View source for Stain

{{Short description|A discoloration that can be clearly distinguished from the surface}}
{{For-multi|stains in woodworking|Wood stain|the scientific and medical technique|Staining|other uses}}
{{redirect|Stained|the band|Staind}}
[[File:Brązowe plamy ubt.jpeg|thumb|Coffee stains]]
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A '''stain''' is a discoloration that can be clearly distinguished from the surface, material, or medium it is found upon. They are caused by the chemical or physical interaction of two dissimilar materials. Accidental staining may make [[materials]] appear used, degraded or [[Cleanliness|permanently unclean]]. Intentional [[staining]] is used in biochemical research, and for artistic effect, such as in [[wood staining]], [[weathering steel|rust staining]] and [[stained glass]].

==Types==
There can be intentional stains (such as [[wood stain]]s or [[paint]]),<ref name="stainbook">{{cite journal | title = Understanding Wood Finishing: How to Select and Apply the Right Finish | author = Bob Flexner | journal = Reader's Digest | date = 1999 | pages = 121 | isbn = 978-0-7621-0191-7}}</ref> indicative stains (such as [[food coloring]] dye, and [[staining]], the use of one or more substances to enhance visibility of samples in a [[microscope]] or other imaging device.<ref>{{Cite book | title = Staining Procedures Used by the Biological Stain Commission: Published for the Biological Stain Commission | author = George Clark, James W. Bartholomew | publisher = Williams & Wilkins | date = 1981 | pages = 32–33 | isbn = 978-0-683-01707-6}}</ref> Numerous naturally-occurring stains exist, such as [[rust]] on iron and a [[patina]] on [[bronze]],<ref>{{cite book | title = Architectural Metals: A Guide to Selection, Specification, and Performance | author = L. William Zahner | author-link = L. William Zahner | publisher = Wiley | date = 1997 | page = 101 | isbn = 978-0-471-04506-9}}</ref> as do accidental stains such as from [[ketchup]] and [[oil]] on [[fabric]]s and other materials.

Different types of material can be stained by different substances, and stain resistance is an important characteristic in modern [[textile engineering]].{{citation needed|date=June 2023}}

[[File:Waistcoat, naval (AM 2015.38.1.3-5).jpg|thumb|Stained [[waistcoat]], originally that of a [[Royal Navy ranks, rates, and uniforms of the 18th and 19th centuries|Royal Navy captain]] of the [[Victorian era]]]]

[[File:Patternspage.jpg|thumb|From a copy of "Decorative Patterns of the Ancient world," by Sir Flinders Petrie.<ref name="Internet Archive 2023 g798">{{cite web | title=Decorative patterns of the Ancient World : Flinders, Petrie : Free Download, Borrow, and Streaming : Internet Archive | website=Internet Archive | date=2023-03-25 | url=https://archive.org/details/in.gov.ignca.39205/page/n109/mode/2up?view=theater | access-date=2024-02-17}}</ref>]]

==Formation==
The primary method of stain formation is surface stains, where the staining substance is spilled out onto the surface or material and is trapped in the fibers, pores, indentations, or other [[capillary action|capillary structure]]s on the surface.<ref name="stainbook" /> The material that is trapped coats the underlying material, and the stain reflects backlight according to its own color. Applied paint, spilled food, and [[wood stain]]s are of this nature.<ref>{{cite book | title = Materials Performance | author = NACE International | publisher = National Association of Corrosion Engineers | date = 1987 | volume = 26 | page = 33}}</ref>

A secondary method of stain involves a [[chemical reaction|chemical]] or molecular reaction between the material and the staining material. Many types of natural stains fall into this category.{{citation needed|date=June 2023}}

Finally, there can also be molecular attraction between the material and the staining material, involving being held in a [[covalent bond]] and showing the color of the bound substance.<ref name="stainbook2">{{cite book | title = The Stain Removal Handbook | author = Max Alth, Simon Alth | publisher = Hawthorn Books | date = 1977 | page = [https://archive.org/details/stainremovalhand0000alth/page/22 22] | isbn = 978-0-8015-7071-1 | url-access = registration | url = https://archive.org/details/stainremovalhand0000alth/page/22 }}</ref>{{fv|date=April 2025}}

==Properties==
In many cases, stains are affected by [[heat]] and may become reactive enough to bond with the underlying material. Applied heat, such as from [[ironing]], [[dry cleaning]], or [[sunlight]], can cause a chemical reaction on an otherwise removable stain.{{fact|date=April 2025}}

==Removal==
{{Expand section|removal from things besides clothing|section=4|date=August 2024}}
Various [[laundry]] techniques exist to attempt to remove or reduce existing stains. [[Stain removal]] is frequently a highly desired characteristic in [[laundry detergent]]s and other types of cleaning agent. Some agents are designed to be applied directly onto stains. The removal of some types of stains requires other chemicals or special techniques. Use of an inappropriate technique could make permanent an otherwise removable stain or cause unwanted discoloration of clothing.<ref>[http://www.laundrycares.com/laundry-stain-removal/ Solutions for Clothing and Laundry Stain Removal]</ref>

==See also==
*[[Biodegradation]]
*[[Bleach]]
*[[Dye]]
*[[Foxing]]
*[[Permanent marker]]
*[[Weathering steel]]

==References==
{{Reflist}}

==Further reading==
*Stain & Spot Removal Handbook: Consumer guide. by the editors of [[Consumer Guide]]. Skokie, Ill: Beekman House, 1981. 9780517316832
*Zia, Stephanie. Stain Removal. London: Hamlyn, 2005. Distributed in the U.S. and Canada by Sterling Pub. Co., 2005. 9780600611240
*Soto, Anne Marie''Stain Rescue!: The A-Z Guide to Removing Smudges, Spots & Other Spills'' By good Housekeeping Institute (New York, N.Y.). Published by Sterling Publishing Company, 2007 ISBN
* Mendelson, Cheryl ''Laundry: The Home Comforts Book of Caring for Clothes and Linens'' Simon & Schuster, 2005 {{ISBN|978-0-7432-7145-5}}

==External links==
* [https://www.cleaninginstitute.org/cleaning-tips/clothes/stain-removal-guide Stain removal guide], [[American Cleaning Institute]]
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[[Category:Laundry]]
[[Category:Artistic techniques]]
[[Category:Materials science]]
[[Category:Textiles]]