# Textile bleaching

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{{Short description|Textile wet process that improves whiteness by removing natural color}}

thumb|right|Early method of bleaching cotton and linen goods on lawns
thumb|right| A bleach worker

The '''textile bleaching''' (or '''bleaching of textiles''') is [one of the steps](/source/Wet_process_engineering) in the [textile manufacturing](/source/textile_manufacturing) [process](/source/Finishing_(textiles)). The objective of bleaching is to remove the natural color for the following steps such as [dyeing](/source/dyeing) or [printing](/source/textile_printing) or to achieve full [white](/source/white).<ref>{{Cite book|last=Hummel|first=J. J. (John James)|url=https://archive.org/details/dyeingtextilefa01hummgoog|title=The dyeing of textile fabrics|date=1898|publisher=London [etc.] New York, Cassell and company, limited|others=Harvard University|pages=86}}</ref> All raw [textile](/source/textile) materials, when they are in natural form, are known as '[greige' material](/source/Greige_goods). They have their natural color, odor and impurities that are not suited to clothing materials. Not only the natural impurities will remain in the greige material, but also the add-ons that were made during its cultivation, growth and manufacture in the form of [pesticide](/source/pesticide)s, [fungicide](/source/fungicide)s, [worm killers](/source/Anthelmintic), [sizes](/source/Sizing), [lubricant](/source/lubricant)s, etc. The removal of these natural coloring matters and add-ons during the previous state of manufacturing is called scouring and bleaching.<ref name=":4">{{Cite book|last=Hall|first=A. J. (Archibald John)|url=https://archive.org/details/standardhandbook0000hall|title=The standard handbook of textiles|date=1969|location=New York |publisher= Chemical Pub. Co}}</ref>{{Rp|193}}<ref name=":7">{{Cite book|last=Clark|first=M.|url=https://books.google.com/books?id=9iFtAgAAQBAJ&q=Types+of+impurities+in+textile+fibers&pg=PA65|title=Handbook of Textile and Industrial Dyeing: Principles, Processes and Types of Dyes|date=2011-10-25|publisher=Elsevier|isbn=978-0-85709-397-4|pages=65, 66|language=en}}</ref><ref>{{Cite book|url=https://books.google.com/books?id=nxNbAAAAYAAJ&q=Any+foreign+material+other+than+fibres+is+classified+as+impurities.|title=The Cotton Year Book and Diary|date=1919|publisher=Marsden and Company, Limited|pages=470|language=en}}</ref>

A '''continuous bleaching''' range is a set of machines to carry out bleaching action. It consists of several compartments in which fabric moves from one side to another with the help of guide rollers and is treated with chemicals, heated, rinsed, and squeezed. Continuous bleaching is possible for the fabrics in open-width or rope form.<ref>{{Cite book |url=https://books.google.com/books?id=doLc_aM9lgwC&dq=continuous+bleaching&pg=PA668 |title=Code of Federal Regulations: Containing a Codification of Documents of General Applicability and Future Effect as of December 31, 1948, with Ancillaries and Index |date=1992 |publisher=Division of the Federal Register, the National Archives |pages=668 |language=en}}</ref><ref>{{Cite book |url=https://books.google.com/books?id=sWJGAQAAIAAJ&dq=continuous+bleaching&pg=RA12-PA147 |title=BLS Report |date=1953 |publisher=U.S. Department of Labor, Bureau of Labor Statistics |pages=147 |language=en}}</ref>

== History ==
Bleaching can be dated back to at least 1000&nbsp;BC from an Egyptian list found in the tomb of Rekh-mi-re at Thebes, which mentioned both bleached and unbleached linen.<ref name=":02">{{Cite book |last1=Nicholson |first1=Paul T. |url=https://books.google.com/books?id=Vj7A9jJrZP0C&pg=PA280 |title=Ancient Egyptian Materials and Technology |last2=Shaw |first2=Ian |date=2000-03-23 |publisher=Cambridge University Press |others=citing N Davies "The Tomb of Rekh-mi-re at Thebes" 1943, p.47 |isbn=978-0-521-45257-1 |pages=280 |language=en}}</ref> Mulrooney dates it back as far as 5000&nbsp;BC,<ref name=":1">{{Cite web |last1=Bach |first1=Julie |last2=Varatharajan |first2=Jenenee |title=Bleach (Sodium Hypochlorite): History |url=http://whatisbleach.weebly.com/history.html |archive-url=https://web.archive.org/web/20230311014220/https://whatisbleach.weebly.com/history.html |archive-date=11 March 2023 |access-date=2023-04-29 |website=whatisbleach.weebly.com}}</ref> while Walton claims it was introduced to Egypt from Asia.<ref name=":22">{{Cite book |last=Walton |first=Perry |url=http://archive.org/details/storyoftextiles00waltrich |title=The story of textiles |date=1912 |publisher=Boston, Mass., J. S. Lawrence |others=University of California Libraries |pages=111–115}}</ref> It’s plausible that it was discovered independently by different cultures. It’s generally assumed to have developed after noticing that garments are naturally bleached by sunlight and washing.<ref name=":02" /><ref name=":1" /> [Wood ash](/source/Wood_ash) ([potash](/source/potash), or impure [potassium hydroxide](/source/potassium_hydroxide)) was an early form of [soap](/source/soap), known to have been used in bleaching since at least 1&nbsp;AD.<ref name=":22" /><ref name=":32">{{Cite book |url=https://books.google.com/books?id=siQH2lVmxjoC&pg=PA410 |title=Crops in peace and war - The yearbook of agriculture 1950 - 1951 |date=1950 |publisher=U.S. Government Printing Office |pages=410 |language=en}}</ref> This process of washing cloth in a solution of ashes ([lye](/source/lye)) and left in the sun, known as [Grassing](/source/Grassing_(textiles)), is one of the oldest methods of [bleach](/source/bleach)ing [textile](/source/textile) goods. To bleach [linen](/source/linen) and [cotton](/source/cotton)-based fabrics, the Grassing method has been used. Linen has long been bleached in Europe with Grassing method.<ref name=":03">{{Cite book|last=Nystrom|first=Paul Henry|url=https://books.google.com/books?id=MH81AAAAMAAJ&q=Grassing.%E2%80%94The+oldest+bleaching|title=Textiles|date=1916|publisher=D. Appleton|pages=266|language=en|quote=''Grassing . — The oldest bleaching method is that of "grassing", still used to a certain extent in Europe for bleaching linens . The linen fabrics are laid on the grass or ground for weeks . The oxygen of the air and that given off by green plants''}}</ref> The linens were laid out on the grass for over seven days after boiling with the <nowiki>''lyes of ashes and rinsing''</nowiki>.<ref name=":23">{{Cite book|last=Sansone|first=Antonio|url=https://books.google.com/books?id=mmBDAQAAIAAJ&q=Grassing+bleaching&pg=PA109|title=Dyeing: Comprising the Dyeing and Bleaching of Wool, Silk, Cotton, Flax, Hemp, China Grass &c|date=1888|publisher=A. Heywood & son|pages=109|language=en}}</ref> [Bleachfield](/source/Bleachfield) was an open area to spread cloth, it was a field near watercourse used by a bleachery. Bleachfields were common in and around the [mill town](/source/mill_town)s [during the British Industrial Revolution](/source/Textile_manufacture_during_the_British_Industrial_Revolution)<ref name=":12">{{Cite book|last=Aspin|first=C. (Christopher)|url=https://archive.org/details/cottonindustry0000aspi|title=The cotton industry|date=1981|location=Aylesbury  |publisher= Shire Publications Ltd|isbn=978-0-85263-545-2|pages=24}}</ref>

The Dutch were bleaching by about the 12th century and are credited with soaking the bleached cloth in a bath of soured milk for 5–8 days.<ref name=":1" /><ref name=":32" /><ref name=":42">{{Cite book |url=https://books.google.com/books?id=fmBJAAAAYAAJ&pg=PA704 |title=The Encyclopaedia Britannica: A Dictionary of Arts, Sciences, and General Literature: Bleaching |date=1894 |publisher=Maxwell Sommerville |pages=704 |language=en}}</ref> This softened and neutralised the harsh effects of the caustic lye.<ref name=":1" /> By the 17th century the Dutch were renowned for their bleaching skills and much of their trade was for customers abroad.<ref>{{Cite book |last=Davids |first=Karel |url=https://books.google.com/books?id=bu95DwAAQBAJ&pg=PA134 |title=The Rise and Decline of Dutch Technological Leadership: Technology, Economy and Culture in the Netherlands, 1350-1800 |date=2008-08-31 |publisher=BRILL |isbn=978-90-474-4332-2 |volume=1 |pages=134 |language=en}}</ref><ref name=":42" /> Around 1756 an alternative to soured milk was proposed by the Scottish doctor, [Francis Home](/source/Francis_Home) using a weak solution of sulphuric acid.<ref>{{Cite journal |last=Page |first=Frederick G |date=2002 |title=Francis Home and Joseph Black: the Chemistry and Testing of Alkaline Salts in the Early Bleaching and Alkali Trade |url=https://docslib.org/doc/11501435/francis-home-and-joseph-black-the-chemistry-and-testing-of-alkaline-salts-in-the-early-bleaching-and-alkali-trade |journal=Bulletin for the History of Chemistry |volume=27 |issue=2 |pages=107–113 |via=docslib.org}}</ref> This was made commercially viable by [John Roebuck's](/source/John_Roebuck) manufacture of [sulphuric acid](/source/Sulfuric_acid)  and reduced the soaking time to 12–24 hours.<ref name=":42" /> A final rinse and drying finished the bleaching process.

The English East India Company imported bleached, painted and printed [calico](/source/calico) from India during the 17th century.<ref>{{Cite book |last=Chaudhuri |first=K. N. |url=https://books.google.com/books?id=Dyn3oh06ue8C&pg=PA199 |title=The English East India Company: The Study of an Early Joint-stock Company 1600-1640 |date=1999 |publisher=Taylor & Francis |isbn=978-0-415-19076-3 |pages=199 |language=en}}</ref> This disrupted the English silk and wool trades<ref>{{Cite web |title=House of Commons Journal Volume 11: 19 February 1696 {{!}} British History Online |url=https://www.british-history.ac.uk/commons-jrnl/vol11/pp456-457 |access-date=2023-04-29 |website=www.british-history.ac.uk}}</ref> and an act of parliament, the [Encouragement of Manufactures Act 1698](/source/Encouragement_of_Manufactures_Act_1698) ([11 Will. 3](/source/11_Will._3). c. 10), was passed that prohibited the wearing of printed calicos manufactured in China, India or Persia.<ref>{{Cite book |last=Pickering |first=Danby |url=https://archive.org/details/statutesatlarge31britgoog/page/328/mode/2up |title=Statutes at large 8 Gui III - 1 Ann (1696 - 1701) |date=1762 |publisher=Cambridge [London] |others=University of Michigan |volume=10 |location=Great Britain |pages=328–331}}</ref> This inadvertently established a calico bleaching and printing industry using unbleached Indian calico. A second law in 1721 prohibited the use and wear of all printed, painted, stained or dyed calicoes <ref>{{Cite book |last=Pickering |first=Danby |url=https://archive.org/details/dli.bengal.10689.22525/page/n343/mode/2up |title=The Statutes at Large 5 - 9 Geo 1 (1718 - 1721) |date=1765 |publisher=Joseph Bentham |volume=14 |location=Cambridge |pages=318–321}}</ref> which stimulated demand for [linen](/source/linen) and [fustian](/source/fustian). The [calico acts](/source/Calico_Acts) were repealed in 1774 when cloth was made using imported cotton from America.<ref>{{Cite book |last=Pickering |first=Danby |url=https://archive.org/details/statutesatlarge70britgoog/page/436/mode/2up |title=Statutes at large 13 - 14 Geo 3 (1773 - 1774) |date=1762 |publisher=Charles Bathurst |others=University of Michigan |volume=30 |location=Cambridge [London] |pages=437}}</ref>

=== Discovery of Chlorine ===
After discovering [Chlorine](/source/Chlorine) in the late 18th century, when chemical bleaching came into existence, the chemical bleaching rose above Grassing, as it was quicker and possible in indoors.<ref name=":03"/><ref name=":12"/><ref name=":23"/>

The French chemist [Claude Louis Berthollet](/source/Claude_Louis_Berthollet) first demonstrated the bleaching properties of chlorine and subsequently developed liquid bleaches around 1789. [James Watt](/source/James_Watt) is credited with bringing it to Britain, and a fellow Scot, [Charles Tennant](/source/Charles_Tennant) patented a more practical bleaching powder that made chlorine-based bleaching a commercial success.

==Scouring==
{{Main|Scouring (textiles)}}
Scouring is the first process carried out with or without [chemicals](/source/Chemical_substance), at room temperature or at suitable higher temperatures with the addition of suitable [wetting agent](/source/wetting_agent)s, [alkali](/source/alkali) and so on. Scouring removes the impurities such as [wax](/source/wax)es, [pectin](/source/pectin)s and makes the textile material [hydrophilic](/source/Hydrophile) or water absorbent.<ref name=":0">{{Cite book|url=https://archive.org/details/FacultyOfEngineeringEditingVersion|title=Faculty Of Engineering|pages=18|language=English}}</ref><ref name=":2">{{Cite book|last1=Horrocks|first1=A. Richard|url=https://books.google.com/books?id=QUqdBAAAQBAJ&q=%22Scouring%22+textiles+-wikipedia&pg=PA191|title=Handbook of Technical Textiles: Technical Textile Processes|last2=Anand|first2=Subhash C.|date=2015-12-01|publisher=Woodhead Publishing|isbn=978-1-78242-481-9|pages=191|language=en}}</ref><ref>{{Cite book|last=Trotman|first=E. R. (Edward Russell)|url=https://archive.org/details/textilescouringb0000trot|title=Textile scouring and bleaching|date=1968|location=London |publisher= Griffin|isbn=978-0-85264-067-8}}</ref>{{Rp|78}} Scouring is then followed by the bleaching process.<ref name=":4" />{{Rp|169}}<ref name=":4" />{{Rp|193}}

==Bleaching==
The term "bleach" originates from a French word signifying "to whiten". In essence, the process of bleaching involves whitening by removing substances that impart color to the material undergoing the bleaching treatment.<ref>{{Cite book |last1=O'Neill |first1=Charles |url=http://archive.org/details/dictionaryofdyei00oneiiala |title=A dictionary of dyeing and calico printing : containing a brief account of dyeing and printing textile fabrics |last2=Fesquet |first2=A. A. |date=1869 |publisher=Philadelphia : H.C. Baird |others=University of California Libraries}}</ref> Bleaching is the process of decolorizing the material after it has been scoured.<ref name=":4" />{{Rp|169}} Bleaching textiles can be classified as oxidative bleaching and reductive bleaching which can be carried out with oxidizing and reductive [bleaching agents](/source/Bleach).<ref>{{Cite book|last=Karmakar|first=S. R.|url=https://books.google.com/books?id=rc5yfbdbXr8C&q=Bleaching+of+textiles+can+be+classified+into+oxidative+bleaching+and+reductive+bleaching.&pg=PA161|title=Chemical Technology in the Pre-Treatment Processes of Textiles|date=1999-11-02|publisher=Elsevier|isbn=978-0-08-053947-8|language=en}}</ref>{{Rp|161}} Bleaching agents attack the [chromophore](/source/chromophore)s and alter the color absorbing properties of the objects.<ref>{{Cite web|title=Bleaching Agent - an overview {{!}} ScienceDirect Topics|url=https://www.sciencedirect.com/topics/chemistry/bleaching-agent#:~:text=Bleaching%20Agents-,Bleaching%20agents%20are%20formulations%20that%20whiten%20or%20lighten%20a%20substrate,and%20commercial%20and%20household%20laundering.|access-date=2021-08-01|website=www.sciencedirect.com}}</ref>{{bettersource|date=February 2026}}

===Oxidative bleaching===
Generally oxidative bleachings are carried out using [sodium hypochlorite](/source/sodium_hypochlorite), [sodium chlorite](/source/sodium_chlorite) or [sulfuric acid](/source/sulfuric_acid).

[Vegetable fibres](/source/Fiber_crop), [animal fiber](/source/animal_fiber)s, and [mineral fibres](/source/Fiber) are the three major types of [natural fiber](/source/natural_fiber)s. Natural fibers such as [cotton](/source/cotton), [ramie](/source/ramie), [jute](/source/jute), [wool](/source/wool), and regenerated fibers such as [bamboo](/source/bamboo) are all generally bleached with oxidative methods.<ref name=":3">{{Cite book|url=https://books.google.com/books?id=yBcS0XlQVE0C&q=Natural+fibres+like+cotton,+ramie,+jute,+wool,+bamboo+are+all+generally+bleached+with+oxidative+methods.|title=The Indian Textile Journal|date=2012|publisher=Indian Textile Journal Limited|pages=113|language=en}}</ref>

==== Oxygen bleaching action ====
It is the [conjugated double bonds](/source/Conjugated_system) of the substrate that makes the substrate capable of absorbing visible light. Hence, it looks yellower and need bleaching. When bleaching action carries out with oxygen, it removes the chromophoric sites and makes the cloths whiter. Oxygen is a degrading bleaching agent.{{cn|date=February 2026}} The major source of chemical bleaching is [Hydrogen peroxide](/source/Hydrogen_peroxide) {{chem|H|2|O|2}} that contains  a [single bond](/source/Covalent_bond), (–O–O–). When this breaks down it gives rise to very reactive oxygen specie, which is the active agent of the bleach. Around sixty percent of the world Hydrogen peroxide is used in chemical bleaching of textiles and wood pulp.<ref>{{Cite journal|last1=Hage|first1=Ronald|last2=Lienke|first2=Achim|date=2006|title=Applications of Transition-Metal Catalysts to Textile and Wood-Pulp Bleaching|url=https://onlinelibrary.wiley.com/doi/abs/10.1002/anie.200500525|journal=Angewandte Chemie International Edition|language=en|volume=45|issue=2|pages=206–222|doi=10.1002/anie.200500525|issn=1521-3773|pmid=16342123|url-access=subscription}}</ref>

===Reductive bleaching===
Reductive bleaching is done with [sodium hydrosulphite](/source/sodium_hydrosulphite), a powerful reducing agent. Fibres like [polyamide](/source/polyamide)s, [polyacrylics](/source/Polyacrylic_acid) and polyacetates can be bleached using reductive bleaching technology.<ref name=":3" />

=== Textile whitening ===
{{Main|Optical brightener}}

Bleaching of textiles may include an additional application of optical brighteners (OBAs). Optical brightening agents are chemical compounds that absorb [light](/source/light) in the [ultraviolet](/source/ultraviolet) and violet region (usually 340–370&nbsp;nm) of the [electromagnetic spectrum](/source/electromagnetic_spectrum), and re-emit light in the blue region (typically 420–470&nbsp;nm) by [fluorescence](/source/fluorescence). After scouring and bleaching, optical brightening agents are applied to make the textile material appear a more brilliant white. These OBAs are available in different tints such as [blue](/source/blue), [violet](/source/Violet_(color)) and [red](/source/red).<ref>{{Citation|last1=Smulders|first1=Eduard|title=Laundry Detergents|date=2007|url=https://onlinelibrary.wiley.com/doi/abs/10.1002/14356007.a08_315.pub2|encyclopedia=Ullmann's Encyclopedia of Industrial Chemistry|publisher=American Cancer Society|language=en|doi=10.1002/14356007.a08_315.pub2|isbn=978-3-527-30673-2|access-date=2021-08-01|last2=Rybinski|first2=Wolfgang von|last3=Sung|first3=Eric|last4=Rähse|first4=Wilfried|last5=Steber|first5=Josef|last6=Wiebel|first6=Frederike|last7=Nordskog|first7=Anette|url-access=subscription}}</ref>

== Whiteness ==
[[File:Canonization 2014-The Canonization of Saint John XXIII and Saint John Paul II (14036966125).jpg|thumb|right|[Pope Francis](/source/Pope_Francis) at the [Vatican](/source/Vatican_City).  Popes have traditionally worn white since 1566.]]
Whiteness in [colorimetry](/source/colorimetry) is the degree to which a surface is white.<ref>{{Cite book|title=Colorimetry : understanding the CIE system|date=2007|publisher=CIE/Commission internationale de l'eclairage|others=János Schanda, International Commission on Illumination|isbn=978-0-470-17563-7|location=Vienna, Austria|oclc=181346337}}</ref> The term "whiteness" refers to the degree to which a surface resembles the properties of a perfect reflecting diffuser, i.e. an ideal reflecting surface that neither absorbs nor transmits light, but instead reflects it evenly in all directions.<ref name=":5">{{Citation|last=Westland|first=Stephen|title=CIE Whiteness|date=2014|url=https://doi.org/10.1007/978-3-642-27851-8_5-1|encyclopedia=Encyclopedia of Color Science and Technology|pages=1–5|editor-last=Luo|editor-first=Ronnier|place=Berlin, Heidelberg|publisher=Springer|language=en|doi=10.1007/978-3-642-27851-8_5-1|isbn=978-3-642-27851-8|access-date=2021-08-01|url-access=subscription}}</ref>

=== CIE Whiteness ===
CIE Whiteness is a formula that measures the degree of whiteness.<ref name=":5" /> The CIE Whiteness Index is a measure or methodology developed by  the Commission on illumination.<ref>{{Cite book|last=Amutha|first=K.|url=https://books.google.com/books?id=sMn1CwAAQBAJ&dq=The+CIE+Whiteness+Index&pg=PA105|title=A Practical Guide to Textile Testing|date=2016-04-05|publisher=CRC Press|isbn=978-93-85059-62-9|pages=105|language=en}}</ref>

==Gallery==
<gallery mode="traditional">
File:Splendor Solis - Traité d'Alchimie - Femmes lavant le linge.jpg| Grassing, laying out linens to bleach in sunlight
File:Linen Bleach Green (8251136135).jpg| Linen bleaching/ grassing
File:Bleekveld.jpg|''Bleekveld in een dorp'' (''Bleachfield in a village''), circa 1650 ([Jan Brueghel the Younger](/source/Jan_Brueghel_the_Younger))
File:Jan Brueghel (I) and Joos de Momper (II) - Market and washing place in Flanders.jpg|Market and washing place in Flanders
File:Bleaching vats for cloth in the piece. Silk industry, South Manchester, Conn., U.S.A (NYPL b11707678-G90F070 026F).tiff|Bleaching vats for cloth in the piece
File:EB1911 Bleaching - Fig. 4. —High Pressure Blow-through Kier.jpg|High Pressure Blow-through Kier
File:EB1911 Bleaching - Fig. 5. —Roller Washing Machine.jpg|alt=Bleaching—Roller Washing Machine|Bleaching—The Mather Kier, cross section
File:EB1911 Bleaching - Fig. 6.—The Mather Kier, cross section.jpg|Bleaching—The Mather Kier, cross section
File:EB1911 Bleaching - Fig. 7.—The Mather Kier, longitudinal section.jpg|Bleaching—The Mather Kier, longitudinal section
File:EB1911 Bleaching - Fig. 8.—Mather & Platt’s Horizontal Drying Machine.jpg|Bleaching—Mather & Platt’s Horizontal Drying Machine
File:EB1911 Bleaching - Fig. 9.—Horizontal Drying Machine threaded with Cloth.jpg|Bleaching—Horizontal Drying Machine threaded with Cloth
</gallery>

== See also ==

* [White](/source/White)
*[Dyeing](/source/Dyeing)
* [Color of clothing](/source/Color_of_clothing)
*[Color temperature](/source/Color_temperature)
*[History of cotton](/source/History_of_cotton)

== References ==
{{Reflist}}

==External links==
{{EB1911 poster|Bleaching}}
* [https://web.archive.org/web/20110725093823/http://www.thesmarttime.com/ Textile Processing Guide] at thesmarttime.com

{{DEFAULTSORT:Textile Bleaching}}
Category:Textiles
Category:Industrial processes
Category:Textile techniques

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Adapted from the Wikipedia article [Textile bleaching](https://en.wikipedia.org/wiki/Textile_bleaching) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Textile_bleaching?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.