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A blacklight, also called a UV-A light, Wood's lamp, or ultraviolet light, is a
lamp Lamp, Lamps or LAMP may refer to: Lighting * Oil lamp, using an oil-based fuel source * Kerosene lamp, using kerosene as a fuel * Electric lamp, or light bulb, a replaceable component that produces light from electricity * Light fixture, or li ...
that emits long-wave (
UV-A 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 ...
)
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 ...
and very little
visible 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 te ...
. One type of lamp has a violet
filter Filter, filtering or filters may refer to: Science and technology Computing * Filter (higher-order function), in functional programming * Filter (software), a computer program to process a data stream * Filter (video), a software component tha ...
material, either on the bulb or in a separate glass filter in the lamp housing, which blocks most visible light and allows through UV, so the lamp has a dim violet glow when operating. Blacklight lamps which have this filter have a lighting industry designation that includes the letters "BLB". This stands for "blacklight blue". A second type of lamp produces ultraviolet but does not have the filter material, so it produces more visible light and has a blue color when operating. These tubes are made for use in "
bug zapper A bug zapper, more formally called an electrical discharge insect control system, electric insect killer or (insect) electrocutor trap, is a device that attracts and kills flying insects that are attracted by light. A light source attracts insect ...
" insect traps, and are identified by the industry designation "BL". This stands for "blacklight". Blacklight sources may be specially designed
fluorescent lamp A fluorescent lamp, or fluorescent tube, is a low-pressure mercury-vapor gas-discharge lamp that uses fluorescence to produce visible light. An electric current in the gas excites mercury vapor, which produces short-wave ultraviolet lig ...
s,
mercury-vapor lamp A mercury-vapor lamp is a gas-discharge lamp that uses an electric arc through vaporized mercury to produce light. The arc discharge is generally confined to a small fused quartz arc tube mounted within a larger soda lime or borosilicate glass ...
s,
light-emitting diodes A light-emitting diode (LED) is a semiconductor device that emits light when current flows through it. Electrons in the semiconductor recombine with electron holes, releasing energy in the form of photons. The color of the light (cor ...
(LEDs),
lasers A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The word "laser" is an acronym for "light amplification by stimulated emission of radiation". The fir ...
, or
incandescent lamp An incandescent light bulb, incandescent lamp or incandescent light globe is an electric light with a wire filament heated until it glows. The filament is enclosed in a glass bulb with a vacuum or inert gas to protect the filament from oxid ...
s. In
medicine Medicine is the science and practice of caring for a patient, managing the diagnosis, prognosis, prevention, treatment, palliation of their injury or disease, and promoting their health. Medicine encompasses a variety of health care pract ...
,
forensics Forensic science, also known as criminalistics, is the application of science to criminal and civil laws, mainly—on the criminal side—during criminal investigation, as governed by the legal standards of admissible evidence and crimina ...
, and some other scientific fields, such a light source is referred to as a Wood's lamp, named after
Robert Williams Wood Robert Williams Wood (May 2, 1868 – August 11, 1955) was an American physicist and inventor who made pivotal contributions to the field of optics. He pioneered infrared and ultraviolet photography. Wood's patents and theoretical work inform mo ...
, who invented the original
Wood's glass Wood's glass is an optical filter glass invented in 1903 by American physicist Robert Williams Wood (1868–1955), which allows ultraviolet and infrared light Infrared (IR), sometimes called infrared light, is electromagnetic radiation ...
UV filters. Although many other types of lamp emit ultraviolet light with visible light, black lights are essential when UV-A light without visible light is needed, particularly in observing
fluorescence 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 ...
, the colored glow that many substances emit when exposed to UV. Black lights are employed for decorative and artistic lighting effects, diagnostic and therapeutic uses in medicine, the detection of substances tagged with
fluorescent dye A fluorophore (or fluorochrome, similarly to a chromophore) is a fluorescent chemical compound that can re-emit light upon light excitation. Fluorophores typically contain several combined aromatic groups, or planar or cyclic molecules with se ...
s, rock-hunting, the detection of
counterfeit money Counterfeit money is currency produced without the legal sanction of a state or government, usually in a deliberate attempt to imitate that currency and so as to deceive its recipient. Producing or using counterfeit money is a form of fraud or fo ...
, the curing of plastic resins, attracting insects and the detection of
refrigerant A refrigerant is a working fluid used in the heat pump and refrigeration cycle, refrigeration cycle of air conditioning systems and heat pumps where in most cases they undergo a repeated phase transition from a liquid to a gas and back again. Ref ...
leaks affecting
refrigerator A refrigerator, colloquially fridge, is a commercial and home appliance consisting of a thermally insulated compartment and a heat pump (mechanical, electronic or chemical) that transfers heat from its inside to its external environment so th ...
s and
air conditioning Air conditioning, often abbreviated as A/C or AC, is the process of removing heat from an enclosed space to achieve a more comfortable interior environment (sometimes referred to as 'comfort cooling') and in some cases also strictly controlling ...
systems. Strong sources of long-wave ultraviolet light are used in
tanning bed Indoor tanning involves using a device that emits ultraviolet radiation to produce a cosmetic tan. Typically found in tanning salons, gyms, spas, hotels, and sporting facilities, and less often in private residences, the most common device is a ho ...
s. UV-A presents a potential hazard when eyes and skin are exposed, especially to high power sources. According to the
World Health Organization The World Health Organization (WHO) is a specialized agency of the United Nations responsible for international public health. The WHO Constitution states its main objective as "the attainment by all peoples of the highest possible level of h ...
, UV-A is responsible for the initial tanning of skin and it contributes to skin ageing and wrinkling. UV-A may also contribute to the progression of skin cancers. Additionally, UV-A can have negative effects on eyes in both the short-term and long-term.


Types


Fluorescent

Fluorescent black light tubes are typically made in the same fashion as normal
fluorescent tube A fluorescent lamp, or fluorescent tube, is a low-pressure mercury-vapor gas-discharge lamp that uses fluorescence to produce visible light. An electric current in the gas excites mercury vapor, which produces short-wave ultraviolet ligh ...
s except that 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 emits UVA light instead of visible white light is used on the inside of the tube. The type most commonly used for black lights, designated blacklight blue or "BLB" by the industry, has a dark blue filter coating on the tube, which filters out most visible light, so that
fluorescence 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 ...
effects can be observed. These tubes have a dim violet glow when operating. They should not be confused with "blacklight" or "BL" tubes, which have no filter coating, and have a brighter blue color. These are made for use in "
bug zapper A bug zapper, more formally called an electrical discharge insect control system, electric insect killer or (insect) electrocutor trap, is a device that attracts and kills flying insects that are attracted by light. A light source attracts insect ...
" insect traps where the emission of visible light does not interfere with the performance of the product. The phosphor typically used for a near 368 to 371 nanometer emission peak is either
europium Europium is a chemical element with the symbol Eu and atomic number 63. Europium is the most reactive lanthanide by far, having to be stored under an inert fluid to protect it from atmospheric oxygen or moisture. Europium is also the softest lanth ...
-doped
strontium fluoroborate Strontium is the chemical element with the symbol Sr and atomic number 38. An alkaline earth metal, strontium is a soft silver-white yellowish metallic element that is highly chemically reactive. The metal forms a dark oxide layer when it is ex ...
(:) or europium-doped
strontium borate Strontium is the chemical element with the symbol Sr and atomic number 38. An alkaline earth metal, strontium is a soft silver-white yellowish metallic element that is highly chemically reactive. The metal forms a dark oxide layer when it is ex ...
(:) while the phosphor used to produce a peak around 350 to 353 nanometres is lead-doped
barium silicate Barium is a chemical element with the symbol Ba and atomic number 56. It is the fifth element in group 2 and is a soft, silvery alkaline earth metal. Because of its high chemical reactivity, barium is never found in nature as a free element. Th ...
(:). "Blacklight blue" lamps peak at 365 nm. Manufacturers use different numbering systems for black light tubes. Philips uses one system which is becoming outdated (2010), while the (German)
Osram Osram Licht AG is a German company that makes electric lights, headquartered in Munich and Premstätten (Austria). Osram positions itself as a high-tech photonics company that is increasingly focusing on sensor technology, visualization and tre ...
system is becoming dominant outside North America. The following table lists the tubes generating blue, UVA and UVB, in order of decreasing wavelength of the most intense peak. Approximate phosphor compositions, major manufacturer's type numbers and some uses are given as an overview of the types available. "Peak" position is approximated to the nearest 10 nm. "Width" is the measure between points on the shoulders of the peak that represent 50% intensity.


"Bug zapper" tubes

Another class of UV fluorescent bulb is designed for use in "
bug zapper A bug zapper, more formally called an electrical discharge insect control system, electric insect killer or (insect) electrocutor trap, is a device that attracts and kills flying insects that are attracted by light. A light source attracts insect ...
" flying insect traps. Insects are attracted to the UV light, which they are able to see, and are then
electrocute Electrocution is death or severe injury caused by electric shock from electric current passing through the body. The word is derived from "electro" and "execution", but it is also used for accidental death. The term "electrocution" was coined ...
d by the device. These bulbs use the same UV-A emitting phosphor blend as the filtered blacklight, but since they do not need to suppress visible light output, they do not use a purple filter material in the bulb. Plain glass blocks out less of the visible mercury emission spectrum, making them appear light blue-violet to the naked eye. These lamps are referred to by the designation "blacklight" or "BL" in some North American lighting catalogs. These types are not suitable for applications which require the low visible light output of "BLB" tubes lamps.


Incandescent

A black light may also be formed by simply using a UV filter coating such as
Wood's glass Wood's glass is an optical filter glass invented in 1903 by American physicist Robert Williams Wood (1868–1955), which allows ultraviolet and infrared light Infrared (IR), sometimes called infrared light, is electromagnetic radiation ...
on the envelope of a common
incandescent bulb An incandescent light bulb, incandescent lamp or incandescent light globe is an electric light with a wire filament heated until it glows. The filament is enclosed in a glass bulb with a vacuum or inert gas to protect the filament from oxida ...
. This was the method that was used to create the very first black light sources. Although incandescent black light bulbs are a cheaper alternative to fluorescent tubes, they are exceptionally inefficient at producing UV light since most of the light emitted by the filament is visible light which must be blocked. Due to its
black body A black body or blackbody is an idealized physical body that absorbs all incident electromagnetic radiation, regardless of frequency or angle of incidence. The name "black body" is given because it absorbs all colors of light. A black body ...
spectrum, an incandescent light radiates less than 0.1% of its energy as UV light. Incandescent UV bulbs, due to the necessary absorption of the visible light, become very hot during use. This heat is, in fact, encouraged in such bulbs, since a hotter filament increases the proportion of UVA in the black-body radiation emitted. This high running-temperature drastically reduces the life of the lamp, however, from a typical 1,000 hours to around 100 hours.


Mercury vapor

High power mercury vapor black light lamps are made in power ratings of 100 to 1,000 watts. These do not use phosphors, but rely on the intensified and slightly broadened 350–375 nm spectral line of mercury from high pressure discharge at between , depending upon the specific type. These lamps use envelopes of Wood's glass or similar optical filter coatings to block out all the visible light and also the short wavelength (UVC) lines of mercury at 184.4 and 253.7 nm, which are harmful to the eyes and skin. A few other spectral lines, falling within the pass band of the Wood's glass between 300 and 400 nm, contribute to the output. These lamps are used mainly for theatrical purposes and concert displays. They are more efficient UVA producers per unit of power consumption than fluorescent tubes.


LED

Ultraviolet light can be generated by some
light-emitting diode A light-emitting diode (LED) is a semiconductor device that emits light when current flows through it. Electrons in the semiconductor recombine with electron holes, releasing energy in the form of photons. The color of the light (cor ...
s, but wavelengths shorter than 380 nm are uncommon, and the emission peaks are broad, so only the very lowest energy UV
photons A photon () is an elementary particle that is a quantum of the electromagnetic field, including electromagnetic radiation such as light and radio waves, and the force carrier for the electromagnetic force. Photons are massless, so they alway ...
are emitted, within predominant not visible light.


Safety

Although black lights produce light in the UV range, their spectrum is mostly confined to the longwave UVA region, that is, UV radiation nearest in wavelength to visible light, with low frequency and therefore relatively low energy. While low, there is still some power of a conventional black light in the UVB range. UVA is the safest of the three spectra of UV light, although high exposure to UVA has been linked to the development of
skin cancer Skin cancers are cancers that arise from the skin. They are due to the development of abnormal cells that have the ability to invade or spread to other parts of the body. There are three main types of skin cancers: basal-cell skin cancer (BCC) ...
in humans. The relatively low energy of UVA light does not cause
sunburn Sunburn is a form of radiation burn that affects living tissue, such as skin, that results from an overexposure to ultraviolet (UV) radiation, usually from the Sun. Common symptoms in humans and animals include: red or reddish skin that is ho ...
. UVA is capable of causing damage to
collagen Collagen () is the main structural protein in the extracellular matrix found in the body's various connective tissues. As the main component of connective tissue, it is the most abundant protein in mammals, making up from 25% to 35% of the whole ...
fibers, however, so it does have the potential to accelerate
skin Skin is the layer of usually soft, flexible outer tissue covering the body of a vertebrate animal, with three main functions: protection, regulation, and sensation. Other cuticle, animal coverings, such as the arthropod exoskeleton, have diffe ...
aging and cause
wrinkle A wrinkle, also known as a rhytid, is a fold, ridge or crease in an otherwise smooth surface, such as on skin or fabric. Skin wrinkles typically appear as a result of ageing processes such as glycation, habitual sleeping positions, loss of ...
s. UVA can also destroy
vitamin A Vitamin A is a fat-soluble vitamin and an essential nutrient for humans. It is a group of organic compounds that includes retinol, retinal (also known as retinaldehyde), retinoic acid, and several provitamin A carotenoids (most notably bet ...
in the skin. UVA light has been shown to cause
DNA damage DNA repair is a collection of processes by which a cell identifies and corrects damage to the DNA molecules that encode its genome. In human cells, both normal metabolic activities and environmental factors such as radiation can cause DNA da ...
, but not directly, like UVB and UVC. Due to its longer
wavelength In physics, the wavelength is the spatial period of a periodic wave—the distance over which the wave's shape repeats. It is the distance between consecutive corresponding points of the same phase on the wave, such as two adjacent crests, tro ...
, it is absorbed less and reaches deeper into
skin layers The human skin is the outer covering of the body and is the largest organ of the integumentary system. The skin has up to seven layers of ectodermal tissue guarding muscles, bones, ligaments and internal organs. Human skin is similar to mos ...
, where it produces reactive chemical intermediates such as
hydroxyl In chemistry, a hydroxy or hydroxyl group is a functional group with the chemical formula and composed of one oxygen atom covalently bonded to one hydrogen atom. In organic chemistry, alcohols and carboxylic acids contain one or more hydroxy ...
and oxygen radicals, which in turn can damage DNA and result in a risk of
melanoma Melanoma, also redundantly known as malignant melanoma, is a type of skin cancer that develops from the pigment-producing cells known as melanocytes. Melanomas typically occur in the skin, but may rarely occur in the mouth, intestines, or eye ( ...
. The weak output of black lights, however, is not considered sufficient to cause DNA damage or cellular
mutation In biology, a mutation is an alteration in the nucleic acid sequence of the genome of an organism, virus, or extrachromosomal DNA. Viral genomes contain either DNA or RNA. Mutations result from errors during DNA or viral replication, mi ...
s in the way that direct summer sunlight can, although there are reports that overexposure to the type of UV radiation used for creating artificial suntans on sunbeds can cause DNA damage, photoaging (damage to the skin from prolonged exposure to sunlight), toughening of the skin, suppression of the immune system, cataract formation and skin cancer. UV-A can have negative effects on eyes in both the short-term and long-term.


Uses

Ultraviolet radiation is invisible to the human eye, but illuminating certain materials with UV radiation causes the emission of visible light, causing these substances to glow with various colors. This is called ''
fluorescence 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 ...
'', and has many practical uses. Black lights are required to observe fluorescence, since other types of ultraviolet lamps emit visible light which drowns out the dim fluorescent glow.


Medical applications

A Wood's lamp is a diagnostic tool used in
dermatology Dermatology is the branch of medicine dealing with the skin.''Random House Webster's Unabridged Dictionary.'' Random House, Inc. 2001. Page 537. . It is a speciality with both medical and surgical aspects. A dermatologist is a specialist medical ...
by which
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 ...
is shone (at a wavelength of approximately 365 nanometers) onto the skin of the patient; a technician then observes any subsequent
fluorescence 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 ...
. For example,
porphyrins Porphyrins ( ) are a group of heterocyclic macrocycle organic compounds, composed of four modified pyrrole subunits interconnected at their α carbon atoms via methine bridges (=CH−). The parent of porphyrin is porphine, a rare chemical compo ...
—associated with some skin diseases—will fluoresce pink. Though the technique for producing a source of ultraviolet light was devised by
Robert Williams Wood Robert Williams Wood (May 2, 1868 – August 11, 1955) was an American physicist and inventor who made pivotal contributions to the field of optics. He pioneered infrared and ultraviolet photography. Wood's patents and theoretical work inform mo ...
in 1903 using "
Wood's glass Wood's glass is an optical filter glass invented in 1903 by American physicist Robert Williams Wood (1868–1955), which allows ultraviolet and infrared light Infrared (IR), sometimes called infrared light, is electromagnetic radiation ...
", it was in 1925 that the technique was used in
dermatology Dermatology is the branch of medicine dealing with the skin.''Random House Webster's Unabridged Dictionary.'' Random House, Inc. 2001. Page 537. . It is a speciality with both medical and surgical aspects. A dermatologist is a specialist medical ...
by Margarot and Deveze for the detection of fungal infection of hair. It has many uses, both in distinguishing fluorescent conditions from other conditions and in locating the precise boundaries of the condition.


Fungal and bacterial infections

It is also helpful in diagnosing: *
Fungal infections Fungal infection, also known as mycosis, is disease caused by fungi. Different types are traditionally divided according to the part of the body affected; superficial, subcutaneous, and systemic. Superficial fungal infections include common ti ...
. Some forms of
tinea Dermatophytosis, also known as ringworm, is a fungal infection of the skin. Typically it results in a red, itchy, scaly, circular rash. Hair loss may occur in the area affected. Symptoms begin four to fourteen days after exposure. Multiple ar ...
, such as ''
Trichophyton tonsurans ''Trichophyton tonsurans'' is a fungus in the family Arthrodermataceae that causes ringworm infection of the scalp. It was first recognized by David Gruby in 1844. Isolates are characterized as the "–" or negative mating type of the '' Arthrode ...
'', do not fluoresce. *
Bacterial 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 ...
infections **'' Corynebacterium minutissimum'' is coral red **''
Pseudomonas ''Pseudomonas'' is a genus of Gram-negative, Gammaproteobacteria, belonging to the family Pseudomonadaceae and containing 191 described species. The members of the genus demonstrate a great deal of metabolic diversity and consequently are able ...
'' is yellow-green * ''
Cutibacterium acnes ''Cutibacterium acnes'' (formerly ''Propionibacterium acnes'') is the relatively slow-growing, typically aerotolerant Anaerobic organism, anaerobic, gram-positive bacterium (rod) linked to the skin condition of acne vulgaris, acne; it can also ca ...
'', a bacterium involved in
acne Acne, also known as ''acne vulgaris'', is a long-term Cutaneous condition, skin condition that occurs when Keratinocyte, dead skin cells and Sebum, oil from the skin clog hair follicles. Typical features of the condition include comedo, black ...
causation, exhibits an orange glow under a Wood's lamp.


Ethylene glycol poisoning

A Wood's lamp may be used to rapidly assess whether an individual is suffering from
ethylene glycol poisoning Ethylene glycol poisoning is poisoning caused by drinking ethylene glycol. Early symptoms include Substance intoxication, intoxication, vomiting and abdominal pain. Later symptoms may include a decreased level of consciousness, headache, and seiz ...
as a consequence of
antifreeze An antifreeze is an additive which lowers the freezing point of a water-based liquid. An antifreeze mixture is used to achieve freezing-point depression for cold environments. Common antifreezes also increase the boiling point of the liquid, all ...
ingestion. Manufacturers of ethylene glycol-containing antifreezes commonly add
fluorescein Fluorescein is an organic compound and dye based on the xanthene tricyclic structural motif, formally belonging to triarylmethine dyes family. It is available as a dark orange/red powder slightly soluble in water and alcohol. It is widely used ...
, which causes the patient's urine to
fluoresce 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 ...
under Wood's lamp.


Other

Wood's lamp is useful in diagnosing conditions such as
tuberous sclerosis Tuberous sclerosis complex (TSC) is a rare multisystem autosomal dominant genetic disease that causes non-cancerous tumours to grow in the brain and on other vital organs such as the kidneys, heart, liver, eyes, lungs and skin. A combination ...
and
erythrasma Erythrasma is a superficial skin infection that causes brown, scaly skin patches. It is caused by '' Corynebacterium minutissimum'' bacteria, a normal part of skin flora (the microorganisms that are normally present on the skin). There are two ty ...
(caused by ''Corynebacterium minutissimum'', see above). Additionally, detection of
porphyria cutanea tarda Porphyria cutanea tarda is the most common subtype of porphyria. The disease is named because it is a porphyria that often presents with skin manifestations later in life. The disorder results from low levels of the enzyme responsible for the fift ...
can sometimes be made when urine turns pink upon illumination with Wood's lamp. Wood's lamps have also been used to differentiate hypopigmentation from depigmentation such as with
vitiligo Vitiligo is a disorder that causes the skin to lose its color. Specific causes are unknown but studies suggest a link to immune system changes. Signs and symptoms The only sign of vitiligo is the presence of pale patchy areas of depigmen ...
. A vitiligo patient's skin will appear yellow-green or blue under the Wood's lamp. Its use in detecting
melanoma Melanoma, also redundantly known as malignant melanoma, is a type of skin cancer that develops from the pigment-producing cells known as melanocytes. Melanomas typically occur in the skin, but may rarely occur in the mouth, intestines, or eye ( ...
has been reported.


See also

Bili light A bili light is a light therapy tool to treat newborn jaundice (hyperbilirubinemia). High levels of bilirubin can cause brain damage (kernicterus), leading to cerebral palsy, auditory neuropathy, gaze abnormalities and dental enamel hypoplasia. T ...
. A type of phototherapy that uses blue light with a range of 420–470 nm, used to treat
neonatal jaundice Neonatal jaundice is a yellowish discoloration of the white part of the eyes and skin in a newborn baby due to high bilirubin levels. Other symptoms may include excess sleepiness or poor feeding. Complications may include seizures, cerebral pals ...
.


Security and authentication

Black light is commonly used to authenticate
oil paintings Oil painting is the process of painting with pigments with a medium of drying oil as the binder. It has been the most common technique for artistic painting on wood panel or canvas for several centuries, spreading from Europe to the rest of ...
,
antique An antique ( la, antiquus; 'old', 'ancient') is an item perceived as having value because of its aesthetic or historical significance, and often defined as at least 100 years old (or some other limit), although the term is often used loosely ...
s and
banknote A banknote—also called a bill (North American English), paper money, or simply a note—is a type of negotiable instrument, negotiable promissory note, made by a bank or other licensed authority, payable to the bearer on demand. Banknotes w ...
s. Black lights can be used to differentiate real currency from
counterfeit To counterfeit means to imitate something authentic, with the intent to steal, destroy, or replace the original, for use in illegal transactions, or otherwise to deceive individuals into believing that the fake is of equal or greater value tha ...
notes because, in many countries, legal banknotes have fluorescent symbols on them that only show under a black light. In addition, the paper used for printing money does not contain any of the brightening agents which cause commercially available papers to fluoresce under black light. Both of these features make illegal notes easier to detect and more difficult to successfully counterfeit. The same security features can be applied to identification cards such as
passports A passport is an official travel document issued by a government that contains a person's identity. A person with a passport can travel to and from foreign countries more easily and access consular assistance. A passport certifies the personal ...
or
driver's licenses A driver's license is a legal authorization, or the official document confirming such an authorization, for a specific individual to operate one or more types of motorized vehicles—such as motorcycles, cars, trucks, or buses—on a public r ...
. Other security applications include the use of pens containing a fluorescent ink, generally with a soft tip, that can be used to "invisibly" mark items. If the objects that are so marked are subsequently stolen, a black light can be used to search for these security markings. At some
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 ...
s,
nightclub A nightclub (music club, discothèque, disco club, or simply club) is an entertainment venue during nighttime comprising a dance floor, lightshow, and a stage for live music or a disc jockey (DJ) who plays recorded music. Nightclubs gener ...
s and at other, day-long (or night-long) events, a fluorescent mark is
rubber stamp A rubber stamp is an image or pattern that has been carved, molded, laser engraved or vulcanized onto a sheet of rubber. Rubber stamping, also called stamping, is a craft in which some type of ink made of dye or pigment is applied to rubber ...
ed onto the wrist of a guest who can then exercise the option of leaving and being able to return again without paying another admission fee.


Biology

Fluorescent materials are also very widely used in numerous applications in molecular biology, often as "tags" which bind themselves to a substance of interest (for example, DNA), so allowing their visualization. Thousands of moth and insect collectors all over the world use various types of black lights to attract moth and insect specimens for photography and collecting. It is one of the preferred light sources for attracting insects and moths at night. Black light can also be used to see animal excreta such as urine and vomit that is not always visible to the naked eye.


Detection of faults

Black light is used extensively in non-destructive testing. Fluorescing fluids are applied to
metal A metal (from Greek μέταλλον ''métallon'', "mine, quarry, metal") is a material that, when freshly prepared, polished, or fractured, shows a lustrous appearance, and conducts electricity and heat relatively well. Metals are typicall ...
structures and illuminated with a black light which allows cracks and other weaknesses in the material to be easily detected. In addition, if a leak is suspected in a
refrigerator A refrigerator, colloquially fridge, is a commercial and home appliance consisting of a thermally insulated compartment and a heat pump (mechanical, electronic or chemical) that transfers heat from its inside to its external environment so th ...
or an
air conditioning Air conditioning, often abbreviated as A/C or AC, is the process of removing heat from an enclosed space to achieve a more comfortable interior environment (sometimes referred to as 'comfort cooling') and in some cases also strictly controlling ...
system, a UV tracer dye can be injected into the system along with the compressor lubricant oil and refrigerant mixture. The system is then run in order to circulate the dye across the piping and components and then the system is examined with a blacklight lamp. Any evidence of fluorescent dye then pinpoints the leaking part which needs replacement.


Decorative and artistic uses

It is also used to illuminate pictures painted with fluorescent colors, particularly on black
velvet Weave details visible on a purple-colored velvet fabric Velvet is a type of woven tufted fabric in which the cut threads are evenly distributed, with a short pile, giving it a distinctive soft feel. By extension, the word ''velvety'' means ...
, which intensifies the illusion of self-illumination. The use of such materials, often in the form of tiles viewed in a
sensory room Sensory may refer to: Biology * Sensory ecology, how organisms obtain information about their environment * Sensory neuron, nerve cell responsible for transmitting information about external stimuli * Sensory perception, the process of acquir ...
under UV light, is common in the United Kingdom for the education of students with profound and multiple learning difficulties. Such fluorescence from certain textile fibers, especially those bearing
optical brightener Optical brighteners, optical brightening agents (OBAs), fluorescent brightening agents (FBAs), or fluorescent whitening agents (FWAs), are chemical compounds that absorb light in the ultraviolet and violet region (usually 340-370 nm) of the ...
residues, can also be used for recreational effect, as seen, for example, in the opening credits of the
James Bond The ''James Bond'' series focuses on a fictional British Secret Service agent created in 1953 by writer Ian Fleming, who featured him in twelve novels and two short-story collections. Since Fleming's death in 1964, eight other authors have ...
film ''
A View to a Kill ''A View to a Kill'' is a 1985 spy film and the fourteenth in the ''James Bond'' series produced by Eon Productions, and is the seventh and final appearance of Roger Moore as the fictional MI6 agent James Bond. Although the title is adapted ...
''. Black light puppetry is also performed in a black light theater.


Mineral identification

Blacklights are a common tool for rock-hunting and identification of
mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. ( ...
s by their fluorescence.


Curing resins


Other

One of the innovations for night and all-weather flying used by the US, UK, Japan and
Germany Germany,, officially the Federal Republic of Germany, is a country in Central Europe. It is the second most populous country in Europe after Russia, and the most populous member state of the European Union. Germany is situated betwe ...
during
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 ...
was the use of UV interior lighting to illuminate the instrument panel, giving a safer alternative to the
radium Radium is a chemical element with the symbol Ra and atomic number 88. It is the sixth element in group 2 of the periodic table, also known as the alkaline earth metals. Pure radium is silvery-white, but it readily reacts with nitrogen (rather t ...
-painted instrument faces and pointers, and an intensity that could be varied easily and without visible illumination that would give away an aircraft's position. This went so far as to include the printing of charts that were marked in UV-fluorescent inks, and the provision of UV-visible
pencils A pencil () is a writing or drawing implement with a solid pigment core in a protective casing that reduces the risk of core breakage, and keeps it from marking the user's hand. Pencils create marks by physical abrasion, leaving a trail ...
and
slide rules The slide rule is a mechanical analog computer which is used primarily for multiplication and division, and for functions such as exponents, roots, logarithms, and trigonometry. It is not typically designed for addition or subtraction, which ...
such as the
E6B The E6B flight computer is a form of circular slide rule used in aviation and one of the very few analog calculating devices in widespread use in the 21st century. They are mostly used in flight training, because these flight computers have b ...
. They may also be used to test for
LSD Lysergic acid diethylamide (LSD), also known colloquially as acid, is a potent psychedelic drug. Effects typically include intensified thoughts, emotions, and sensory perception. At sufficiently high dosages LSD manifests primarily mental, vi ...
, which fluoresces under black light while common substitutes such as 25I-NBOMe do not.The fluorometric determination of lysergic acid diethylamide and ergonovine
A fluorometer was designed to detect very small amounts of LSD and ergonovine. The instrument proved less satisfactory than the Bowman fluorometer. Both LSD and ergonovine lost their fluorescence very rapidly upon strong ultraviolet irradiation. The mechanism involved in this decrease in fluorescence is not known.
Strong sources of long-wave ultraviolet light are used in
tanning bed Indoor tanning involves using a device that emits ultraviolet radiation to produce a cosmetic tan. Typically found in tanning salons, gyms, spas, hotels, and sporting facilities, and less often in private residences, the most common device is a ho ...
s. File:US $20 under blacklight.jpg, The
security thread A security thread is a security feature of many banknotes to protect against counterfeiting, consisting of a thin ribbon that is threaded through the note's paper. Usually, the ribbon runs vertically, and is "woven" into the paper, so that it a ...
of a US $20 bill glows green under black light as a safeguard against
counterfeit To counterfeit means to imitate something authentic, with the intent to steal, destroy, or replace the original, for use in illegal transactions, or otherwise to deceive individuals into believing that the fake is of equal or greater value tha ...
ing. File:PRC E-Passport Info Page under black light.jpg, Anti-counterfeiting design of a
Chinese passport The People's Republic of China Passport (), commonly referred to as the Chinese passport, is a passport issued to citizens of the People's Republic of China (PRC) for the purpose of international travel, and entitles its bearer to the protec ...
glows under black light. File:Sorpion Under Blacklight.jpg,
Scorpion Scorpions are predatory arachnids of the order Scorpiones. They have eight legs, and are easily recognized by a pair of grasping pincers and a narrow, segmented tail, often carried in a characteristic forward curve over the back and always end ...
fluorescing 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 ...
under ultraviolet from a black light File:Ultraschall Club Munich 2001 16.jpg, Decorative use of black light in a
nightclub A nightclub (music club, discothèque, disco club, or simply club) is an entertainment venue during nighttime comprising a dance floor, lightshow, and a stage for live music or a disc jockey (DJ) who plays recorded music. Nightclubs gener ...


See also

*
Blacklight poster A blacklight poster or black light poster is a poster printed with inks which Fluorescence, fluoresce under a black light. The inks used contain phosphors which cause them to glow when exposed to ultraviolet light emitted from black lights. Over ...
*
List of light sources This is a list of sources of light, the visible part of the electromagnetic spectrum. Light sources produce photons from another energy source, such as heat, chemical reactions, or conversion of mass or a different frequency of electromagnetic ener ...


Footnotes


References


External links

* * * * * http://mississippientomologicalmuseum.org.msstate.edu/collecting.preparation.methods/Blacklight.traps.htm {{Skin and subcutaneous tissue procedures American inventions Articles containing video clips Luminescence Types of lamp Ultraviolet radiation