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

wood staining Wood stain is a type of paint used to colour wood and consists of colourants dissolved and/or suspended in a 'vehicle' or solvent. Vehicle is the preferred term, as the contents of a stain may not be truly dissolved in the vehicle, but rather ...

, rust staining and

stained glass Stained glass is coloured glass as a material or works created from it. Throughout its thousand-year history, the term has been applied almost exclusively to the windows of churches and other significant religious buildings. Although tradition ...

Types

There can be intentional stains (such as wood stains or paint), indicative stains (such as

food coloring Food coloring, or color additive, is any dye, pigment, or substance that imparts color when it is added to food or drink. They come in many forms consisting of liquids, powders, gels, and pastes. Food coloring is used in both commercial food ...

or adding a substance to make bacteria visible under a microscope), natural stains (such as

rust Rust is an iron oxide, a usually reddish-brown oxide formed by the reaction of iron and oxygen in the catalytic presence of water or air moisture. Rust consists of hydrous iron(III) oxides (Fe2O3·nH2O) and iron(III) oxide-hydroxide (FeO(OH) ...

on iron or a patina on

bronze Bronze is an alloy consisting primarily of copper, commonly with about 12–12.5% tin and often with the addition of other metals (including aluminium, manganese, nickel, or zinc) and sometimes non-metals, such as phosphorus, or metalloids such ...

), and accidental stains such as

ketchup Ketchup or catsup is a table condiment with a sweet and tangy flavor. The unmodified term ("ketchup") now typically refers to tomato ketchup, although early recipes used egg whites, mushrooms, oysters, grapes, mussels, or walnuts, among oth ...

and

synthetic oil Synthetic oil is a lubricant consisting of chemical compounds that are artificially modified or synthesised. Synthetic lubricants can be manufactured using chemically modified petroleum components rather than whole crude oil, but can also be syn ...

on clothing. Different types of material can be stained by different substances, and stain resistance is an important characteristic in modern textile engineering. Waistcoat, naval (AM 2015

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. The material that is trapped coats the underlying material, and the stain reflects back light according to its own color. Applying paint, spilled food, and wood stains are of this nature. 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. Finally, there can also be molecular attraction between the material and the staining material, involving being held in a

covalent bond A covalent bond is a chemical bond that involves the sharing of electrons to form electron pairs between atoms. These electron pairs are known as shared pairs or bonding pairs. The stable balance of attractive and repulsive forces between atom ...

and showing the color of the bound substance.

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 Ironing is the use of a machine, usually a heated tool (an iron), to remove wrinkles and unwanted creases from fabric. The heating is commonly done to a temperature of 180–220 °Celsius (356-428 Fahrenheit), depending on the fabric. Ironing wor ...

, dry cleaning or sunlight, can cause a chemical reaction on an otherwise removable stain, turning it into a chemical.

Removal

Various

laundry Laundry refers to the washing of clothing and other textiles, and, more broadly, their drying and ironing as well. Laundry has been part of history since humans began to wear clothes, so the methods by which different cultures have dealt with ...

techniques exist to attempt to remove or reduce existing stains. Stain remover is an important type of chemical in laundry detergents and some removers are formulated to be applied directly onto stains. The removal of some stains require other chemicals or special techniques. Use of an inappropriate technique could make permanent an otherwise removable stain or cause unwanted discolouration of the clothing.Solutions for Clothing and Laundry Stain Removal
/ref> Information about stain removal can be found in magazines,

books A book is a medium for recording information in the form of writing or images, typically composed of many pages (made of papyrus, parchment, vellum, or paper) bound together and protected by a cover. The technical term for this physical a ...

advertisements Advertising is the practice and techniques employed to bring attention to a product or service. Advertising aims to put a product or service in the spotlight in hopes of drawing it attention from consumers. It is typically used to promote a ...

or online:
Stain removal guide

American Cleaning Institute The American Cleaning Institute (ACI formerly The Soap and Detergent Association – SDA) is an organization representing producers of household, industrial, and institutional cleaning products, their ingredients and finished packaging; oleochemic ...

Stain solutions

University of Illinois The University of Illinois Urbana-Champaign (U of I, Illinois, University of Illinois, or UIUC) is a public land-grant research university in Illinois in the twin cities of Champaign and Urbana. It is the flagship institution of the Universi ...

* Stain removal advice from Procter & Gamble
UKCanada

References

External links

* * {{Laundry navbox Laundry Artistic techniques