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 Unclean may refer to: * Unclean animals, those whose consumption or handling is labeled a taboo * Unclean food, in Jewish dietary custom * Ritually impure, in various religions * Unclean hands, a term in contract law * ''Unclean'' (album), a 19 ...

. 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 Paint is any pigmented liquid, liquefiable, or solid mastic composition that, after application to a substrate in a thin layer, converts to a solid film. It is most commonly used to protect, color, or provide texture. Paint can be made in many ...

), indicative stains (such as food coloring or adding a substance to make bacteria visible under a microscope), natural stains (such as rust on iron or a

patina Patina ( or ) is a thin layer that variously forms on the surface of copper, brass, bronze and similar metals and metal alloys (tarnish produced by oxidation or other chemical processes) or certain stones and wooden furniture (sheen produced b ...

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 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 atoms ...

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, dry cleaning or

sunlight Sunlight is a portion of the electromagnetic radiation given off by the Sun, in particular infrared, visible, and ultraviolet light. On Earth, sunlight is scattered and filtered through Earth's atmosphere, and is obvious as daylight when t ...

, 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 t ...

techniques exist to attempt to remove or reduce existing stains.

Stain remover Stain removal is the process of removing a mark or spot left by one substance on a specific surface like a fabric. A solvent or detergent is generally used to conduct stain removal and many of these are available over the counter. Stain preventi ...

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 ar ...

, advertisements 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 * Stain removal advice from Procter & Gamble
UKCanada

References

External links

* * {{Laundry navbox Laundry Artistic techniques