acetate for photographic film, polyvinyl acetate for wood glue, and synthetic fibers and fabrics. The risk of acetic acid solutions depends on the concentration. Concentrated acetic acid can burn not only with difficulty at standard temperatures and pressures but also at high temperatures above 39°C.
- Acetic acid mainly used as a common neutralizer in denim industry.
- It works as a pH controller in enzyme and softener process
- It neutralizes the alkali in denim wash.
- It gives the shade redder.
10. Phosphoric acid:
Phosphoric acid is a weak acid with the chemical formula H3PO4. The pure compound is a colorless solid. It is commonly encountered in chemical laboratories as an 85% aqueous solution, which is a colorless, odorless, and non-volatile syrupy liquid. Although phosphoric acid does not meet the strict definition of a strong acid, 85% of the solution can cause severe skin irritation and eye damage.
- Phosphoric acid mainly used in wash factory as a pp activator.
- Sometimes it is used as an alkali neutralizer.
11. Potassium permanganate:
Potassium permanganate is an inorganic compound that contains the chemical formula KMnO4 and is composed of K+ and MnO4-. It is a purple-black crystal salt, which dissolves in water to give an intense pink or purple solution. It is widely used in the chemical industry and denim factories as a powerful oxidizing agent.
- It is mainly used in denim industries for specific portion oxidizing.
- Sometimes it is used as a pp bleach in denim bath.
Resin is a natural or synthetic polymer compound that is used in denim washing industry for giving stiffer or harder the garments or fabric. When special requirement from buyer then it is used.
- After resin treatment garments feel harder
- It gives the garment rigid look.
13. Fixing agent:
Denim garments colorfastness is very poor. So need good fixing agent for getting better crocking or rubbing fastness. Denim dyeing is used to remove weakly bound unfix dyes from the fiber substrate. Fixing agents may be induced after dyeing which can improve the durability of the previously formed co-valent bonds between the dye and the fiber molecule.
- Fixing agent improve the colorfastness.
- It removes the unfix dyes.
- It improve the crocking or rubbing fastness.
Softener is a finishing agent that enhances its handle when applied to textile materials and gives a pleasant touch. As a general rule, applied to softening agents are lubricating agents, which facilitate fiber sliding into the fabric structure, thus providing easy deformation and creasing of the fabric. Currently, the market for low gear softeners is often a mixture of fatty acids and silicone products of this type.
- Softener gives the garments soft in touch.
- It removes the stiffness of the garments.
- It gives the attractive looks of the garment
Author of this Article:
Chemist at Sajid Washing & Dyeing (Ha-meem Group)
Founder of Advanced Textile 86
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Founder & Editor of Textile Learner. He is a Textile Consultant, Blogger & Entrepreneur. He is working as a textile consultant in several local and international companies. He is also a contributor of Wikipedia.