Luminous paint
Encyclopedia
Luminous paint or luminescent paint is paint
that exhibits luminescence
. In other words, it gives off visible
light
through fluorescence
, phosphorescence
, or radioluminescence
.
Fluorescent paint reacts to long-wave ultraviolet
(UV) radiation, commonly known as black light
. Through the mechanism of fluorescence
, UV-sensitive pigment
s present in the paint absorb black light and give off visible light
in return.
There are two basic kinds of fluorescent paint: visible and invisible. Visible fluorescent paint can appear any bright color under white
light, and glows brilliantly under black light. Invisible fluorescent paint appears white or clear under white light, but glows a particular color—depending on the pigment used—under black light.
This type of paint has extensive applications in the entertainment industry, and it can be used to create black light effects such as invisible images, dual images, day–night transitions, and 3-D effects.
paint is commonly called "glow-in-the-dark" paint. It is made from phosphors such as silver-activated zinc sulfide
or, more recently, doped
strontium aluminate
, and typically glows a pale green to greenish blue color. The mechanism for producing light is similar to that of fluorescent paint, but the emission of visible light persists for some time after it has been exposed to light. Phosphorescent paints have a sustained glow which lasts for some minutes or hours after exposure to light, but will eventually fade over time.
This type of paint has been used to mark escape paths in aircraft and for decorative use, such as "stars" applied to walls and ceilings. It is also increasingly used as an alternative to radioluminescent paint. Kenner
's Lightning Bug Glo-Juice was a popular non-toxic paint product in 1968, marketed at children, alongside other glow-in-the-dark toys and novelties.
.
(radionuclide
) combined with a radioluminescent
substance. The isotopes selected are typically strong emitters of fast electron
s (beta radiation
), preferred since this radiation will not penetrate an enclosure. Radioluminescent paints will glow without exposure to light until the radioactive isotope has decayed (or the paint itself degrades), which may be many years. They are therefore sometimes referred to as "self-luminous".
Radioluminescent paint was invented in 1908 and originally incorporated radium
-226. The toxicity of radium was not initially understood, and radium-based paint saw widespread use in, for example, watches and aircraft instruments. During the 1920s and 1930s, the harmful effects of this paint became increasingly clear. A notorious case involved the "Radium Girls
", a group of women who painted watchfaces and later suffered adverse health effects from ingestion. It is now recognised that radium paint requires great care in application, maintenance and disposal to avoid creation of a hazardous condition.
In the second half of the 20th century, radium was progressively replaced by safer radionuclides such as promethium
-147 and later tritium
. Because of safety concerns and tighter regulation, consumer products such as clocks and watches now increasingly use phosphorescent rather than radioluminescent substances. Radioluminescent paint may still be preferred in specialist applications, such as diving watch
es.
Paint
Paint is any liquid, liquefiable, or mastic composition which after application to a substrate in a thin layer is converted to an opaque solid film. One may also consider the digital mimicry thereof...
that exhibits luminescence
Luminescence
Luminescence is emission of light by a substance not resulting from heat; it is thus a form of cold body radiation. It can be caused by chemical reactions, electrical energy, subatomic motions, or stress on a crystal. This distinguishes luminescence from incandescence, which is light emitted by a...
. In other words, it gives off visible
Visible spectrum
The visible spectrum is the portion of the electromagnetic spectrum that is visible to the human eye. Electromagnetic radiation in this range of wavelengths is called visible light or simply light. A typical human eye will respond to wavelengths from about 390 to 750 nm. In terms of...
light
Light
Light or visible light is electromagnetic radiation that is visible to the human eye, and is responsible for the sense of sight. Visible light has wavelength in a range from about 380 nanometres to about 740 nm, with a frequency range of about 405 THz to 790 THz...
through fluorescence
Fluorescence
Fluorescence is the emission of light by a substance that has absorbed light or other electromagnetic radiation of a different wavelength. It is a form of luminescence. In most cases, emitted light has a longer wavelength, and therefore lower energy, than the absorbed radiation...
, phosphorescence
Phosphorescence
Phosphorescence is a specific type of photoluminescence related to fluorescence. Unlike fluorescence, a phosphorescent material does not immediately re-emit the radiation it absorbs. The slower time scales of the re-emission are associated with "forbidden" energy state transitions in quantum...
, or radioluminescence
Radioluminescence
Radioluminescence is the phenomenon by which luminescence is produced in a material by the bombardment of ionizing radiation such as beta particles.-Tritium:...
.
Fluorescent paint
Ultraviolet
Ultraviolet light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than X-rays, in the range 10 nm to 400 nm, and energies from 3 eV to 124 eV...
(UV) radiation, commonly known as black light
Black light
A black light, also referred to as a UV light, ultraviolet light, or Wood's lamp, is a lamp that emits ultraviolet radiation in the long-wave range, and little visible light...
. Through the mechanism of fluorescence
Fluorescence
Fluorescence is the emission of light by a substance that has absorbed light or other electromagnetic radiation of a different wavelength. It is a form of luminescence. In most cases, emitted light has a longer wavelength, and therefore lower energy, than the absorbed radiation...
, UV-sensitive pigment
Pigment
A pigment is a material that changes the color of reflected or transmitted light as the result of wavelength-selective absorption. This physical process differs from fluorescence, phosphorescence, and other forms of luminescence, in which a material emits light.Many materials selectively absorb...
s present in the paint absorb black light and give off visible light
Visible spectrum
The visible spectrum is the portion of the electromagnetic spectrum that is visible to the human eye. Electromagnetic radiation in this range of wavelengths is called visible light or simply light. A typical human eye will respond to wavelengths from about 390 to 750 nm. In terms of...
in return.
There are two basic kinds of fluorescent paint: visible and invisible. Visible fluorescent paint can appear any bright color under white
White
White is a color, the perception of which is evoked by light that stimulates all three types of color sensitive cone cells in the human eye in nearly equal amounts and with high brightness compared to the surroundings. A white visual stimulation will be void of hue and grayness.White light can be...
light, and glows brilliantly under black light. Invisible fluorescent paint appears white or clear under white light, but glows a particular color—depending on the pigment used—under black light.
This type of paint has extensive applications in the entertainment industry, and it can be used to create black light effects such as invisible images, dual images, day–night transitions, and 3-D effects.
Phosphorescent paint
PhosphorescentPhosphorescence
Phosphorescence is a specific type of photoluminescence related to fluorescence. Unlike fluorescence, a phosphorescent material does not immediately re-emit the radiation it absorbs. The slower time scales of the re-emission are associated with "forbidden" energy state transitions in quantum...
paint is commonly called "glow-in-the-dark" paint. It is made from phosphors such as silver-activated zinc sulfide
Zinc sulfide
Zinc sulfide is a inorganic compound with the formula ZnS. ZnS is the main form of zinc in nature, where it mainly occurs as the mineral sphalerite...
or, more recently, doped
Doping (semiconductor)
In semiconductor production, doping intentionally introduces impurities into an extremely pure semiconductor for the purpose of modulating its electrical properties. The impurities are dependent upon the type of semiconductor. Lightly and moderately doped semiconductors are referred to as extrinsic...
strontium aluminate
Strontium aluminate
Strontium aluminate is a solid odorless, nonflammable, pale yellow powder, heavier than water. It is chemically and biologically inert. When activated with a suitable dopant , it acts as a photoluminescent phosphor with long persistence of phosphorescence...
, and typically glows a pale green to greenish blue color. The mechanism for producing light is similar to that of fluorescent paint, but the emission of visible light persists for some time after it has been exposed to light. Phosphorescent paints have a sustained glow which lasts for some minutes or hours after exposure to light, but will eventually fade over time.
This type of paint has been used to mark escape paths in aircraft and for decorative use, such as "stars" applied to walls and ceilings. It is also increasingly used as an alternative to radioluminescent paint. Kenner
Kenner
Kenner Products was a toy company founded in 1947 by three brothers, Albert, Phillip, and Joseph L. Steiner, in Cincinnati, Ohio, United States, and was named after the street where the original corporate offices were located, which is just north of Cincinnati's Union Terminal.Kenner introduced its...
's Lightning Bug Glo-Juice was a popular non-toxic paint product in 1968, marketed at children, alongside other glow-in-the-dark toys and novelties.
Applications of phosphorescent paints or coatings
When applied as a paint or a more sophisticated coating (e.g. a thermal barrier coating), phosphorescence can be used for temperature detection or degradation measurements. This type of temperature detection is also known as phosphor thermometryPhosphor thermometry
Phosphor thermometry is an optical method for surface temperature measurement. The method exploits luminescence emitted by phosphor material. Phosphors are fine white or pastel-colored inorganic powders which may be stimulated by any of a variety of means to luminesce, i.e. emit light...
.
Radioluminescent paint
Radioluminescent paint contains a radioactive isotopeIsotope
Isotopes are variants of atoms of a particular chemical element, which have differing numbers of neutrons. Atoms of a particular element by definition must contain the same number of protons but may have a distinct number of neutrons which differs from atom to atom, without changing the designation...
(radionuclide
Radionuclide
A radionuclide is an atom with an unstable nucleus, which is a nucleus characterized by excess energy available to be imparted either to a newly created radiation particle within the nucleus or to an atomic electron. The radionuclide, in this process, undergoes radioactive decay, and emits gamma...
) combined with a radioluminescent
Radioluminescence
Radioluminescence is the phenomenon by which luminescence is produced in a material by the bombardment of ionizing radiation such as beta particles.-Tritium:...
substance. The isotopes selected are typically strong emitters of fast electron
Electron
The electron is a subatomic particle with a negative elementary electric charge. It has no known components or substructure; in other words, it is generally thought to be an elementary particle. An electron has a mass that is approximately 1/1836 that of the proton...
s (beta radiation
Beta decay
In nuclear physics, beta decay is a type of radioactive decay in which a beta particle is emitted from an atom. There are two types of beta decay: beta minus and beta plus. In the case of beta decay that produces an electron emission, it is referred to as beta minus , while in the case of a...
), preferred since this radiation will not penetrate an enclosure. Radioluminescent paints will glow without exposure to light until the radioactive isotope has decayed (or the paint itself degrades), which may be many years. They are therefore sometimes referred to as "self-luminous".
Radioluminescent paint was invented in 1908 and originally incorporated radium
Radium
Radium is a chemical element with atomic number 88, represented by the symbol Ra. Radium is an almost pure-white alkaline earth metal, but it readily oxidizes on exposure to air, becoming black in color. All isotopes of radium are highly radioactive, with the most stable isotope being radium-226,...
-226. The toxicity of radium was not initially understood, and radium-based paint saw widespread use in, for example, watches and aircraft instruments. During the 1920s and 1930s, the harmful effects of this paint became increasingly clear. A notorious case involved the "Radium Girls
Radium Girls
The Radium Girls were female factory workers who contracted radiation poisoning from painting watch dials with glow-in-the-dark paint at the United States Radium factory in Orange, New Jersey around 1917....
", a group of women who painted watchfaces and later suffered adverse health effects from ingestion. It is now recognised that radium paint requires great care in application, maintenance and disposal to avoid creation of a hazardous condition.
In the second half of the 20th century, radium was progressively replaced by safer radionuclides such as promethium
Promethium
Promethium is a chemical element with the symbol Pm and atomic number 61. It is notable for being the only exclusively radioactive element besides technetium that is followed by chemical elements with stable isotopes.- Prediction :...
-147 and later tritium
Tritium
Tritium is a radioactive isotope of hydrogen. The nucleus of tritium contains one proton and two neutrons, whereas the nucleus of protium contains one proton and no neutrons...
. Because of safety concerns and tighter regulation, consumer products such as clocks and watches now increasingly use phosphorescent rather than radioluminescent substances. Radioluminescent paint may still be preferred in specialist applications, such as diving watch
Diving watch
A diving watch is a watch designed for underwater diving that features, as a minimum, a water resistance greater than , the equivalent of . The typical diver's watch will have a water resistance of around , though modern technology allows the creation of diving watches that can go much deeper...
es.
See also
- ChromaFlairChromaFlairChromaFlair is the registered trademark for 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...
, a pigment with flakes that interfere with the reflection and refraction of light