From Mensagenda — June 2006

You might not realize it, but you could be holding a science experiment in your hands.

Some months back I was looking at my Mensagenda when I noticed that it was a glowing pink color. This surprised me no end. It wasn’t the color that surprised me. That color had been used many times in the past. What surprised me was that I could see it.

This was all under a blue light, a fairly pure blue light from an LED lamp that I made myself. Under this light, red things look brown and green things look green, sometimes. Everything else looks blue. But this cover came out a bright pink, as bright as if it were under a white light.

Then I remembered that this kind of color is sometimes called fluorescent. It didn’t just look like it was glowing. It really was glowing.

I grabbed a bunch of other Mensagenda back issues with fluorescent colors, pink, orange, yellow, green, and blue. The yellow was bright yellow under the blue light. Oddly, the green cover glowed yellow. The orange cover came out pink. The blue was — surprise! — blue.

I checked the same covers under a red LED light. Nothing but red and black. There was something about the blue light.

Fluorescent light tubes work when you pass an electrical current through a gas. The electricity stimulates the gas, which starts to glow. Fluorescent dyes work the same way, although the setup is different. The dye that is, say, yellow, will reflect yellow light and absorb all other colors. Yellow fluorescent dye absorbs light, which simulates its molecules to glow with yellow light. That’s why fluorescent colors are so bright. In their own way, they are light sources.

That explains an odd phenomenon that my brother once noticed. He has one of those green lasers used in amateur astronomy. These are the most powerful lasers allowed for civilian use and made the news recently when some hooligans tried to use them to blind pilots. Tom’s heart is pure, I assure you, and he uses it only for its proper purpose. Except, of course, when he’s goofing off around the house.

Light from a laser is pure color. The light from a green laser is nothing but green. Shine it on a blue wall and it reflects back green. Shine it on a red carpet and it reflects back green. Shine it on orange hunting clothes and it comes back … yellow?

There are two possibilities here. It could be that the blaze orange clothes fluoresce yellow. Or maybe it reflects a little green and fluoresces pink. In the world of colored lights, green plus pink equals yellow.

One thing had me wondering. An LED is often a form of fluorescent light. The electronic component gives off light, often ultraviolet, which in turn causes fluorescent material to give off light in whatever color it is supposed to. Could it be that my LEDs were also giving off UV?

For this I got out my UV detectors, which the average person would recognize as glow-in-the-dark toys in various colors. First the blue LED light. The toys glowed in color, indicating some UV, although not as much as you would get from a good blacklight bulb. The red LED just made things red. No UV here. It probably uses a different type of luminescence. Tom’s laser was not available for testing.

Recently I came across some brightly colored taffy in a candy store. The intensity of color seemed about right, so I bought a quarter-pound for home testing. Nothing but blue, green, and brown.

As I ate my experiment, I was assured that I could not glow internally. But not everyone is so sure. Recently genetic engineers created a pig that glows in the dark. A lot of people wondered who would want to find a pig in the dark. Any farmer who thought he was raising Hampshires and Chester Whites, but was really raising Houdinis, that’s who.

That would be some expensive bacon, though. These pigs are really bred for biomedical research. Making something glow under a microscope is a great way to study biological samples. The problem is, most fluorescent dyes kill cells. One exception is green fluorescent protein. Tissue dyed with GFP will continue to chug away as though nothing was up, all the while lighting up the night, or at least a microscope slide. If the sample already comes with GFP, all the better. It saves preparation time.

As for me, further research will require the purchasing of equipment with actual readouts on them. Don’t hold your breath.