You’ve probably seen black lights being used in movies and heard about some of their uses. It’s time to learn more about them – what they really are, how they work, their usage in everyday life, and where to buy them in this complete guide!
What is black light?
A black light – or also spelled “blacklight” – is a light that emits… no, not ‘black’ light, but ultraviolet light, which is why some people call them as such.
People also call them ‘Wood’s Lamps’ in honor of the inventor of the glass UV filter, Robert Williams Wood. By definition, a black light’s light should be in the UV (ultraviolet) range of the spectrum, and very little ‘visible’ light should be, well, visible.
What is ultraviolet light as it relates to black light?
The light spectrum contains the range of colors of the rainbow (and more). At one end, you have red-colored light and, at the other end, you have blue-colored light. All of the visible light in the world (for humans, at least) falls within those two colors. The reason that they do is that they all have wavelengths that can be picked up by the human eye.
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At the blue end of the spectrum, the light has a shorter wavelength, and at the red end of the spectrum, the red light has longer wavelengths. If you go any farther in any direction, you get light that is there, but that we cannot see.
On the red end, you move into infrared light, the kind of light that is used in remote controls, and at the other end of the spectrum, you step into a type of light whose wavelength is too short to also be seen: ultraviolet light.
Why is it called “black light” then?
Though you may not see it, black lights do emit light — and a lot of it, too. They emit ultraviolet light, or UV light, a type of light not visible to us but that many animals can see.
When a black light bulb is on, it looks as if only blackness is being emitted. If you were to use a black light as the primary source of light in a dark room, you would be left in complete darkness. It is pretty cool to think that light is being emitted but we cannot see any of it, nor does it light up the room in any way.
Some black lights will also emit violet light as a visual confirmation that the light is on and working.
How does black light work?
Black light emits ultraviolet light, a type of electromagnetic radiation. There is little difference between this type of light and any other kind of light, such as the one produced by an incandescent bulb, except that the wavelength of ultraviolet light falls outside man’s visible spectrum. It is there; we just cannot see or perceive it.
However, there is a way that we can ‘kind of’ see ultraviolet light. With special filters or coatings that absorb or block some of the light while allowing only UV-A (but not UVB) and a little visible light to pass through, you’ll be able to see the faint, purplish glow produced by bulbs.
Some things glow brightly, however, and this is due to compounds known as phosphors. When UV light hits objects with phosphors, these compounds will glow. You can find phosphors in tonic water, tooth whiteners, antifreeze, some minerals, bodily fluids, banknotes, detergents, among others, so if you shine a black light on any of those things, they glow and become visible.
What are some uses of black light?
There are many uses for black lights, and here are just a few of them:
Counterfeit detection
Some countries fraud-proof their currencies using black light technology, which can help detect fakes. Of course, well-made fakes may escape detection, so UV should not be the only method to separate fake currency.
Forensics
Human bodily fluids, such as urine, semen, and blood can all show up under a black light, and this can be used by forensic teams to detect bodily fluids and to also paint a picture of how they were expelled from the body.
Detection of stains
Black lights will show bodily fluids, such as saliva, semen, urine, and blood. UV lights can also show laundry detergent stains, and this is why your clothes light up under UV light.
Anything with quinine will show up under UV light, including club soda and tonic water. Ink made from lemon juice and toothpaste or teeth whiteners will also have the same effect.
Cleaning with black lights
As gross as it is, black lights also help cleaners, especially those in hotels, to detect the same bodily fluids, as well as pet stains when they are cleaning.
Handstamps
When you leave an event or venue, security will often stamp your hand with the event’s logo, and the stamp only shows up under UV light. This is how you gain re-entry. If the UV lamp is turned off when you try to look at the stamp, you won’t see anything.
There are many more uses for black lights, but these are some of the most common ones.
The fun stuff: black light tattoos and black light paint
You know of tattoos, but have you heard about black light tattoos? These are becoming more and more popular these days.
These tattoos typically hide messages, words, and images when viewed using, say, incandescent bulbs and only become visible under black lights.
Ultraviolet-reactive ink is used to create either the entire tattoo or parts of it, and these parts are invisible to the naked eye, just like a message written on paper with invisible ink. When the tattoos are placed under a blacklight, the hidden sections become visible. Turn it off, and the tattoo subsequently disappears.
Just like black light tattoos, black light paint uses UV-reactive paint to hide in plain sight. When exposed to ultraviolet light, the paint is exposed to reveal the hidden image, words, or message. However, black light paint should not be confused with glow-in-the-dark paint, which is paint that becomes fluorescent when it is dark.
Now that you know, is it time to celebrate with a black light party? But wait — you’re probably wondering — what are its effects, if any, on people?
Is black light safe?
When we think of ultraviolet light, we think of the harmful UV light that comes from the sun. We will probably start to think about how UV light is used in tanning beds, and that takes us full-circle to black lights and the UV light that they emit. So, the question is, are black lights safe, and should we be worried about our safety?
While both the sun and black lights emit UV light, there is a vast difference in the wavelengths of light. The ultraviolet rays of black lights have a longer wavelength than ultraviolet rays of the sun, which makes them closer to visible light on the ultraviolet spectrum.
Because of this, short-term exposure to the ultraviolet rays of black light is no different than short-term exposure to other kinds of visible light. The long-term effects, however, are not yet known. Some wavelengths of ultraviolet light can be harmful, and if safety is a concern, we do not recommend prolonged exposure to black light.
But maybe, just maybe — a black light party won’t be too bad, don’t you think…?
Our picks for the best black light
There are many types of black lights out there, and they are not confined to only lamps.
For your next party, you can buy an arsenal of individual light bulbs, flashlights, floodlights, and more. Let’s take a look at some of the most popular options.
Best Black Light Bulb
- Lunsy UV LED Light Bulb
These light bulbs are affordable and long-lasting. They are LED bulbs and last a lot longer than fluorescent or incandescent bulbs, cutting down on your electricity bill, and emitting as much ultraviolet as any other bulb.
They can be used for a variety of purposes, including parties, as decoration, in aquatic tanks, for body art, and more.
The best thing about them is how affordable they are. Buy them and use them for up to 25,000 hours.
Best Black Light Flashlight
- UV LED Flashlight 2 in 1 UV Black Lights
This 2-in-1 flashlight can be used as a UV blacklight and a regular flashlight, giving you limitless applications. It is perfect for detecting stains that are not visible to the human eye, allowing you to better clean a room, track an animal, or check for pet stains.
There are 4 modes, a wide-to-narrow beam zoom, and a high-lumen LED bulb that can hit objects up to 200 meters away. With IPX4 water resistance, you can even use it out in the rain.
A great flashlight to always have on your person.
Best Black Light Strip Light
- UV LED Black Lights Strip Light with 300 LEDs
With 300 LEDs spread over 16.4 feet, this is a great addition to any party, celebration, or event. This light option is the standard one, but you can opt for longer lights if you need them, dimmable lights, and waterproof lights for all of your outdoor events.
The lights run on mains power, but you can convert to battery power if needed. The high-quality LED bulbs last a long time and will not fade over time, giving you the same light on the last day as you got on the first day.
Easy to install and use, these lights are going to elevate your next event or party to another level.
Best Black Light Flood Light
- 100W UV LED Flood Light
With 100W of power, you are not going to be left in the dark with this light, or maybe you are…anyway, you have 50,000 hours of life, high efficiency, and you can operate the light in temperatures as low as -20C and as high as +50C.
The instant-on feature means that you are good to go as soon as you power it up, and the 120-degree beam angle helps you hit a generous area with the light. The output is uniform and consistent, with no glare or hotspots.
If your thinking of a big party or event and you need to cover a large area with your black light, this is well worth the investment.
Best Black Light Strobe Light
- UV Par Stage Light
Looking for a stage light for your next event? This 18-bulb LED light is just the thing. It is extremely durable, compact and lightweight, and has a remote control for wireless operation. There are multiple modes, including sound activation, and the speed is fully adjustable.
Enhance a wedding, birthday party, gender reveal, and more with this strobe UV light.
Best Bug Zapper Black Light
- Aspectek Electronic Insect Zapper
We already mentioned that other creatures can see ultraviolet light and that makes a black light perfect for helping to catch bugs. This black light uses fluorescent tubes and will help to rid you of flies, moths, mosquitoes, wasps, cockroaches, and more.
The fluorescent tubes’ UV light attracts the bugs, and they are zapped and humanely killed by the high-voltage on contact, while the mesh screen protects you and any loved ones from being accidentally zapped.
Keep your home chemical- and trap-free with this effective UV bug zapper. (Don’t try to test the zapper yourself, though, as it can cause a nasty surprise for you, too.)
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What to look for when buying black light
Before you go out and buy a black light, there are some things to think about.
Old vs. new black light technology
Fluorescent and BLB black lights used to be your only option, but LEDs have made a big impact on the market. So, which should you go for?
Fluorescent and BLB lights can often be relatively cheaper, but we believe that the benefits of blacklight LEDs far outweigh the cost.
LED bulbs are more efficient than their fluorescent tube counterparts, and that means that they do not cost as much to run. They can last for more than 25,000 hours without quickly burning out as fluorescent tubes do, and they do not use as much power, too. Over time, a more expensive LED bulb can save you money.
Since LED bulbs have a longer lifespan, you also do not need to buy as many replacement bulbs, saving you even more money. Even better, these bulbs do not contain any of the hazardous materials that fluorescent bulbs can. If they break, they are easy and safe to clean up.
LED bulbs are the clear winner in our books.
Black light – too much or too little?
Although you won’t see the light, you still need to know how much UV light you need. Lumen is the unit used to measure visible light, and this measurement is useless for UV light. It is better to measure black light (or rather, black light bulbs) by its wattage.
Simply put, you will need 1 watt of UV energy to cover 100 square feet, and you can double that number for every extra 100 sq. ft. When you buy black light bulbs, check their wattage and take 5% of that to get the UV wattage. The number you get is the wattage you will use to make sure you have enough to cover a designated area.
Which of the black lights options should I buy?
The type of black light that you need will depend on what you are going to use it for.
If you want to use UV light to illuminate a large area, look for a floodlight, but if you want something portable to check for stains, then a flashlight is going to be better. You’ll be better off if you first decide based on your intended use, and then buying the light and bulbs.
This page last updated May 5, 2023