Ultraviolet light and Day-Glo« Paint

Looks like you clicked on the virtual blacklight (also known as ultraviolet light).  I first discovered ultraviolet light when I was eight years old, back in 1961. That was at least three years before the Pranksters (Ken Babbs) discovered it. I first encountered it at a science fair that my father took me to and I thought it was one of the neatest discoveries I had ever made.

Trying to get my parents to get me one was not an easy matter. They thought that ultraviolet light was too dangerous for an eight year old kid to play around with. That summer, we went to California and my uncle had an ultraviolet light source. It was a four watt fluorescent tube that ran off of two 45-volt batteries in series (90 volts). Since the batteries were so expensive, we ran the unit off a power supply. Today, they have inverter circuits that can run fluorescent lamps on regular flashlight batteries, but this was not the case back then.

The unit must have been pretty old, because the fluorescent lamp did not have the usual bi-pin connections at the ends of the lamp, but instead was what they called the bayonet type. They did away with this type of connection to get rid of the exposed live parts. It was a black box with a chrome handle on the top and a button you pushed to start the lamp. The lamp was mounted at the bottom of the box. You can see this lamp in the photo below:

Picture of lamps

In the photo, the lamp at the top is a modern 4-watt hot cathode fluorescent blacklight. It is 6 inches long from pin ends, but the light emitting surface is only 4 1/2 inches. The tube below it is the one from my uncle's unit, which must be at least 50 years old. The very small blacklight at the bottom is the latest thing, a cold cathode fluorescent. Unlike the above lamps, it has only one connection at each end, rather than two.

We went to Disneyland that summer and found out that they had psychedelic rides that went through Day-Glo scenes illuminated by ultraviolet light. One of them was called Alice in Wonderland. They even had an ultraviolet store. I got a bottle of phosfluorescent paint that was made by some company in San Gabriel, California that my uncle said he drove past every day on the way to work and he said that the whole building glowed in the dark at night.

After we got back from California, my uncle gave me an ultraviolet kit, which included an argon-glow light source, three rocks that glowed, a bag of optical bleach, some invisible ink (which was optical bleach in water), four bottles of white liquid that turned different colors when exposed to ultraviolet light, some tracer powder, a glow in the dark crayon, various other items and a booklet of information and experiments. Edmund Scientific used to sell this kit with a different light source, but they don't seem to anymore. I don't know if the company that made the kits went belly up or what.

My uncle died in 1965, and I got his ultraviolet unit and it still works to this day, although I have outfitted it with an inverter circuit, so now it runs on regular batteries. Before the Hippie thing caught on, about the only way to get ultraviolet supplies was by mail order, although you could get fluorescent paint just about anywhere. When the Haight-Ashbury scene happened, the blacklight/Day-Glo thing became such a fad that you could buy the blacklight lamps just about anywhere. Today, you usually have to go somewhere like Spencer Gifts or a good sized hardware store to get one.

Day-Glo is a brand (a registered tradmark of the Day-Glo Color Corp.) of fluorescent paint that was around in the 60's, but I haven't seen that brand in my area lately, although they do have a web site (see below). It probably wouldn't have become a household word if it hadn't been for Tom Wolfe's book about Ken Kesey and the Pranksters. The kind I remember was oil based rather than water based. They may have also made water based Day-Glo too, but the kind I got in the mid-60's was oil based. The water based kind was usually used for body painting, which became another 60's fad. Although the fad has since died down, blacklights can still be found in most Hippie pads.

The actual chemicals used in optical bleach and fluorescent paint are kept a closely guarded secret. A good project for chemistry majors would be to run a chemical analysis and find out what these chemicals are. The fluorescent paint actually consists of several substances. First, there is the fluorescent chemical, which does not give off any color under normal light but glows under ultraviolet light. This chemical is different for each color of paint. Then, there is the transparent dye that gives off the color under normal light, but doesn't glow. Finally, there's the rest of the substances found in paint (the binder, the stuff that makes it stick).

Distinguishing between fluorescence and phosphorescence is also important. Fluorescent materials (like Day-Glo paint) only glow when excited by the ultraviolet light. Phosphorescent materials continue to glow after the light source is removed. These are what we call glow in the dark materials.

In case you're wondering what ultraviolet light was used for before the Hippie thing happened, it has many uses. First of all, I need to point out that there are two kinds: long wave and short wave. The long wave lamps were the ones that Hippies use and are generally considered harmless. The wavelength these lamps emit is 365 nanometers (a nanometer is 10-9 meters).

The short wave lamps are the ones that can harm you. The wavelength of these lamps is 253.7 nanometers. They include the suntan lamps, the lamps that erase E-PROMS, and the lamps that cure a certain kind of cement which they use to fix windshields and the cement the dentist uses to fix your teeth. That's why you should wear some kind of eye protection when you go to the dentist. It's not just the retina of the eye that can be damaged, by the way. It also causes the lens of the eye to become cloudy and that's what we call a cataract.

Short wave lamps are also used as germicidal lamps. In addition to being used in hospitals, I've seen them in bars where they wash the beer mugs. What they are is a fluorescent lamp with no phosphor coating (they're clear) and made of a special glass that doesn't filter out the short wave ultraviolet light. They produce about the same color as a mercury vapor street light, because that's what they are, mercury vapor, only low pressure rather than high pressure.

So how do ultraviolet lamps generate the 254 and 365 nanometers of light? This usually comes from a mercury vapor discharge, which generates both wavelengths. In addition to the invisible light, a mercury vapor discharge also emits three wavelengths of visible light at 436 (between violet and blue) 546 (green) and 578 nanometers (between green and yellow). This explains why the light emitted by an ultraviolet light is not completely invisible. Although most of the visible light is filtered out, it is impossible to filter all of it out without also filtering out the ultraviolet light, since 365 nanometers is very close to violet. To make a true blacklight, you would need a light source with a very narrow bandwidth, and so far, we don't have one.

The long wave lamps have many other uses besides making Hippies glow, but you wouldn't know that back in the 60's. They've been used in show business for quite some time, not only Disneyland, but also in skating rinks and in nightclubs. The unfiltered kind, which put out more visible light than the filtered lamps, have different kinds of applications where the additional light doesn't pose a problem. The main application I see them used for nowadays is for exposing blueprints and in bug zappers (I did a Lycos search using the keyword blacklight and although a few articles came back on Hippie posters, most of the articles were about bug zappers). Bugs can actually see ultraviolet light, but are almost blind to the yellow that is used in the lights designed not to attract bugs.

Ironically, blacklights are also used in the synthesis of LSD. I'm not sure how often they are used in a chemistry lab, but they seem to be useful when doing column chromatography. This is the process where you separate isomers and things like that. I never got to column chromatography in chemistry lab, so you'll have to ask some chemistry major about that.

If you're hard pressed for a blacklight (one place you can usually score one is Spencer Gifts), or you can make one using violet stage lighting gels, but the plastic material filters out some of the ultraviolet light. I covered an unfiltered blacklight with violet gel and found it puts out about half the ultraviolet light as a filtered blacklight. What works better is to get some ultraviolet filter glass. One of my bands did a gig in a club that had several blacklights made out of a mercury vapor street light in a fixture that had a filter glass lens. This put out a lot of ultraviolet light and the only disadvantage is these lamps take a long time (about 5 minutes) to reach full brightness when you turn them on, and if the power gets disrupted, it takes about 10 minutes to get them going again. The real advantage is the lamp cost. When you have to re-lamp them, it only costs about 15 dollars per lamp, and the lamps have a life of about 24,000 hours. Blacklights were only one aspect of a psychedelic light show, of course, to learn about the rest, check out the lightshow page.

On 3-31-98, I found that Home Depot was selling the 4-foot 40 watt blacklights for $10. They come in a pink sleeve that says blacklight on it. Here's some of the sizes that the fluorescent type of blacklights come in:

Lamp #: Watts: Length: Life (hours)
6 in.
9 in.
12 in.
18 in.
24 in.
48 in.

What those weird numbers mean:

The F means fluorescent, as you might have guessed. The number after that is the wattage of the lamp. The number after the T is the diameter of the lamp in 8ths of an inch. A T5 lamp has a diameter of 5/8ths of an inch. T8 is one inch and T12 is 1 and 1/2 inch. The BLB stands for filtered blacklight. Lamps that are marked BL are unfiltered blacklights. You can always tell these because they are white when turned off rather than black.

The larger the lamp, the longer the life. This ranges from about 6000 hours to 20,000 hours. The values in the chart are from the Westinghouse Large Lamp Catalog. They also come in U-bent models. I ran across a web site selling a U-bent version that comes with an adaptor that screws into a standard light socket.

Note to folks in other countries concerning the fluorescent type of blacklights. It's OK to buy the lamps from the United States, but not the fixtures, because the fixtures in the United States usually  run on 120 volts, not 240. As long if you use the fixtures designed for your country's voltage, the lamps will work just fine. This is not true of other types of lamps, where you need to match the lamp voltage to your mains supply.

Although the fluorescent type of ultraviolet  lamps are the most common found, there are other types. Another type is the argon lamp, although not as popular as it once was. This is the type of lamp that is used for most colors of "neon" signs. Only the orange signs actually contain neon gas. All the other colors are argon lamps that contain a phosphor coating that gives off the color of the lamp when excited by the ultraviolet light that the argon gas produces. They used to make little tiny argon indicator lamps (about the size of a NE-2 neon lamp with wire lead connections) and any time you see a green "neon" indicator light, it is actually an argon lamp with a phosphor coating that glows green. Like neon signs, they could make these small argon indicator lights every color of the rainbow with the various phosphor coatings they use for the "neon" signs, and they would make great miniature Christmas lights, since they run on line voltage (with a series resistor for each lamp), which means parallel light strings rather than series ones. It's a shame nobody has marketed that idea.   

The most exciting new development in ultraviolet lamps is the ultraviolet light emitting diode. Like regular LEDs, they are solid state, not hollow glass, which means they are very rugged. They also have a 100,000 hour life and only require 4 volts at 20mA to operate. I have found that the easiest way to get one so far is to buy an ultraviolet keyring light, which costs about $10, such this one, once sold by the Electronics Goldmine, which is where I got mine. I have not been able to find places selling the just the UV LEDs at a reasonable cost. Radio Shack doesn't sell them yet, but when they do, all sorts of wonderful things can be made, such as ultraviolet Christmas light strings and even ultraviolet chaser lights. Just think what that would add to a Rave gathering.

UV keychain light

Some ultraviolet related web sites

Copyright © 1995-2002, Colin Pringle (colin@wild-bohemian.com)
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