Glow! – 12 Amazing Uses for a UV Flashlight

It is amazing how little of the world we can see with our naked eyes – how little that visible light shows us. Yet these things we can’t see affect our daily lives both positively and negatively. UV light is one of those interesting and amazing things. It can make us healthier, or make us sick. It can strengthen some materials while making others weaker. UV light can enable us to see the world in ways we could not otherwise do. Read on to find out more about this interesting form of energy and some uses for UV Light.

What is UV Light?

UV Light is the spectrum of radiation just beyond the violet color in the color spectrum. UV light is also called ‘blacklight’ for its’ ability to make materials glow without showing a lot of visible light itself.
UV Radiation was discovered by John Ritter in 1801. He conducted an experiment projecting sunlight through a prism and onto photographic (Silver Oxide) paper.
Photographic paper turns black more rapidly in blue and purple light than in red light. The photographic paper turned black in the blue and purple light as expected. However, the area beyond the purple spectrum where there was no visible light also turned black. This proved that there was energy being produced by the sun that was not in the visible light spectrum.
Here is a video that describes this discovery further


Scientists classify Ultraviolet radiation into three categories separated by wavelength measurement in nanometers.
  • UVA, 320nm-400nm, is the closest UV light to the visible spectrum. Most UV lights are UVA, and these are the rays that are responsible for tanning your skin. Flashlights and other UV lights will generally be in this category.
  • UVB, 290nm-320nm, is harmful in prolonged doses. This is the spectrum that causes sunburns and even skin cancer.
  • UVC, 100nm-290nm, is the most dangerous to organic cells. UVC is mostly blocked by the ozone layer so is not a factor in nature. Man-made sources are commonly used for the disinfection of surfaces and water sterilization.
Here’s a YouTube video by James Lincoln which illustrates the differences.

Effects of UV Light

UV light has both positive and negative effects on human health, depending on how it is used and what the exposure levels are.

Positive Effects of UV Light exposure

Some of the positive effects of UV Light include:
  • Vitamin D Synthesis. Vitamin D is generated by your skin’s direct exposure to the sun. I live in a northern climate and this can be difficult during the winter months. Letting the sun kiss your face on a daily basis can avoid a host of health issues.
  • Cancer and Autoimmune Disease Treatment. UVA and UVB rays, sometimes in conjunction with medications, can be used to kill certain cancer cells and treat skin lymphoma.
  • Treatment of Psoriasis and Other Skin Diseases. Phototherapy is defined as therapy using man-made UV lights (as opposed to Heliotherapy which uses the sun’s rays). Phototherapy has shown to be effective in skin disorders such as Psoriasis, Vitiligo, and others that I would have to refer you to a doctor for proper pronunciation.
  • Disinfecting Surfaces, Water, and even the Air. The damaging UVC rays are very useful in disinfecting surfaces and water but are dangerous to human tissue as well. Fortunately, a wavelength band was found (207-222nm) that is not absorbed by the skin but still harmful to viruses and bacteria. This enables UV disinfectant lights to be safely used in public places where germs like to spread, like airports.

Dangers of UV light exposure

  • Sunburn and Premature Aging. Unprotected exposure to UVB rays contributes to sunburns, while the longer UVA rays contribute to premature aging (wrinkles, liver spots, etc.) of the skin. A history of sunburns is a risk factor for serious skin cancers.
  • Skin Cancer. The most common types of skin cancer are found in parts of the body that see the most sun. UV rays from the sun as well as man-made devices such as Tanning Beds and UV lights can increase the risk of skin cancer.
  • Eye Damage. Unprotected doses of UVA rays can damage the back of your eye and cause temporary blindness. Cataracts, macular degeneration, Pterygium (a growth that obscures vision), and other burn damage can occur.
  • Deterioration of Plants and Polymers. Studies have shown high doses of UVB light to be a factor in chlorophyll and cellular degradation in plants. And I know from experience the precautions that we have to take to keep our plastic-based Kayaks out of the sun.
  • Immune System Suppression. High doses of UVB have been shown to suppress the immune system. Sufferers of the Herpes virus can experience outbreaks after being exposed to UV radiation.


Protecting yourself from UV light

It has been said that there is no safe dosage of UV radiation. Given the dangers of long exposure to UV radiation, it is important to take precautions for your health. There are many easy options for absorbing or deflecting a majority of UV radiation including:
  • Sunscreen. Select a broad-spectrum sunscreen that protects against both UVA and UVB radiation. Be sure and follow the manufacturer’s instructions for proper application and protection.
  • Clothing. Even a light base layer of clothing (and gloves!) will protect you from UV rays.
  • Eyeglasses and sunglasses. Glass blocks UV light, even something as simple as an old pane glass window.

It is important to note that cloud cover does not block UV radiation. You can be over-exposed on a cloudy day without realizing it. Also, reflections from snow or water can intensify UV radiation exposure, giving a ‘skiers tan’ on half of your face, or even getting a sunburn below your jaw when on a boat or kayak.

What glows under a UV light?

Now that we understand the benefits and dangers of UV light, we can start discussing how useful UV light can be. Anything that glows under UV light is considered Fluorescent.
  • Fluorescent dyes and inks. Manufacturers add special fluorescent chemicals to dyes and inks for a variety of applications, including marking items discreetly, verifying the authenticity of an item, or detecting leaks. Kids also use these ‘invisible pens’ to write secret notes to each other.
  • Tonic water. The quinine in Tonic Water is fluorescent while soda water is not. Some fancy bars may have black lights to highlight this effect.
  • Scorpions. Scorpions and some other insects are fluorescent. Thankfully I do not live in an area with Scorpions. But if I did I could imagine my wife ringing the house with UV lights to see the little monsters coming!
  • Whitening Agents. Laundry detergents, teeth whiteners, paper, and other items have whitening agents which are fluorescent.
  • Antifreeze. Manufacturers add fluorescent chemicals to antifreeze to enhance leak detection.UV_inspection
  • Bodily Fluids. Many bodily fluids such as urine, saliva, or semen glow under UV light. Although blood is commonly shown as being fluorescent in crime dramas, it generally doesn’t glow very well under UV light. It takes another agent such as Luminol to cause it to really pop.
  • Some Cosmetics. There are special cosmetics that are designed to glow under UV light, giving quite a show at some parties where the hosts have deployed blacklights to make things pop. However, there are normal cosmetics that may fluoresce without the wearer realizing it. This could be embarrassing in the wrong circumstances – like at those same parties!

UV Makeup

What Can a UV Light Be Used For

  • Detecting Leaks. Many industrial chemicals (such as antifreeze discussed above) are fluorescent, and leaks can be easily detected by a simple UV light. Fluorescent dyes can also be added to systems to detect difficult to find leaks.
  • Curing Resins. UV Resins, in combination with UV light, can cure at low temperatures and in half of the time of normal resin curing. This can add versatility to resin application since they will not cure without UV light.
  • Detecting Counterfeit Money. Many countries include watermarks or other markers in their currency that are detectable by a UV light. UV lights can be used to detect the absence of UV markers on currency, or the addition of inks or chemicals that should not be there.


  • Detecting Art Forgeries and Repairs. Paints, inks, dyes, and other materials have different levels of fluorescence, and these levels can change with age. A UV light can show differences within an art piece, highlighting areas that have different or changed characteristics than original. This can indicate a repair or restoration.
  • UV Pens. UV Pens are sometimes marketed as having ‘invisible ink’. There are a variety of different invisible inks that can be made at home, UV pens make use of the fluorescence in whitening agents or highlighters that are activated by UV light. This makes them great for kids to use in sending secret ‘spy’ messages. A UV pen can also be used to easily mark items for discreet identification.
  • Black Light Art. Artists can use fluorescent paints and dyes to make artwork that is meant to be seen under a black light. They can also be used to enhance visible light artwork, creating a duality or unseen quality to the art piece.
  • Black Light Makeup. If the nightclub or party you are going to has a few UV lights, plan for it and show a darker, or lighter side of yourself.
  • Crime Scene and Room Investigation. Many bodily fluids glow under a UV light (also sometimes referred to as an Alternate Light Source, or ALS). This helps investigators in piecing together what happened at a crime scene. These same techniques can also be used to inspect real estate for hidden pet stains and hotel rooms for cleanliness.
  • Event Admission (Hand Stamps). Attendees will appreciate having a hand stamp to allow admission into an event that is only visible under UV light. Being otherwise invisible, the stamp doesn’t have to be scrubbed off the next day. They are also much more difficult to forge or transfer to another person.
  • Arson and Bomb Investigation. UV lights are a valuable tool for investigators in determining the source of a fire, hydrocarbon residue, and even bomb fragments.
  • Non-Destructive Materials Testing (NDT). UV lights can be used as a tool to test infrastructure projects such as bridges and tunnels for structural integrity, reliability, and safety. Aircraft, auto, and marine industries also use UV lights for NDT.
  • Disinfecting and Sterilization. UV radiation damages biological tissues. Because of this, UV lights are can be used for sanitizing air, water, and surfaces very efficiently. UV sanitation systems are found in hospitals, hot tubs and aquariums, water treatment facilities, and even toothbrush cleaners. Berkley’s UV Tube project aims to have real impacts in developing nations where waterborne illnesses can be deadly.


UV lights, or blacklights, can show you things that were previously just hidden from view. Have some fun and carry one around with you to open up a new world that was right in front of you the whole time. Although you may not want to bring one to your hotel room. Sometimes ignorance is bliss.
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