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Black light paint or black light fluorescent paint is
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 ...
that glows under a
black light
A blacklight, also called a UV-A light, Wood's lamp, or ultraviolet light, is a lamp that emits long-wave (UV-A) ultraviolet light and very little visible light. One type of lamp has a violet filter material, either on the bulb or in a separat ...
. It is based on
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 ...
s that respond to
light
Light or visible light is electromagnetic radiation that can be perceived by the human eye. Visible light is usually defined as having wavelengths in the range of 400–700 nanometres (nm), corresponding to frequencies of 750–420 tera ...
in the
ultraviolet
Ultraviolet (UV) is a form of electromagnetic radiation with wavelength from 10 nanometer, nm (with a corresponding frequency around 30 Hertz, PHz) to 400 nm (750 Hertz, THz), shorter than that of visible light, but longer than ...
segment of the
electromagnetic spectrum
The electromagnetic spectrum is the range of frequencies (the spectrum) of electromagnetic radiation and their respective wavelengths and photon energies.
The electromagnetic spectrum covers electromagnetic waves with frequencies ranging from ...
. The paint may or may not be colorful under ordinary light. Black light paint should not be confused with
phosphorescent
Phosphorescence is a type of photoluminescence related to fluorescence. When exposed to light (radiation) of a shorter wavelength, a phosphorescent substance will glow, absorbing the light and reemitting it at a longer wavelength. Unlike fluor ...
(glow-in-the-dark) or daylight fluorescent paint.
History
The invention of black light paint is attributed to brothers Joseph and
Robert Switzer in the 1930s. After a fall, Robert suffered a severe head injury that resulted in a severed optic nerve. His doctor confined him to a dark room while he waited for his sight to recover. Joseph, who was a
chemistry
Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science that covers the Chemical element, elements that make up matter to the chemical compound, compounds made of atoms, molecules and ions ...
major at the
University of California, Berkeley
The University of California, Berkeley (UC Berkeley, Berkeley, Cal, or California) is a public land-grant research university in Berkeley, California. Established in 1868 as the University of California, it is the state's first land-grant u ...
, worked with Robert to investigate fluorescent compounds. They brought a
black light
A blacklight, also called a UV-A light, Wood's lamp, or ultraviolet light, is a lamp that emits long-wave (UV-A) ultraviolet light and very little visible light. One type of lamp has a violet filter material, either on the bulb or in a separat ...
into the storeroom of their father's drugstore looking for naturally fluorescing organic compounds and mixed those compounds with
shellac
Shellac () is a resin secreted by the female lac bug on trees in the forests of India and Thailand. It is processed and sold as dry flakes and dissolved in alcohol to make liquid shellac, which is used as a brush-on colorant, food glaze and ...
to develop the first black light fluorescent paints. The first use of these paints was for Joseph's amateur magic shows.
The brothers founded the Fluor-S-Art Company, later named
Day-Glo Color Corp., to develop and sell their products.
‘Day-Glo’ is a registered trademark of the
Day-Glo Color Corporation.
The first commercial uses of black light fluorescent paints were for store displays and movie theaters. During World War II, black light fluorescent paints were used on U.S. naval carriers to allow planes to land at night.
Characteristics and uses
Black light paints and
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. Thicker ...
s are commonly used in the production of
black light posters. Under daylight, the poster may or may not be vibrant in color, but under black light (with little or no visible light present), the effect produced can be
psychedelic
Psychedelics are a subclass of hallucinogenic drugs whose primary effect is to trigger non-ordinary states of consciousness (known as psychedelic experiences or "trips").Pollan, Michael (2018). ''How to Change Your Mind: What the New Science of ...
. The inks are normally highly sensitive to direct sunlight and other powerful light sources. The fluorescent dyes cause a chemical reaction when exposed to high intensity light sources (HILS) and the visual result is a fading in the colors of the inks. With paper, significant visible change in the color saturation can typically be observed within 45 minutes to one hour of exposure to the HILS. To date, there is no absolute method to prevent this phenomenon, although certain laminations, lacquer coatings and glass or plastic protective sheets can effectively slow the fading characteristics of the dyes.
Other common usage of the black light pigments is in security features of money notes, various certificates printed on paper, meal coupons, tickets and similar things that represent a value (monetary or otherwise). The black light printed figures used for this purpose are usually invisible under normal lighting, even when they are exposed to direct sunlight (which contains ultraviolet light) but they show up glowing when exposed to black light source. This defeats simple and inexpensive attempts to counterfeit them by scanning the original using a high resolution scanner and printing them using an inexpensive high resolution printer (most if not all inexpensive printers do not allow using black light inks for printing) and no special equipment is needed to verify the presence and correctness of this feature (an inexpensive black light source being all that is required). Some coupons and tickets use colorful black light inks.
On many German locomotives the control panel labels were printed with black light paint and a black light source was provided in the cab. This left the driver with full
night vision
Night vision is the ability to see in low-light conditions, either naturally with scotopic vision or through a night-vision device. Night vision requires both sufficient spectral range and sufficient intensity range. Humans have poor night vi ...
while still enabling him to distinguish between the different switches and levers to operate his locomotive.
Black light paints are sometimes used in the scenery of
amusement park
An amusement park is a park that features various attractions, such as rides and games, as well as other events for entertainment purposes. A theme park is a type of amusement park that bases its structures and attractions around a central ...
dark ride
A dark ride or ghost train is an indoor amusement ride on which passengers aboard guided vehicles travel through specially lit scenes that typically contain Animatronics, animation, sound, music and Special effect#Live special effects, special e ...
s: a black light illuminates the vivid colors of the scenery, while the vehicle and other passengers remain dimly lit or barely visible. This can enhance the effect of being in a
fantasy world
A fantasy world is a world created for/from fictional media, such as literature, film or games. Typical fantasy worlds involve magic or magical abilities, nonexistent technology and, sometimes, either a historical or futuristic theme. Some wor ...
.
Black light paints may be
fluorescent
Fluorescence is the emission of light by a substance that has absorbed light or other electromagnetic radiation. It is a form of luminescence. In most cases, the emitted light has a longer wavelength, and therefore a lower photon energy, tha ...
or, more rarely,
phosphorescent
Phosphorescence is a type of photoluminescence related to fluorescence. When exposed to light (radiation) of a shorter wavelength, a phosphorescent substance will glow, absorbing the light and reemitting it at a longer wavelength. Unlike fluor ...
, containing a
phosphor
A phosphor is a substance that exhibits the phenomenon of luminescence; it emits light when exposed to some type of radiant energy. The term is used both for fluorescent or phosphorescent substances which glow on exposure to ultraviolet or vi ...
that continues to glow for a time after the black light has been removed. Black light paint can be mixed with similar shades of normal pigments, ‘brightening’ them when viewed in sunlight.
References
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Paints
Inks
Printing materials