Editing Paint (section)

===Pigment, dye and filler===
{{main|Pigment}}
Pigments are solid particles or flakes incorporated in the paint, usually to contribute color to the paint film. Pigments impart color by selective absorption of certain wavelengths of light and/or by scattering or reflecting light. The particle size of the pigment is critical to the light-scattering mechanism. The size of such particles can be measured with a [[Hegman gauge]]. Dyes, on the other hand, are dissolve in the paint and impart color only by the selective absorption mechanism.<ref>{{Cite web|url=https://colour-index.com/definitions-of-a-dye-and-a-pigment|title=Definitions of a Dye and a Pigment |date=April 26, 2024 }}</ref> Paints can be formulated with only pigments, only dyes, both, or neither.

Pigments can also be used to give the paint special physical or optical properties, as opposed to imparting color, in which case they are called functional pigments.<ref>{{Cite web|url=https://www.ulprospector.com/knowledge/4751/pc-four-important-functional-pigments/#:~:text=Functional%20Pigments%20(FP)%20is%20a,types%2C%20but%20there%20are%20others.|title=Four Important Functional Pigments|date=April 26, 2024 }}</ref> Fillers or extenders are an important class of the functional pigments. These are typically used to build film thickness and/or reduce the cost of the paint, or they can impart toughness and texture to the film.<ref>{{Cite book|url=https://books.google.com/books?id=KfggDAAAQBAJ&q=Pigments+are+granular+solids+incorporated+in+the+paint+to+contribute+color&pg=PA59|title=Dyes and Pigments|last1=Gürses|first1=Ahmet|last2=Açıkyıldız|first2=Metin|last3=Güneş|first3=Kübra|last4=Gürses|first4=M. Sadi|date=2016-05-04|publisher=Springer|isbn=9783319338927|language=en}}</ref> Fillers are usually cheap and inert materials, such as [[diatomaceous earth]], [[talc]], [[lime (mineral)|lime]], [[barytes]], clay, etc. Floor paints that must resist abrasion may contain fine quartz sand as a filler. 

Sometimes, a single pigment can serve both decorative and functional purposes. For example some decorative pigments protect the substrate from the harmful effects of [[ultraviolet light]] by making the paint opaque to these wavelengths, i.e. by selectively absorbing them. These hiding pigments include [[titanium dioxide]], [[Phthalocyanine Blue BN|phthalo blue]], [[red iron oxide]], and many others.

Some pigments are toxic, such as the [[lead]] pigments that are used in [[lead paint]]. 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.<ref>{{Cite web|url=https://www.latimes.com/archives/la-xpm-2011-oct-14-la-sci-ancient-paint-20111014-story.html|title=Archives|website=[[Los Angeles Times]]|date=14 October 2011 }}</ref>

Micaceous [[Iron(III) oxide|iron oxide]] (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]] 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.<ref>{{Cite web|url=http://www.duluxprotectivecoatings.com.au/technotespdf/5.2.1%20MIO%20Coatings%20-%20What%20Are%20They.pdf|title=MIO Coatings – What Are They?|date=2009|website=Dulux Protective Coatings}}</ref> For optimum performance MIO should have a high content of thin flake-like particles resembling [[mica]]. [[International Organization for Standardization|ISO]] 10601 sets two levels of MIO content.<ref>{{Cite web|url=https://www.iso.org/obp/ui/#iso:std:38753:en|title=ISO 10601:2007|website=Micaceous iron oxide pigments|publisher=International Organization for Standardization}}</ref> MIO is often derived from a form of [[hematite]].

Pigments can be classified as either natural or synthetic. Natural pigments are taken from the earth or plant sources and include colorants such as metal oxides or carbon black, or various [[clay]]s, [[calcium carbonate]], [[mica]], [[silica]]s, and [[talc]]s. Synthetics include a host of colorants created in the lab as well as engineered molecules, [[calcining|calcined]] clays, [[blanc fixe]], precipitated calcium carbonate, and synthetic pyrogenic silicas. The pigments and dyes that are used as colorants are classified by chemical type using the Color Index system, which is commercially significant.<ref>{{Cite web|url=https://colour-index.com/cicn-groups-sub-groups|title=CICN Groups and Sub-Groups|date=April 26, 2024 }}</ref>