Stain

{{Short description|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}}

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>

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 permanently unclean. Intentional staining is used in biochemical research, and for artistic effect, such as in wood staining, rust staining and stained glass.

==Types== There can be intentional stains (such as wood stains 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 fabrics 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 captain of the Victorian era]]

thumb|Coffee stains

==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 structures 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 stains 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 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== Various laundry techniques exist to attempt to remove or reduce existing stains. Stain removal is frequently a highly desired characteristic in laundry detergents and other types of cleaning products. Some products are designed to be applied directly onto stains. The removal of some types of stains requires chemicals or special techniques.<ref>{{Cite web |title=Stain Removal Guide |url=https://www.cleaninginstitute.org/cleaning-tips/clothes/stain-removal-guide |access-date=8 August 2025 |website=American Cleaning Institute}}</ref>

Some techniques for wood stain removal, involve first removing the protective layer (for example varnish) if there is one, before sanding and refinishing.<ref>{{Cite web |title=How to Remove Stain From Wood |url=https://www.thespruce.com/how-to-remove-stain-from-wood-6749848 |access-date=2025-08-08 |website=The Spruce |language=en}}</ref>

There are different techniques for removing rust stains, depending on the material this is on, for example clothing or concrete. Some housekeeping guides recommend using salt and lemon juice on clothing and specialist cleaners to remove rust from concrete, on areas such as driveways and patios.<ref>{{Cite web |last=Helen |first=McCue |date=8 April 2021 |title=How to remove rust and iron mould stains |url=https://www.goodhousekeeping.com/uk/house-and-home/household-advice/a656980/remove-rust-and-iron-mould-stains/ |access-date=2025-08-08 |website=Good Housekeeping |language=en-GB}}</ref>

==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 * {{wiktionary inline}} * {{commons inline}} {{Laundry navbox}}

Category:Laundry Category:Artistic techniques Category:Materials science Category:Textiles