Is a Blacklight a UV Light? 365 nm vs 395 nm Explained
Our customer asked:
Is a blacklight the same thing as a UV light, and does 365 nm vs 395 nm really matter?
TL;DR
Yes, a blacklight is a UV light. "Blacklight" is the everyday name for a lamp that emits UV-A, the longest and lowest-energy band of ultraviolet (315 to 400 nm). Every blacklight flashlight is a UV flashlight. The reverse is not true: UV-C germicidal lamps are UV lights, and they are not blacklights. They belong in a sealed sanitizer. You should never hold one in your hand.
So what does a blacklight flashlight do? It emits UV-A, which makes fluorescent materials glow in visible colors. You use that glow to find or verify things. The question that matters when you shop is which wavelength you are buying, not whether to call it a blacklight or a UV light. That number decides what you will be able to see.
I run product innovation at LUXPRO. Part of my job is choosing LEDs. Here is how this looks from the side of the table where we pick the parts.
The three kinds of UV, and which one is in a flashlight
| Band | Wavelength | Where you meet it | In a handheld flashlight? |
|---|---|---|---|
| UV-A | 315 to 400 nm | Sunlight, blacklights, nail lamps | Yes. This is every consumer UV flashlight. |
| UV-B | 280 to 315 nm | Sunburn, reptile lamps | No. |
| UV-C | 100 to 280 nm | Germicidal lamps, water treatment | No, and it should not be. |
You may read elsewhere that UV flashlights emit "a mix of UV-A and UV-B." They do not. The LEDs used in detection flashlights emit a narrow band, typically about 10 to 15 nm wide, centered in UV-A. If someone sold a handheld light that put out meaningful UV-B, I would not want it in my house.
365 nm vs 395 nm: the practical difference
Consumer UV LEDs come in two families.
365 nm sits deeper in the UV. Your eye barely sees it, so the beam looks like a faint gray-white. Because so little visible light washes out the scene, fluorescence shows up with high contrast. Many materials also absorb better at 365, so they glow harder. Drawbacks: the LEDs cost several times more, they produce less output per dollar, and to get the full benefit you need a black filter glass (often sold as ZWB2) over the lens to strip the leftover visible light. That filter adds cost and absorbs some output.
385 to 395 nm sits at the edge of visible violet. You can see the beam as purple. These LEDs are efficient, inexpensive and sturdy, which is why most UV flashlights under $30 use them. The drawback is that the purple light reflects off everything, so faint fluorescence on a light-colored surface has less contrast than it would under 365.
| Job | 385 to 395 nm | Filtered 365 nm |
|---|---|---|
| Scorpions | Excellent | Excellent |
| Uranium glass | Excellent | Excellent |
| Charging glow tackle and markers | Excellent | Good |
| AC and automotive leak dye | Very good (most dyes are tuned for this range) | Good |
| Dried pet urine | Good in a fully dark room | Better contrast, especially on light carpet |
| US currency thread | Good | Better |
| Driver's license and passport inks | Some features show, some do not | Best |
| Manganese glass, many minerals | Weak or none | Best a flashlight can do |
Where the LUXPRO LP32UV sits, and why
Our LP32UV is specified at 385 to 390 nm. We print that number on the product page. Many inexpensive UV lights say only "UV" or "395" and then ship LEDs that drift toward 400 to 405 nm, which is visible violet and barely UV at all. That is the biggest quality problem in this category. It is also why two lights that look identical online can perform very differently on the same stain. The shorter end of this family excites more materials, so a true 385 to 390 outperforms a 400-plus light that calls itself 395.
Why not 365? It comes down to what the light is for. The people who buy the LP32UV are checking carpets, hunting scorpions, testing glass at an antique mall, and charging lures on a boat. For those jobs, beam width matters more than spectral purity. Thirty-two emitters across a wide head give a broad, even flood that covers a lot of floor on each pass. Building that same flood from filtered 365 nm emitters would take this from a $16.99 light you keep in a drawer to a specialist tool that costs several times more. For most households that is the wrong trade.
It is the right trade for some people. If you inspect IDs for a living, collect fluorescent minerals, or do dye tracing in bright shops, buy a filtered 365. I name the specific models I would choose, none of them ours, in my 7 Best UV Flashlights review.
How to tell what wavelength a cheap UV light really is
- Look at the beam on a white wall. Strong, saturated purple with a bright center means it is likely 400 nm or higher. A dimmer violet is closer to a true 385 to 395. A faint gray-white is 365.
- Shine it on a US $20 bill. The security thread should glow green. If you get only purple glare and no thread, the light is probably not producing UV.
- Check for a stated range. A maker who knows the number will print it. "UV" with no number tells you nothing.
Where else do you find ultraviolet light?
The sun is by far the biggest source. About 95 percent of the UV that reaches the ground is UV-A, the same band as a blacklight. You also find it in tanning beds, nail-curing lamps, bug zappers, aquarium and reptile lamps, welding arcs, and the UV-C lamps inside water purifiers and HVAC sanitizers. A blacklight flashlight is one of the lowest-power sources on that list.
Frequently Asked Questions
Q: What does a blacklight flashlight do?
It emits UV-A light that makes fluorescent materials glow, so you can find stains, pests, leaks and security features that are invisible in normal light. Full list: What is a black light flashlight used for?
Q: Is 395 nm "real" UV?
Yes. UV-A runs up to 400 nm. A true 385 to 395 nm LED is ultraviolet. The problem is lights sold as 395 that measure 405, which is visible violet.
Q: Will a blacklight flashlight kill germs?
No. That requires UV-C, which is a different band and is not safe in a handheld light.
Q: Is UV-A safe?
It is the mildest UV band, and flashlight power levels are low, but you should never look into the beam. More here: Are UV flashlights safe?