Paint is any pigmented
liquid
A liquid is a nearly incompressible fluid that conforms to the shape of its container but retains a (nearly) constant volume independent of pressure. As such, it is one of the four fundamental states of matter (the others being solid, gas, a ...
, liquefiable, or solid
mastic composition that, after application to a
substrate in a thin layer, converts to a
solid
Solid is one of the State of matter#Four fundamental states, four fundamental states of matter (the others being liquid, gas, and Plasma (physics), plasma). The molecules in a solid are closely packed together and contain the least amount o ...
film. It is most commonly used to protect, color, or provide texture. Paint can be made in many colors—and in many different types. Paint is typically stored, sold, and applied as a liquid, but most types dry into a solid. Most paints are either oil-based or water-based and each has distinct characteristics. For one, it is illegal in most municipalities to discard oil-based paint down household drains or sewers. Clean-up solvents are also different for water-based paint than they are for oil-based paint. Water-based paints and oil-based paints will cure differently based on the outside ambient temperature of the object being painted (such as a house.) Usually, the object being painted must be over , although some manufacturers of external paints/primers claim they can be applied when temperatures are as low as .
History
![Lascaux, Megaloceros](https://upload.wikimedia.org/wikipedia/commons/1/1d/Lascaux%2C_Megaloceros.jpg)
Paint was one of the earliest arts of humanity. Some
cave paintings drawn with red or yellow
ochre
Ochre ( ; , ), or ocher in American English, is a natural clay earth pigment, a mixture of ferric oxide and varying amounts of clay and sand. It ranges in colour from yellow to deep orange or brown. It is also the name of the colours produced ...
,
hematite
Hematite (), also spelled as haematite, is a common iron oxide compound with the formula, Fe2O3 and is widely found in rocks and soils. Hematite crystals belong to the rhombohedral lattice system which is designated the alpha polymorph of . ...
,
manganese oxide Manganese oxide is any of a variety of manganese oxides and hydroxides.Wells A.F. (1984) ''Structural inorganic chemistry'' 5th edition Oxford Science Publications, . These include
* Manganese(II) oxide, MnO
* Manganese(II,III) oxide, Mn3O4
* Mang ...
, and
charcoal
Charcoal is a lightweight black carbon residue produced by strongly heating wood (or other animal and plant materials) in minimal oxygen to remove all water and volatile constituents. In the traditional version of this pyrolysis process, cal ...
may have been made by early ''
Homo sapiens
Humans (''Homo sapiens'') are the most abundant and widespread species of primate, characterized by bipedalism and exceptional cognitive skills due to a large and complex brain. This has enabled the development of advanced tools, culture, ...
'' as long as 40,000 years ago. Paint may be even older. In 2003 and 2004, South African archeologists reported finds in
Blombos Cave of a 100,000-year-old human-made
ochre
Ochre ( ; , ), or ocher in American English, is a natural clay earth pigment, a mixture of ferric oxide and varying amounts of clay and sand. It ranges in colour from yellow to deep orange or brown. It is also the name of the colours produced ...
-based mixture that could have been used like paint.
Further excavation in the same cave resulted in the 2011 report of a complete toolkit for grinding pigments and making a primitive paint-like substance.
[
Interior walls at the 5,000-year-old ]Ness of Brodgar
The Ness of Brodgar is an archaeological site covering between the Ring of Brodgar and the Stones of Stenness in the Heart of Neolithic Orkney World Heritage Site in Orkney, Scotland. Excavations at the site began in 2003. The site has provide ...
have been found to incorporate individual stones painted in yellows, reds, and oranges, using ochre pigment made of haematite mixed with animal fat, milk or eggs.
Ancient colored walls at Dendera
Dendera ( ar, دَنْدَرة ''Dandarah''; grc, Τεντυρις or Τεντυρα; Bohairic cop, ⲛⲓⲧⲉⲛⲧⲱⲣⲓ, translit=Nitentōri; Sahidic cop, ⲛⲓⲧⲛⲧⲱⲣⲉ, translit=Nitntōre), also spelled ''Denderah'', ancient ...
, Egypt
Egypt ( ar, مصر , ), officially the Arab Republic of Egypt, is a transcontinental country spanning the northeast corner of Africa and southwest corner of Asia via a land bridge formed by the Sinai Peninsula. It is bordered by the Mediter ...
, which were exposed for years to the elements, still possess their brilliant color, as vivid as when they were painted about 2,000 years ago. The Egyptians mixed their colors with a gummy substance and applied them separately from each other without any blending or mixture. They appear to have used six colors: white, black, blue, red, yellow, and green. They first covered the area entirely with white, then traced the design in black, leaving out the lights of the ground color. They used minium
''Minium'' is a genus of thalloid alga
Algae (; singular alga ) is an informal term for a large and diverse group of photosynthetic eukaryotic organisms. It is a polyphyletic grouping that includes species from multiple distinct clades. I ...
for red, generally of a dark tinge.
The oldest known oil paintings are Buddhist murals created circa 650 AD. The works are located in cave-like rooms carved from the cliffs of Afghanistan's Bamiyan Valley
Bamyan or Bamyan Valley (); ( prs, بامیان) also spelled Bamiyan or Bamian is the capital of Bamyan Province in central Afghanistan. Its population of approximately 70,000 people makes it the largest city in Hazarajat. Bamyan is at an alti ...
, "using walnut and poppy seed oils." Pliny mentions some painted ceilings in his day in the town of Ardea, which had been made prior to the foundation of Rome
, established_title = Founded
, established_date = 753 BC
, founder = King Romulus (legendary)
, image_map = Map of comune of Rome (metropolitan city of Capital Rome, region Lazio, Italy).svg
, map_caption ...
. He expressed great surprise and admiration at their freshness, after the lapse of so many centuries.
In the 13th century, oil was used to detail tempera paintings. In the 14th century, Cennino Cennini described a painting technique utilizing tempera painting
Tempera (), also known as egg tempera, is a permanent, fast-drying painting medium consisting of colored pigments mixed with a water-soluble binder medium, usually glutinous material such as egg yolk. Tempera also refers to the paintings done ...
covered by light layers of oil. The slow-drying properties of organic oils were commonly known to early European painters. However, the difficulty in acquiring and working the materials meant that they were rarely used (and indeed the slow drying was seen as a disadvantage). Paint was made with the yolk of eggs and therefore, the substance would harden and adhere to the surface it was applied to. Pigment was made from plants, sand, and different soils. Most paints used either oil or water as a base (the diluent, solvent or vehicle for the pigment).
The Flemish-trained or influenced Antonello da Messina, who Vasari
Giorgio Vasari (, also , ; 30 July 1511 – 27 June 1574) was an Italian Renaissance Master, who worked as a painter, architect, engineer, writer, and historian, who is best known for his work ''The Lives of the Most Excellent Painters, Sculpt ...
wrongly credited with the introduction of oil paint to Italy, does seem to have improved the formula by adding litharge
Litharge (from Greek lithargyros, lithos (stone) + argyros (silver) ''λιθάργυρος'') is one of the natural mineral forms of lead(II) oxide, PbO. Litharge is a secondary mineral which forms from the oxidation of galena ores. It forms as coa ...
, or lead (II) oxide. A still extant example of 17th-century house oil painting is Ham House in Surrey
Surrey () is a ceremonial and non-metropolitan county in South East England, bordering Greater London to the south west. Surrey has a large rural area, and several significant urban areas which form part of the Greater London Built-up Area. ...
, England
England is a country that is part of the United Kingdom. It shares land borders with Wales to its west and Scotland to its north. The Irish Sea lies northwest and the Celtic Sea to the southwest. It is separated from continental Europe b ...
, where a primer was used along with several undercoats and an elaborate decorative overcoat; the pigment and oil mixture would have been ground into a paste with a mortar and pestle. The process was done by hand by the painters, which exposed them to lead poisoning
Lead poisoning, also known as plumbism and saturnism, is a type of metal poisoning caused by lead in the body. The brain is the most sensitive. Symptoms may include abdominal pain, constipation, headaches, irritability, memory problems, inferti ...
, due to the white-lead powder.
In 1718, Marshall Smith invented a "Machine or Engine for the Grinding of Colours" in England. It is not known precisely how it operated, but it was a device that increased the efficiency of pigment grinding dramatically. Soon, a company called Emerton and Manby was advertising exceptionally low-priced paints that had been ground with labor-saving technology:
By the proper onset of the Industrial Revolution
The Industrial Revolution was the transition to new manufacturing processes in Great Britain, continental Europe, and the United States, that occurred during the period from around 1760 to about 1820–1840. This transition included going f ...
, in the mid-18th century, paint was being ground in steam-powered mills, and an alternative to lead-based pigments had been found in a white derivative of zinc oxide. Interior house painting increasingly became the norm as the 19th century progressed, both for decorative reasons and because the paint was effective in preventing the walls rotting from damp. Linseed oil was also increasingly used as an inexpensive binder.
In 1866, Sherwin-Williams in the United States
The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territorie ...
opened as a large paint-maker and invented a paint that could be used from the tin without preparation.
It was not until the stimulus of World War II
World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposin ...
created a shortage of linseed oil in the supply market that artificial resins, or alkyds, were invented. Cheap and easy to make, they also held the color well and lasted for a long time.
Components
Vehicle
The vehicle is composed of the binder; or, if it is necessary to thin the binder with a diluent like solvent or water, it is the combination of binder and diluent. In this case, once the paint has dried or cured very nearly all of the diluent has evaporated and only the binder is left on the coated surface. Thus, an important quantity in coatings formulation is the "vehicle solids", sometimes called the "resin solids" of the formula. This is the proportion of the wet coating weight that is binder, i.e. the polymer backbone of the film that will remain after drying or curing is complete. The volume of paint after it has dried, therefore only leaving the solids, is expressed as the volume solid Volume solid is the volume of paint after it has dried. This is different than the weight solid. Paint may contain solvent, resin, pigment
A pigment is a colored material that is completely or nearly insoluble in water. In contrast, dyes are typi ...
.
Binder or film former
The binder is the film-forming component of paint. It is the only component that is always present among all the various types of formulations. Many binders are too thick to be applied and must be thinned. The type of thinner, if present, varies with the binder.
The binder imparts properties such as gloss, durability, flexibility, and toughness.
Binders include synthetic or natural resins such as alkyd
An alkyd is a polyester resin modified by the addition of fatty acids and other components. Alkyds are derived from polyols and organic acids including dicarboxylic acids or carboxylic acid anhydride and triglyceride oils. The term ''alkyd'' is a m ...
s, acrylic
Acrylic may refer to:
Chemicals and materials
* Acrylic acid, the simplest acrylic compound
* Acrylate polymer, a group of polymers (plastics) noted for transparency and elasticity
* Acrylic resin, a group of related thermoplastic or thermosett ...
s, vinyl-acrylics, vinyl acetate/ethylene (VAE), polyurethanes, polyester
Polyester is a category of polymers that contain the ester functional group in every repeat unit of their main chain. As a specific material, it most commonly refers to a type called polyethylene terephthalate (PET). Polyesters include natural ...
s, melamine resin
Melamine resin or melamine formaldehyde (also shortened to melamine) is a resin with melamine rings terminated with multiple hydroxyl groups derived from formaldehyde. This thermosetting plastic material is made from melamine and formaldehyde. ...
s, epoxy
Epoxy is the family of basic components or cured end products of epoxy resins. Epoxy resins, also known as polyepoxides, are a class of reactive prepolymers and polymers which contain epoxide groups. The epoxide functional group is also coll ...
, silanes or siloxanes or oils.
Binders can be categorized according to the mechanisms for film formation. Thermoplastic mechanisms include drying and coalescence. Drying refers to simple evaporation of the solvent or thinner to leave a coherent film behind. Coalescence refers to a mechanism that involves drying followed by actual interpenetration and fusion of formerly discrete particles. Thermoplastic film-forming mechanisms are sometimes described as "thermoplastic cure" but that is a misnomer because no chemical curing reactions are required to knit the film. Thermosetting mechanisms, on the other hand, are true curing mechanism that involve chemical reaction(s) among the polymers that make up the binder.
Thermoplastic mechanisms: Some films are formed by simple cooling of the binder. For example, encaustic or wax
Waxes are a diverse class of organic compounds that are lipophilic, malleable solids near ambient temperatures. They include higher alkanes and lipids, typically with melting points above about 40 °C (104 °F), melting to give low ...
paints are liquid when warm, and harden upon cooling. In many cases, they re-soften or liquify if reheated.
Paints that dry by solvent evaporation and contain the solid binder dissolved in a solvent are known as lacquers. A solid film forms when the solvent evaporates. Because no chemical crosslinking is involved, the film can re-dissolve in solvent; as such, lacquers are unsuitable for applications where chemical resistance is important. Classic nitrocellulose
Nitrocellulose (also known as cellulose nitrate, flash paper, flash cotton, guncotton, pyroxylin and flash string, depending on form) is a highly flammable compound formed by nitrating cellulose through exposure to a mixture of nitric acid and ...
lacquers fall into this category, as do non-grain raising stains composed of dyes
A dye is a colored substance that chemically bonds to the substrate to which it is being applied. This distinguishes dyes from pigments which do not chemically bind to the material they color. Dye is generally applied in an aqueous solution and ...
dissolved in solvent. Performance varies by formulation, but lacquers generally tend to have better UV resistance and lower corrosion resistance than comparable systems that cure by polymerization or coalescence.
The paint type known as Emulsion
An emulsion is a mixture of two or more liquids that are normally immiscible (unmixable or unblendable) owing to liquid-liquid phase separation. Emulsions are part of a more general class of two-phase systems of matter called colloids. Althoug ...
in the UK and Latex
Latex is an emulsion (stable dispersion) of polymer microparticles in water. Latexes are found in nature, but synthetic latexes are common as well.
In nature, latex is found as a milky fluid found in 10% of all flowering plants (angiosperms ...
in the United States is a water-borne dispersion of sub-micrometer polymer particles. These terms in their respective countries cover all paints that use synthetic polymers such as acrylic, vinyl acrylic ( PVA), styrene acrylic, etc. as binders. The term "latex" in the context of paint in the United States simply means an aqueous dispersion; latex
Latex is an emulsion (stable dispersion) of polymer microparticles in water. Latexes are found in nature, but synthetic latexes are common as well.
In nature, latex is found as a milky fluid found in 10% of all flowering plants (angiosperms ...
rubber from the rubber tree is not an ingredient. These dispersions are prepared by emulsion polymerization. Such paints cure by a process called coalescence where first the water, and then the trace, or coalescing, solvent, evaporate and draw together and soften the binder particles and fuse them together into irreversibly bound networked structures, so that the paint cannot redissolve in the solvent/water that originally carried it. The residual surfactants in paint
Paint has four major components: pigments, binders, solvents, and additives. Pigments serve to give paint its color, texture, toughness, as well as determining if a paint is opaque or not. Common white pigments include titanium dioxide and zinc oxi ...
, as well as hydrolytic
Hydrolysis (; ) is any chemical reaction in which a molecule of water breaks one or more chemical bonds. The term is used broadly for substitution, elimination, and solvation reactions in which water is the nucleophile.
Biological hydrolysis ...
effects with some polymers cause the paint to remain susceptible to softening and, over time, degradation by water. The general term of latex paint is usually used in the United States, while the term emulsion paint is used for the same products in the UK and the term latex paint is not used at all.
Thermosetting mechanisms: Paints that cure by polymerization are generally one- or two-package coatings that polymerize by way of a chemical reaction, and cure into a cross-linked film. Depending on composition they may need to dry first, by evaporation of solvent. Classic two-package epoxies
The Epoxies were an American New wave music, new wave band from Portland, Oregon, formed in 2000. Heavily influenced by new wave, the band jokingly described themselves as robot garage rock. Members included FM Static on synthesizers, guitarist ...
or polyurethanes would fall into this category.[Berendsen, A. M., & Berendsen, A. M. (1989). ''Marine painting manual''. London: Graham & Trotman. p. 114.]
The "drying oils", counter-intuitively, actually cure by a crosslinking reaction even if they are not put through an oven cycle and seem to simply dry in air. The film formation mechanism of the simplest examples involve first evaporation of solvents followed by reaction with oxygen from the environment over a period of days, weeks and even months to create a crosslinked network. Classic alkyd
An alkyd is a polyester resin modified by the addition of fatty acids and other components. Alkyds are derived from polyols and organic acids including dicarboxylic acids or carboxylic acid anhydride and triglyceride oils. The term ''alkyd'' is a m ...
enamels would fall into this category. Oxidative cure coatings are catalyzed by metal complex driers such as cobalt naphthenate
Cobalt(II) naphthenate is a mixture of cobalt(II) derivatives of naphthenic acids. These coordination complexes are widely used as oil drying agents for the autoxidative crosslinking of drying oils. Metal naphthenates are not well defined in con ...
though cobalt octoate is more common.
Recent environmental requirements restrict the use of volatile organic compound
Volatile organic compounds (VOCs) are organic compounds that have a high vapour pressure at room temperature. High vapor pressure correlates with a low boiling point, which relates to the number of the sample's molecules in the surrounding air, a ...
s (VOCs), and alternative means of curing have been developed, generally for industrial purposes. UV curing paints, for example, enable formulation with very low amounts of solvent, or even none at all. This can be achieved because of the monomers and oligomers used in the coating have relatively very low molecular weight, and are therefore low enough in viscosity to enable good fluid flow without the need for additional thinner. If solvent is present in significant amounts, generally it is mostly evaporated first and then crosslinking is initiated by ultraviolet light. Similarly, powder coatings contain little or no solvent. Flow and cure are produced by the heating of the substrate after electrostatic application of the dry powder.
Combination mechanisms: So-called "catalyzed" lacquers" or "crosslinking latex" coatings are designed to form films by a combination of methods: classic drying plus a curing reaction that benefits from the catalyst. There are paints called plastisols/organosols, which are made by blending PVC granules with a plasticiser. These are stoved and the mix coalesces.
Diluent or solvent or thinner
The main purposes of the diluent are to dissolve the polymer and adjust the viscosity
The viscosity of a fluid is a measure of its resistance to deformation at a given rate. For liquids, it corresponds to the informal concept of "thickness": for example, syrup has a higher viscosity than water.
Viscosity quantifies the inte ...
of the paint. It is volatile and does not become part of the paint film. It also controls flow and application properties, and in some cases can affect the stability of the paint while in liquid state. Its main function is as the carrier for the non-volatile components. To spread heavier oils (for example, linseed) as in oil-based interior house paint, a thinner oil is required. These volatile substances impart their properties temporarily—once the solvent has evaporated, the remaining paint is fixed to the surface.
This component is optional: some paints have no diluent.
Water is the main diluent for water-borne paints, even the co-solvent types.
Solvent-borne, also called oil-based, paints can have various combinations of organic solvents as the diluent, including aliphatics, aromatics, alcohol
Alcohol most commonly refers to:
* Alcohol (chemistry), an organic compound in which a hydroxyl group is bound to a carbon atom
* Alcohol (drug), an intoxicant found in alcoholic drinks
Alcohol may also refer to:
Chemicals
* Ethanol, one of sev ...
s, ketone
In organic chemistry, a ketone is a functional group with the structure R–C(=O)–R', where R and R' can be a variety of carbon-containing substituents. Ketones contain a carbonyl group –C(=O)– (which contains a carbon-oxygen double bo ...
s and white spirit
White spirit (AU, UK & Ireland)Primarily in the United Kingdom and Australia. In New Zealand "white spirit" can also refer to Coleman fuel (white gas). or mineral spirits (US, Canada), also known as mineral turpentine (AU/NZ), turpentine substitu ...
. Specific examples are organic solvents such as petroleum distillate
Petrochemicals (sometimes abbreviated as petchems) are the chemical products obtained from petroleum by refining. Some chemical compounds made from petroleum are also obtained from other fossil fuels, such as coal or natural gas, or renewable sou ...
, ester
In chemistry, an ester is a compound derived from an oxoacid (organic or inorganic) in which at least one hydroxyl group () is replaced by an alkoxy group (), as in the substitution reaction of a carboxylic acid and an alcohol. Glycerides ar ...
s, glycol ethers, and the like. Sometimes volatile low-molecular weight synthetic resins also serve as diluents.
Pigment, dye and filler
Pigments are granular solids incorporated in the paint to contribute color. Dyes are colorants that dissolve in the paint. Fillers are granular solids incorporated to impart toughness, texture, give the paint special properties, or to reduce the cost of the paint. During production, the size of such particles can be measured with a Hegman gauge A Hegman gauge, sometimes referred to as a grind gauge, grind gage, or grindometer, is an instrument which indicates the fineness of grind or the presence of coarse particles and agglomeration in a dispersion. It is commonly used to determine how fi ...
. Rather than using only solid particles, some paints contain dye
A dye is a colored substance that chemically bonds to the substrate to which it is being applied. This distinguishes dyes from pigments which do not chemically bind to the material they color. Dye is generally applied in an aqueous solution an ...
s instead of or in combination with pigments.
Pigments can be classified as either natural or synthetic. Natural pigments include various clay
Clay is a type of fine-grained natural soil material containing clay minerals (hydrous aluminium phyllosilicates, e.g. kaolin, Al2 Si2 O5( OH)4).
Clays develop plasticity when wet, due to a molecular film of water surrounding the clay par ...
s, calcium carbonate, mica
Micas ( ) are a group of silicate minerals whose outstanding physical characteristic is that individual mica crystals can easily be split into extremely thin elastic plates. This characteristic is described as perfect basal cleavage. Mica is ...
, silica
Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula , most commonly found in nature as quartz and in various living organisms. In many parts of the world, silica is the major constituent of sand. Silica is one ...
s, and talcs. Synthetics would include engineered molecules, calcined clays, blanc fixe
Barium sulfate (or sulphate) is the inorganic compound with the chemical formula Barium, BaSulfate, SO4. It is a white crystalline solid that is odorless and Solubility, insoluble in water. It occurs as the mineral barite, which is the main comme ...
, precipitated calcium carbonate, and synthetic pyrogenic silicas.
Hiding pigments, in making paint opaque, also protect the substrate from the harmful effects of ultraviolet light
Ultraviolet (UV) is a form of electromagnetic radiation with wavelength from 10 nm (with a corresponding frequency around 30 PHz) to 400 nm (750 THz), shorter than that of visible light, but longer than X-rays. UV radiation i ...
. Hiding pigments include titanium dioxide
Titanium dioxide, also known as titanium(IV) oxide or titania , is the inorganic compound with the chemical formula . When used as a pigment, it is called titanium white, Pigment White 6 (PW6), or CI 77891. It is a white solid that is insolubl ...
, phthalo blue
Copper phthalocyanine (CuPc), also called phthalocyanine blue, phthalo blue and many other names, is a bright, crystalline, synthetic blue pigment from the group of phthalocyanine dyes. Its brilliant blue is frequently used in paints and dyes. ...
, red iron oxide
Iron(III) oxide or ferric oxide is the inorganic compound with the formula Fe2O3. It is one of the three main oxides of iron, the other two being iron(II) oxide (FeO), which is rare; and iron(II,III) oxide (Fe3O4), which also occurs naturall ...
, and many others.
Fillers are a special type of pigment that serve to thicken the film, support its structure and increase the volume of the paint. Fillers are usually cheap and inert materials, such as diatomaceous earth
Diatomaceous earth (), diatomite (), or kieselgur/kieselguhr is a naturally occurring, soft, siliceous sedimentary rock that can be crumbled into a fine white to off-white powder. It has a particle size ranging from more than 3 μm to le ...
, talc, lime
Lime commonly refers to:
* Lime (fruit), a green citrus fruit
* Lime (material), inorganic materials containing calcium, usually calcium oxide or calcium hydroxide
* Lime (color), a color between yellow and green
Lime may also refer to:
Botany ...
, barytes
Baryte, barite or barytes ( or ) is a mineral consisting of barium sulfate ( Ba S O4). Baryte is generally white or colorless, and is the main source of the element barium. The ''baryte group'' consists of baryte, celestine (strontium sulfate), a ...
, clay, etc. Floor paints that must resist abrasion may contain fine quartz sand as a filler. Not all paints include fillers. On the other hand, some paints contain large proportions of pigment/filler and binder.
Some pigments are toxic, such as the lead
Lead is a chemical element with the symbol Pb (from the Latin ) and atomic number 82. It is a heavy metal that is denser than most common materials. Lead is soft and malleable, and also has a relatively low melting point. When freshly cu ...
pigments that are used in lead paint
Lead paint or lead-based paint is paint containing lead. As pigment, lead(II) chromate (, "chrome yellow"), lead(II,IV) oxide, (, "red lead"), and lead(II) carbonate (, "white lead") are the most common forms.. Lead is added to paint to acceler ...
. Paint manufacturers began replacing white lead pigments with titanium white (titanium dioxide), before lead was banned in paint for residential use in 1978 by the US Consumer Product Safety Commission. The titanium dioxide used in most paints today is often coated with silica/alumina/zirconium for various reasons, such as better exterior durability, or better hiding performance (opacity) promoted by more optimal spacing within the paint film.
Micaceous iron oxide
Iron oxides are chemical compounds composed of iron and oxygen. Several iron oxides are recognized. All are black magnetic solids. Often they are non-stoichiometric. Oxyhydroxides are a related class of compounds, perhaps the best known of whic ...
(MIO) is another alternative to lead for protection of steel, giving more protection against water and light damage than most paints. When MIO pigments are ground into fine particles, most cleave into shiny layers, which reflect light, thus minimising UV degradation and protecting the resin
In polymer chemistry and materials science, resin is a solid or highly viscous substance of plant or synthetic origin that is typically convertible into polymers. Resins are usually mixtures of organic compounds. This article focuses on natu ...
binder. Most pigments used in paint tend to be spherical, but lamellar pigments, such as glass flake and MIO have overlapping plates, which impede the path of water molecules. For optimum performance MIO should have a high content of thin flake-like particles resembling mica
Micas ( ) are a group of silicate minerals whose outstanding physical characteristic is that individual mica crystals can easily be split into extremely thin elastic plates. This characteristic is described as perfect basal cleavage. Mica is ...
. ISO
ISO is the most common abbreviation for the International Organization for Standardization.
ISO or Iso may also refer to: Business and finance
* Iso (supermarket), a chain of Danish supermarkets incorporated into the SuperBest chain in 2007
* Iso ...
10601 sets two levels of MIO content. MIO is often derived from a form of hematite
Hematite (), also spelled as haematite, is a common iron oxide compound with the formula, Fe2O3 and is widely found in rocks and soils. Hematite crystals belong to the rhombohedral lattice system which is designated the alpha polymorph of . ...
.
Additives
Besides the three main categories of ingredients, paint can have a wide variety of miscellaneous additives, which are usually added in small amounts, yet provide a significant effect on the product. Some examples include additives to modify surface tension
Surface tension is the tendency of liquid surfaces at rest to shrink into the minimum surface area possible. Surface tension is what allows objects with a higher density than water such as razor blades and insects (e.g. water striders) to f ...
, improve flow properties, improve the finished appearance, increase wet edge, improve pigment stability, impart antifreeze properties, control foaming, control skinning, etc. Other types of additives include catalyst
Catalysis () is the process of increasing the rate of a chemical reaction by adding a substance known as a catalyst (). Catalysts are not consumed in the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recyc ...
s, thickeners, stabilizers, emulsifier
An emulsion is a mixture of two or more liquids that are normally immiscible (unmixable or unblendable) owing to liquid-liquid phase separation. Emulsions are part of a more general class of two-phase systems of matter called colloids. Altho ...
s, texturizers, adhesion promoters, UV stabilizers, flatteners (de-glossing agents), biocides to fight bacteria
Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were among ...
l growth and the like.
Additives normally do not significantly alter the percentages of individual components in a formulation.
Color changing
Various technologies exist for making paints that change color. Thermochromic ink Thermochromic ink (also called thermochromatic ink) is a type of dye that changes color when temperatures increase or decrease. Often used in the manufacture of many toys or product packaging, as well as thermometers. Thermochromic ink can also turn ...
and coatings contain materials that change conformation when heat is applied or removed, and so they change color. Liquid crystal
Liquid crystal (LC) is a state of matter whose properties are between those of conventional liquids and those of solid crystals. For example, a liquid crystal may flow like a liquid, but its molecules may be oriented in a crystal-like way. T ...
s have been used in such paints, such as in the thermometer strips and tapes used in aquaria and novelty/promotional thermal cups and straws.
Photochromic materials are used to make eyeglasses and other products. Similar to thermochromic molecules, photochromic molecules change conformation when light energy is applied or removed, and so they change color.
Color-changing paints can also be made by adding halochromic compounds or other organic pigments. One patent cites use of these indicators for wall coating applications for light-colored paints. When the paint is wet it is pink in color but upon drying it regains its original white color. As cited in patent, this property of the paint enabled two or more coats to be applied on a wall properly and evenly. The previous coats having dried would be white whereas the new wet coat would be distinctly pink. Ashland Inc. introduced foundry refractory coatings with similar principle in 2005 for use in foundries.
Electrochromic paints change color in response to an applied electric current. Car manufacturer Nissan
, trade name, trading as Nissan Motor Corporation and often shortened to Nissan, is a Japanese multinational corporation, multinational Automotive industry, automobile manufacturer headquartered in Nishi-ku, Yokohama, Japan. The company sells ...
has been reportedly working on an electrochromic paint, based on particles of paramagnetic iron oxide
Iron oxides are chemical compounds composed of iron and oxygen. Several iron oxides are recognized. All are black magnetic solids. Often they are non-stoichiometric. Oxyhydroxides are a related class of compounds, perhaps the best known of whic ...
. When subjected to an electromagnetic field the paramagnetic particles change spacing, modifying their color and reflective properties. The electromagnetic field would be formed using the conductive metal of the car body. Electrochromic paints can be applied to plastic substrates as well, using a different coating chemistry. The technology involves using special dyes that change conformation when an electric current is applied across the film itself. This new technology has been used to achieve glare protection at the touch of a button in passenger airplane windows.
Color can also change depending on viewing angle, using iridescence
Iridescence (also known as goniochromism) is the phenomenon of certain surfaces that appear to gradually change color as the angle of view or the angle of illumination changes. Examples of iridescence include soap bubbles, feathers, butterfl ...
, for example, in ChromaFlair
ChromaFlair is a pigment used in paint systems, primarily for automobiles. When the paint is applied, it changes color depending on the light source and viewing angle. It was created at JDS Uniphase and is used by DuPont and PPG.
Names
The pai ...
.
Art
Since the time of the Renaissance
The Renaissance ( , ) , from , with the same meanings. is a period in European history marking the transition from the Middle Ages to modernity and covering the 15th and 16th centuries, characterized by an effort to revive and surpass ideas ...
, siccative An oil drying agent, also known as siccative, is a coordination compound that accelerates ( catalyzes) the hardening of drying oils, often as they are used in oil-based paints. This so-called "drying" (actually a chemical reaction that produces an ...
(drying) oil paints, primarily linseed oil
Linseed oil, also known as flaxseed oil or flax oil (in its edible form), is a colourless to yellowish oil obtained from the dried, ripened seeds of the flax plant (''Linum usitatissimum''). The oil is obtained by pressing, sometimes followed by ...
, have been the most commonly used kind of paints in fine art applications; oil paint
Oil paint is a type of slow-drying paint that consists of particles of pigment suspended in a drying oil, commonly linseed oil. The viscosity of the paint may be modified by the addition of a solvent such as turpentine or white spirit, and varn ...
is still common today. However, in the 20th century, new water-based paints such acrylic paint
Acrylic paint is a fast-drying paint made of pigment suspended in acrylic polymer emulsion and plasticizers, silicone oils, defoamers, stabilizers, or metal soaps. Most acrylic paints are water-based, but become water-resistant when dry. Depe ...
s, entered the market with the development of acrylic
Acrylic may refer to:
Chemicals and materials
* Acrylic acid, the simplest acrylic compound
* Acrylate polymer, a group of polymers (plastics) noted for transparency and elasticity
* Acrylic resin, a group of related thermoplastic or thermosett ...
and other latex paints. Milk paint
Milk paint is a nontoxic milk-based paint. It can be made from milk and lime, generally with pigments added for color. In other recipes, borax is mixed with milk's casein protein in order to activate the casein and as a preservative.
Milk paint ...
s (also called casein
Casein ( , from Latin ''caseus'' "cheese") is a family of related phosphoproteins (CSN1S1, αS1, aS2, CSN2, β, K-casein, κ) that are commonly found in mammalian milk, comprising about 80% of the proteins in cow's milk and between 20% and 60% of ...
), where the medium is derived from the natural emulsion that is milk
Milk is a white liquid food produced by the mammary glands of mammals. It is the primary source of nutrition for young mammals (including breastfed human infants) before they are able to digestion, digest solid food. Immune factors and immune ...
, were common in the 19th century and are still used. Used by the earliest western artists, Egg tempera
Tempera (), also known as egg tempera, is a permanent, fast-drying painting medium consisting of colored pigments mixed with a water-soluble binder medium, usually glutinous material such as egg yolk. Tempera also refers to the paintings done ...
(where the medium is an emulsion
An emulsion is a mixture of two or more liquids that are normally immiscible (unmixable or unblendable) owing to liquid-liquid phase separation. Emulsions are part of a more general class of two-phase systems of matter called colloids. Althoug ...
of raw egg yolk
Among animals which produce eggs, the yolk (; also known as the vitellus) is the nutrient-bearing portion of the egg whose primary function is to supply food for the development of the embryo. Some types of egg contain no yolk, for example bec ...
mixed with oil) remains in use as well, as are encaustic wax
Waxes are a diverse class of organic compounds that are lipophilic, malleable solids near ambient temperatures. They include higher alkanes and lipids, typically with melting points above about 40 °C (104 °F), melting to give low ...
-based paints. Gouache
Gouache (; ), body color, or opaque watercolor is a water-medium paint consisting of natural pigment, water, a binding agent (usually gum arabic or dextrin), and sometimes additional inert material. Gouache is designed to be opaque. Gouache h ...
is an opaque variant of watercolor
Watercolor (American English) or watercolour (British English; see spelling differences), also ''aquarelle'' (; from Italian diminutive of Latin ''aqua'' "water"), is a painting method”Watercolor may be as old as art itself, going back to t ...
, which is based around varying levels of translucency; both paints use gum arabic as the carrier and water as a thinner. Gouache is also known as 'designer color' or 'body color'.
Poster paint Poster paint (also known as tempera paint in the US) is a distemper paint that usually uses Starch, Cornstarch, cellulose, gum-water or another glue size as its binder. It either comes in large bottles or jars or in a powdered form. It is normally ...
is a distemper
Distemper may refer to:
Illness
*A viral infection
**Canine distemper, a disease of dogs
**Feline distemper, a disease of cats
** Phocine distemper, a disease of seals
*A bacterial infection
**Equine distemper, or Strangles, a bacterial infectio ...
paint that has been used primarily in the creation of student works, or by children. There are varying brands of poster paint and depending on the brand, the quality will differ. More inexpensive brands will often crack or fade over time if they are left on a poster for an extended time.
Application
Paint can be applied as a solid, a gaseous suspension (aerosol
An aerosol is a suspension (chemistry), suspension of fine solid particles or liquid Drop (liquid), droplets in air or another gas. Aerosols can be natural or Human impact on the environment, anthropogenic. Examples of natural aerosols are fog o ...
) or a liquid. Techniques vary depending on the practical or artistic results desired.
As a solid (usually used in industrial and automotive applications), the paint is applied as a very fine powder, then baked at high temperature. This melts the powder and causes it to adhere to the surface. The reasons for doing this involve the chemistries of the paint, the surface itself, and perhaps even the chemistry of the substrate (the object being painted). This is called " powder coating" an object.
As a gas or as a gaseous suspension, the paint is suspended in solid or liquid form in a gas that is sprayed on an object. The paint sticks to the object. This is called "spray painting" an object. The reasons for doing this include:
* The application mechanism is air and thus no solid object touches the object being painted;
* The distribution of the paint is uniform, so there are no sharp lines;
* It is possible to deliver very small amounts of paint;
*Painting multiple items at once quickly and efficiently;
* A chemical (typically a solvent
A solvent (s) (from the Latin '' solvō'', "loosen, untie, solve") is a substance that dissolves a solute, resulting in a solution. A solvent is usually a liquid but can also be a solid, a gas, or a supercritical fluid. Water is a solvent for ...
) can be sprayed along with the paint to dissolve together both the delivered paint and the chemicals on the surface of the object being painted;
* Some chemical reactions in paint involve the orientation of the paint molecules
A molecule is a group of two or more atoms held together by attractive forces known as chemical bonds; depending on context, the term may or may not include ions which satisfy this criterion. In quantum physics, organic chemistry, and bioche ...
.
* Expression
In the liquid application, paint can be applied by direct application using brush
A brush is a common tool with bristles, wire or other filaments. It generally consists of a handle or block to which filaments are affixed in either a parallel or perpendicular orientation, depending on the way the brush is to be gripped durin ...
es, paint rollers, blades
A blade is the portion of a tool, weapon, or machine with an edge that is designed to puncture, chop, slice or scrape surfaces or materials. Blades are typically made from materials that are harder than those they are to be used on. Historic ...
, scrapers, other instruments, or body parts such as fingers and thumbs.
Rollers generally have a handle that allows for different lengths of poles to be attached, allowing painting at different heights. Generally, roller application requires two coats for an even color. A roller with a thicker nap
A nap is a short period of sleep, typically taken during daytime hours as an adjunct to the usual nocturnal sleep period. Naps are most often taken as a response to drowsiness during waking hours. A nap is a form of biphasic or polyphasic sl ...
is used to apply paint on uneven surfaces. Edges are often finished with an angled brush.
*Using the finish flat one would most likely use a 1/2" nap roller
*Using the finish eggshell one would most likely use a 3/8" nap roller
*Using the finish satin or pearl one would most likely use a 3/8" nap roller
*Using the finish semi-gloss or gloss one would most likely use a 3/16" nap roller
After liquid paint is applied, there is an interval during which it can be blended with additional painted regions (at the "wet edge") called "open time". The open time of an oil or alkyd-based emulsion paint can be extended by adding white spirit
White spirit (AU, UK & Ireland)Primarily in the United Kingdom and Australia. In New Zealand "white spirit" can also refer to Coleman fuel (white gas). or mineral spirits (US, Canada), also known as mineral turpentine (AU/NZ), turpentine substitu ...
, similar glycols such as Dowanol (propylene glycol ether) or open time prolongers. This can also facilitate the mixing of different wet paint layers for aesthetic effect. Latex and acrylic emulsions require the use of drying retardants suitable for water-based coatings. Depending on the quality and type of liquid paint used, the open time will vary. Oil paints for instance are renowned for their open time as oil paints allow for artists to blend the colors for extended periods of time without having to add any extending agents.
Paint application by spray is the most popular method in industry. In this, paint is aerosolized by the force of compressed air or by the action of high-pressure compression of the paint itself, and the paint is turned into small droplets that travel to the article to be painted. Alternate methods are airless spray, hot spray, hot airless spray, and any of these with an electrostatic spray included. There are numerous electrostatic methods available.
Dipping used to be the norm for objects such as filing cabinets, but this has been replaced by high-speed air turbine-driven bells with electrostatic spray. Car bodies are primed using cathodic elephoretic primer, which is applied by charging the body depositing a layer of primer. The unchanged residue is rinsed off and the primer stoved.
Many paints tend to separate when stored, the heavier components settling to the bottom, and require mixing before use. Some paint outlets have machines for mixing the paint by shaking the can vigorously for a few minutes.
The opacity and the film thickness of paint may be measured using a drawdown card
Drawdown cards are used for testing paints and coating
A coating is a covering that is applied to the surface of an object, usually referred to as the substrate. The purpose of applying the coating may be decorative, functional, or both. Coati ...
.
Water-based paints tend to be the easiest to clean up after use; the brushes and rollers can be cleaned with soap and water.
Proper disposal of left over paint is a challenge. Sometimes it can be recycled: Old paint may be usable for a primer coat or an intermediate coat, and paints of similar chemistry can be mixed to make a larger amount of a uniform color.
To dispose of paint it can be dried and disposed of in the domestic waste stream, provided that it contains no prohibited substances (see container). Disposal of liquid paint usually requires special handling and should be treated as hazardous waste, and disposed of according to local regulations.
Product variants
*Primer
Primer may refer to:
Arts, entertainment, and media Films
* ''Primer'' (film), a 2004 feature film written and directed by Shane Carruth
* ''Primer'' (video), a documentary about the funk band Living Colour
Literature
* Primer (textbook), a t ...
is a preparatory coating put on materials before applying the paint itself. The primed surface ensures better adhesion
Adhesion is the tendency of dissimilar particles or surfaces to cling to one another ( cohesion refers to the tendency of similar or identical particles/surfaces to cling to one another).
The forces that cause adhesion and cohesion can be ...
of the paint, thereby increasing the durability of the paint and providing improved protection for the painted surface. Suitable primers also may block and seal stains, or hide a color that is to be painted over.
*Emulsion
An emulsion is a mixture of two or more liquids that are normally immiscible (unmixable or unblendable) owing to liquid-liquid phase separation. Emulsions are part of a more general class of two-phase systems of matter called colloids. Althoug ...
paints are water-based paints in which the paint material is dispersed in a liquid that consists mainly of water. For suitable purposes this has advantages in fast-drying, low toxicity, low cost, easier application, and easier cleaning of equipment, among other factors.
*Varnish
Varnish is a clear transparent hard protective coating or film. It is not a stain. It usually has a yellowish shade from the manufacturing process and materials used, but it may also be pigmented as desired, and is sold commercially in various ...
and shellac are in effect paints without pigment; they provide a protective coating without substantially changing the color of the surface, though they can emphasise the colour of the material.
* Wood stain is a type of paint that is formulated to be very "thin", meaning low in viscosity, so that the pigment soaks into a material such as wood rather than remaining in a film on the surface. Stain is mainly dispersed pigment
A pigment is a colored material that is completely or nearly insoluble in water. In contrast, dyes are typically soluble, at least at some stage in their use. Generally dyes are often organic compounds whereas pigments are often inorganic compo ...
or dissolved dye
A dye is a colored substance that chemically bonds to the substrate to which it is being applied. This distinguishes dyes from pigments which do not chemically bind to the material they color. Dye is generally applied in an aqueous solution an ...
plus binder material in a solvent. It is designed to add color without providing a surface coating.
*Lacquer
Lacquer is a type of hard and usually shiny coating or finish applied to materials such as wood or metal. It is most often made from resin extracted from trees and waxes and has been in use since antiquity.
Asian lacquerware, which may be ca ...
is a solvent-based paint or varnish that produces an especially hard, durable finish. Usually it is a rapidly drying formulation.
*Enamel paint
Enamel paint is paint that air-dries to a hard, usually glossy, finish, used for coating surfaces that are outdoors or otherwise subject to hard wear or variations in temperature; it should not be confused with decorated objects in "painted ename ...
is formulated to give an especially hard, usually glossy, finish. Some enamel paints contain fine glass powder or metal flake instead of the color pigments in standard oil-based paints. Enamel paint sometimes is mixed with varnish or urethane to improve its shine and hardness.
*A glaze is an additive used with paint to slow drying time and increase translucency, as in faux painting
Faux painting or faux finishing are terms used to describe decorative paint finishes that replicate the appearance of materials such as marble, wood or stone. The term comes from the French word ''faux'', meaning false, as these techniques start ...
and for some artistic effects.
*A roof coating
A roof coating is a monolithic, fully adhered, fluid applied roofing membrane. Many roof coatings are elastomeric, that is, they have elastic properties that allow them to stretch and return to their original shape without damage.
Typical roof coa ...
is a fluid that sets as an elastic membrane that can stretch without harm. It provides UV protection to polyurethane foam and is widely used in roof restoration.
* Fingerpaints are formulations suitable for application with the fingers; they are popular for use by children in primary school activities.
*Ink
Ink is a gel, sol, or solution that contains at least one colorant, such as a dye or pigment, and is used to color a surface to produce an image, text, or design. Ink is used for drawing or writing with a pen, brush, reed pen, or quill. Thi ...
s are similar to paints, except that they are typically made using finely ground pigments or dyes, and are not designed to leave a thick film of binder. They are used largely for writing, printing, or calligraphy
Calligraphy (from el, link=y, καλλιγραφία) is a visual art related to writing. It is the design and execution of lettering with a pen, ink brush, or other writing instrument. Contemporary calligraphic practice can be defined as "t ...
.
* Anti-graffiti coatings are used to defeat the marking of surfaces by graffiti
Graffiti (plural; singular ''graffiti'' or ''graffito'', the latter rarely used except in archeology) is art that is written, painted or drawn on a wall or other surface, usually without permission and within public view. Graffiti ranges from s ...
artists or vandals. There are two categories of anti-graffiti coatings: sacrificial and non-bonding:
:*Sacrificial coatings are clear coatings that allow the removal of graffiti, usually by washing the surface with high-pressure water that removes the graffiti together with the coating (hence the term "sacrificial"). After removal of the graffiti, the sacrificial coating must be re-applied for continued protection. Such sacrificial protective coatings are most commonly used on natural-looking masonry surfaces, such as statuary and marble walls, and on rougher surfaces that are difficult to clean.
:*Non-bonding coatings are clear, high-performance coatings, usually catalyzed polyurethanes
Polyurethane (; often abbreviated PUR and PU) refers to a class of polymers composed of organic units joined by carbamate (urethane) links. In contrast to other common polymers such as polyethylene and polystyrene, polyurethane is produced fro ...
, that do not bond strongly to paints used for graffiti. Graffiti on such a surface can be removed with a solvent wash, without damaging either the underlying surface or the protective non-bonding coating. These coatings work best on smooth surfaces, and are especially useful on decorative surfaces such as mosaics or painted murals, which might be expected to suffer harm from high pressure sprays.
*Urine-repellent paint is a very hydrophobic
In chemistry, hydrophobicity is the physical property of a molecule that is seemingly repelled from a mass of water (known as a hydrophobe). In contrast, hydrophiles are attracted to water.
Hydrophobic molecules tend to be nonpolar and, th ...
(water-repellent) paint. It has been used by cities and other property owners to deter men from urinating against walls, as the urine splashes back on their shoes, instead of dripping down the wall.
*Anti-climb paint
Anti-climb paint (also known as non-drying paint, anti-intruder paint, anti-vandal grease) is a class of paint consisting of a thick oily coating that is applied with a stiff brush, trowel or by hand using a protective glove. In appearance it is ...
is a non-drying paint that appears normal but is extremely slippery. It is useful on drainpipes and ledges to deter burglars and vandals from climbing them, and is found in many public places. When a person attempts to climb objects coated with the paint, it rubs off onto the climber, as well as making it hard for them to climb.
* Anti-fouling paint, or bottom paint, prevents barnacles and other marine organisms from adhering to the hulls of ships.
* Insulative paint or insulating paint, reduces the rate of thermal transfer through a surface it's applied to. One type of formulation is based on the addition of hollow microspheres
Microparticles are particles between 0.1 and 100 μm in size. Commercially available microparticles are available in a wide variety of materials, including ceramics, glass, polymers, and metals. Microparticles encountered in daily life includ ...
to any suitable type of paint.
*Anti-slip paint contains chemicals or grit to increase the friction of a surface so as to decrease the risk of slipping, particularly in wet conditions.
* Road marking paint is specially used to marking and painting road traffic signs and lines, to form a durable coating film on the road surface. It must be fast-drying, provide a thick coating, and resist wear and slipping, especially in wet conditions.
*Luminous paint
Luminous paint or luminescent paint is paint that exhibits luminescence. In other words, it gives off Visible spectrum, visible light through fluorescence, phosphorescence, or radioluminescence. There are three types of luminous paints: fluoresc ...
or luminescent paint is paint that exhibits luminescence. In other words, it gives off visible light through fluorescence, phosphorescence, or radioluminescence.
*Chalk paint
Chalk paint is a water-based, decorative paint invented by Annie Sloan which may be applied over almost any surface. It requires very little preparation and needs a topcoat to avoid flaking. Chalk paints are also used by utility companies to ma ...
is a decorative paint used for home decor to achieve looks such as shabby chic
Shabby chic is a style of interior design where furniture and furnishings are either chosen for their appearance of age and signs of wear and tear or where new items are distressing, distressed to achieve the appearance of an antique. At the sa ...
or vintage
Vintage, in winemaking, is the process of picking grapes and creating the finished product—wine (see Harvest (wine)). A vintage wine is one made from grapes that were all, or primarily, grown and harvested in a single specified year. In certa ...
with home decor
Interior design is the art and science of enhancing the interior of a building to achieve a healthier and more aesthetically pleasing environment for the people using the space. An interior designer is someone who plans, researches, coordina ...
.
Finish types
*Flat Finish paint is generally used on ceilings or walls that are in bad shape. This finish is useful for hiding imperfections in walls and it is economical in effectively covering relatively great areas. However, this finish is not easily washable and is subject to staining.
*Matte Finish is generally similar to flat finish, but such paints commonly offer superior washability and coverage. (See Gloss and matte paint
Sheen is a measure of the reflected light ( glossiness) from a paint finish. ''Glossy'' and ''flat'' (or ''matte'') are typical extreme levels of glossiness of a finish. Glossy paints are shiny and reflect most light in the specular (mirror-lik ...
.)
* Eggshell Finish has some sheen, supposedly like that of the shell on an egg. This finish provides great washability, but is not very effective at hiding imperfections on walls and similar surfaces. Eggshell finish is valued for bathrooms because it is washable and water repellent, so that it tends not to peel in a wet environment.
*Pearl (Satin) Finish is very durable in terms of washability and resistance to moisture, even in comparison to an eggshell finish. It protects walls from dirt, moisture, and stains. Accordingly, it is exceptionally valuable for bathrooms, furniture, and kitchens, but it is shinier than eggshell, so it is even more prone to show imperfections.
*Semi-Gloss Finish typically is used on the trim to emphasize detail and elegance, and to show off woodwork, such as on doors and furniture. It provides a shiny surface and provides good protection from moisture and stains on walls. Its gloss does however emphasize imperfections on the walls and similar surfaces. It is popular in schools and factories where washability and durability are the main considerations.
*High-gloss paint is a highly glossy and super shiny form of paint that is light reflecting and has a mirror-like look. It pairs well with other finishes. While it is highly durable and easy to clean, high gloss paint is known for obvious visibility of imperfections like scratches, dents.
Failure
The main reasons for paint failure after application on the surface are the applicator and improper treatment of the surface.
Defects or degradation can be attributed to:
; Dilution
:This usually occurs when the dilution of the paint is not done as per manufacturers recommendation. There can be a case of over dilution and under dilution, as well as dilution with the incorrect diluent.
; Contamination
: Foreign contaminants added without the manufacturers' consent can cause various film defects.
; Peeling/Blistering
: Most commonly due to improper surface treatment before application and inherent moisture/dampness being present in the substrate. The degree of blistering can be assessed according to ISO 4628 Part 2 or ASTM Method D714 (Standard Test Method for Evaluating Degree of Blistering of Paints).
; Chalking
: Chalking is the progressive powdering of the paint film on the painted surface. The primary reason for the problem is polymer degradation of the paint matrix due to exposure of UV radiation
Ultraviolet (UV) is a form of electromagnetic radiation with wavelength from 10 nm (with a corresponding frequency around 30 PHz) to 400 nm (750 THz), shorter than that of visible light, but longer than X-rays. UV radiation i ...
in sunshine
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 th ...
and condensation from dew. The degree of chalking varies as epoxies react quickly while acrylics and polyurethanes can remain unchanged for long periods. The degree of chalking can be assessed according to International Standard
international standard is a technical standard developed by one or more international standards organizations. International standards are available for consideration and use worldwide. The most prominent such organization is the International Or ...
ISO 4628 Part 6 or 7 or American Society of Testing and Materials
ASTM International, formerly known as American Society for Testing and Materials, is an international standards organization that develops and publishes voluntary consensus technical standards for a wide range of materials, products, systems, an ...
(ASTM) Method D4214 (Standard Test Methods for Evaluating the Degree of Chalking of Exterior Paint Films).
; Cracking
: Cracking of paint film is due to the unequal expansion or contraction of paint coats. It usually happens when the coats of the paint are not allowed to cure/dry completely before the next coat is applied. The degree of cracking can be assessed according to International Standard ISO 4628 Part 4 or ASTM Method D661 (Standard Test Method for Evaluating Degree of Cracking of Exterior Paints). Cracking can also occur when the paint is applied to a surface that is incompatible or unstable. For instance, clay that hasn't dried completely when painted will cause the paint to crack due to the residual moisture in the clay.
;Erosion
:Erosion is very quick chalking. It occurs due to external agents like air, water etc. It can be evaluated using ASTM Method ASTM D662 (Standard Test Method for Evaluating Degree of Erosion of Exterior Paints). The generation of acid by fungal species can be a significant component of erosion of painted surfaces. The fungus '' Aureobasidium pullulans'' is known for damaging wall paints.
File:Love by SillyPuttyEnemies.jpg, Peeling
File:Paint chalking.jpg, Polyurethane paint progressively chalking
File:Peeling paint (pink).jpg, Cracking
Dangers
Volatile organic compound
Volatile organic compounds (VOCs) are organic compounds that have a high vapour pressure at room temperature. High vapor pressure correlates with a low boiling point, which relates to the number of the sample's molecules in the surrounding air, a ...
s (VOCs) in paint are considered harmful to the environment and especially for people who work with them on a regular basis. Exposure to VOCs has been related to organic solvent syndrome, although this relation has been somewhat controversial. The controversial solvent 2-butoxyethanol
2-Butoxyethanol is an organic compound with the chemical formula BuOC2H4OH (Bu = CH3CH2CH2CH2). This colorless liquid has a sweet, ether-like odor, as it derives from the family of glycol ethers, and is a butyl ether of ethylene glycol. As a rela ...
is also used in paint production. Jurisdictions such as Canada
Canada is a country in North America. Its ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, covering over , making it the world's second-largest country by tot ...
, China
China, officially the People's Republic of China (PRC), is a country in East Asia. It is the world's most populous country, with a population exceeding 1.4 billion, slightly ahead of India. China spans the equivalent of five time zones and ...
, the EU, India
India, officially the Republic of India (Hindi: ), is a country in South Asia. It is the seventh-largest country by area, the second-most populous country, and the most populous democracy in the world. Bounded by the Indian Ocean on the so ...
, the United States, and South Korea have definitions for VOCs in place, along with regulations to limit the use of VOCs in consumer products such as paint.
In the US, environmental regulations, consumer demand, and advances in technology led to the development of low-VOC and zero-VOC paints and finishes. These new paints are widely available and meet or exceed the old high-VOC products in performance and cost-effectiveness while having significantly less impact on human and environmental health.
Globally, the most widely accepted standard for acceptable levels of VOC in paint i
Green Seal’s GS-11 Standards
from the US which defines different VOC levels acceptable for different types of paint based on use case and performance requirements.
A polychlorinated biphenyl (PCB) was reported (published in 2009) in air samples collected in Chicago, Philadelphia, the Arctic, and several sites around the Great Lakes. PCB is a global pollutant and was measured in the wastewater effluent from paint production. The widespread distribution of PCB suggests volatilization of this compound from surfaces, roofs etc. PCB is present in consumer goods including newspapers, magazines, and cardboard boxes, which usually contain color pigments. Therefore, a hypothesis exists that PCB congeners are present as byproduct in some current commercial pigments.
See also
* Adhesive
Adhesive, also known as glue, cement, mucilage, or paste, is any non-metallic substance applied to one or both surfaces of two separate items that binds them together and resists their separation.
The use of adhesives offers certain advant ...
* Aerosol paint
* Anti-graffiti coating
* Bresle method
The Bresle method is used to determine concentration of soluble salts on metal surfaces prior to coating application, such as painting. These salts can cause serious adhesion problems after time.
Importance
Salt is in coastal areas. It can be ta ...
* Brush
A brush is a common tool with bristles, wire or other filaments. It generally consists of a handle or block to which filaments are affixed in either a parallel or perpendicular orientation, depending on the way the brush is to be gripped durin ...
* Coating
A coating is a covering that is applied to the surface of an object, usually referred to as the Substrate (materials science), substrate. The purpose of applying the coating may be decorative, functional, or both. Coatings may be applied as liquid ...
* Computer graphics
Computer graphics deals with generating images with the aid of computers. Today, computer graphics is a core technology in digital photography, film, video games, cell phone and computer displays, and many specialized applications. A great de ...
* Distressing
* Environmental issues with paint
The environmental effects of paint can vary depending on the type of paint used and mitigation measures. Traditional painting materials and processes can have harmful effects on the environment, including those from the use of lead and other addi ...
* Faux painting
Faux painting or faux finishing are terms used to describe decorative paint finishes that replicate the appearance of materials such as marble, wood or stone. The term comes from the French word ''faux'', meaning false, as these techniques start ...
* Painting
Painting is the practice of applying paint, pigment, color or other medium to a solid surface (called the "matrix" or "support"). The medium is commonly applied to the base with a brush, but other implements, such as knives, sponges, and ...
* Formulations
* Fresco
Fresco (plural ''frescos'' or ''frescoes'') is a technique of mural painting executed upon freshly laid ("wet") lime plaster. Water is used as the vehicle for the dry-powder pigment to merge with the plaster, and with the setting of the plaste ...
* Gloss and matte paint
Sheen is a measure of the reflected light ( glossiness) from a paint finish. ''Glossy'' and ''flat'' (or ''matte'') are typical extreme levels of glossiness of a finish. Glossy paints are shiny and reflect most light in the specular (mirror-lik ...
* Interior radiation control coating Interior Radiation Control Coating Systems (IRCCS), sometimes referred to as radiant barrier coatings, are paints designed to provide thermal insulation to buildings.
Standards
The American Society for Testing and Materials (ASTM) and the Reflect ...
* Lacquer
Lacquer is a type of hard and usually shiny coating or finish applied to materials such as wood or metal. It is most often made from resin extracted from trees and waxes and has been in use since antiquity.
Asian lacquerware, which may be ca ...
* List of art media
Arts media is the material and tools used by an artist, composer or designer to create a work of art, for example, "pen and ink" where the pen is the tool and the ink is the material. Here is a list of types of art and the media used within those ...
* NACE International
* Paint adhesion testing
In the paint and coating industries, paint adhesion testing is often used to determine if the paint or coating will adhere properly to the substrates to which they are applied. There are several different tests to measure the resistance of paints ...
* Paint recycling
Paint is a recyclable item. Latex paint is collected at collection facilities in many countries and shipped to paint-recycling facilities.
How paint is recycled
There are many ways that paint can be recycled. Most often, the highest quality ...
* Paint (software)
* Paint stripper
* Powder coating
* Primer
Primer may refer to:
Arts, entertainment, and media Films
* ''Primer'' (film), a 2004 feature film written and directed by Shane Carruth
* ''Primer'' (video), a documentary about the funk band Living Colour
Literature
* Primer (textbook), a t ...
* Road surface marking
* Roof coating
A roof coating is a monolithic, fully adhered, fluid applied roofing membrane. Many roof coatings are elastomeric, that is, they have elastic properties that allow them to stretch and return to their original shape without damage.
Typical roof coa ...
* Soy paint
Soy paint is paint made primarily from soy, it combines the advantage of being a renewable resource with the potential of non-toxic product.
Oil
Soy oils have been used in paint since at least the early 1900s, with paint being the second largest ...
* Stain-blocking primer
Stain-blocking primers are used to cover stains such as watermarks, nicotine (actually tar), markers, smoke, and prevent them bleeding through newly applied layers of paint. They also provide adhesion over problematic surfaces, giving better film ...
References
Further reading
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