Thread: Blacklights - Why some work and why some do not

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As part of my job at Glow Inc, I did a bunch of testing of black lights. What we found was that many blacklights, especially those made with round incandescent bulbs and LEDs are not actually UV lights (365 nm), but are purple lights (400 nm).

True 365nm UV lights make phosphorescent (glow in the dark) and fluorescent paint glow brightly with very little visible light.

400 nm purple lights look brighter, but are very inefficient as "black lights".

I wrote an article talking about every type of black light I could find, which you can read here:

http://glowinc.com/glow-in-the-dark/black-light.aspx

Good article with pics!

Those fake incandescent "blacklight" bulbs that start showing up during this time of year are not just crap, they are dangerous! They get super hot and can melt fixtures and worse...

If it costs under $5, then it is probably not a real blacklight.

Hehe, here is actually a funny story for you about cheapie black lights. We buy and use a lot of them around our shop. We would typically spend about $40 on nicer units. At some point, CVS had an after-halloween sale. They had these black light wands for $4. We didn't know how we were going to use them, but figured we couldn't pass up the price. Well, they were simple, compact, light weight, and did great for 2' black light. As a result, they became the preferred black light we used in the shop.

In fact, the last of them just got mounted into my barrel monster prop I am refurbishing.

But yes, most inexpensive black lights are absolute junk. However, most LED black lights, even expensive ones, are typically not very good either. Stick to tube-style black lights.

Skylighter, great article. What, if any CFL bulbs would you recommend? I need to do things on the cheap for now but your blacklight fixture sounds fantastic. Also, I found 2" round woods glass on the net for about $9 would this work as a lens on some UV leds and possibly provide good "short throw" results? Thanks for any help, Keith

On the cheap, I would HIGHLY recommend you just use regular black light tubes. They are readily available at Home Depot, Walmart for about $20.

Most LED "black lights" are 400 nm with almost no 365 nm output. If you put them behind woods glass, nothing is going to pass through.

As for CFL bulbs that were not coated, I only found one. We are getting ready to release the fixture/CFL combo from Glow Inc. at about $200. While, it is as nice as it comes, it is way overkill for most home haunters.

The haunted house we sponsor uses 4 4-foot double bulb fixtures with T-8 bulbs. They were available at Walmart at Halloween about a decade ago. Total cost each was $20 each. We have been using them for about 10 years without problem.

Danny

Cool, thanks for the info. you have saved me some money. I admit I was getting frustrated trying to find LEDs in the 365 nm range..... Thanks again, Keith

Thanks for the info as an amateur I was going to just get the cheap walmart bulbs

Its been mentioned before but just in case- here is the walmart casing- http://www.walmart.com/ip/Black-Light/8198021 for $20 though Ive seen the replacement bulbs for these units sold there for $10.