(4)
Your tool for this guide: a blacklight
Blacklight = UVA = longwave UV = 320-400 nm
Along with discussing all kinds of ultraviolet and their uses,
this book shows you how to use a black light, also known as a
longwave UV or UVA light. This chapter is about how to buy the
correct kind of black light.
As discussed in the previous chapter, there are different
kinds of ultraviolet light. The most common kinds are UVA, UVB
and UVC. The type of ultraviolet light you want to purchase for
this book is the UVA, or longwave ultraviolet light. These are
commonly marketed and referred to by the nickname, blacklight.
There are different kinds of ultraviolet lights which you should
not buy for purposes of this book. Do not buy shortwave, UVB
or UVC. UVC lights are most commonly marketed for germicidal
purposes.
Luckily, the longwave ultraviolet light or black light is
the most common and inexpensive ultraviolet light on the market.
Buying your blacklight
There are many places to buy a good blacklight. You can pick
up cheap examples from amazon.com and ebay.com. Some science,
hobby and rock shops sell them.
Blacklights come in many styles and powers. This includes
screw in bulbs and large and small flashlights. I own a small
flashlight style and a screw in bulb. Both were inexpensive and
serve different purposes. The bulb screws into a standard light
socket and the flashlight can carried around in my pocket.
As long as the light gives off black light, the style is up
to you.
The above little flashlight is good for authenticating
art, currency and such. They take batteries and can be carried
around most anywhere. This is the most popular style for collectors.
The above pocket sized LED and other high
powered balck lights are good for rock hunting and general inspection,
and are also good for examining art, collectibles and currency.
It uses batteries, so you can take it anywhere.
Screw in black light light bulbs like the
above are especially good for art and crafts displays like posters,
paintings and clothes. This type of light can also work well
for inspecting art, but is not as portible as the above flashlights.
As you can see, they look a regular scew in visible light fluorescent
light bulb except the bulb is black not white.
Be careful when purchasing screw in black lights, as many
are not ultracvioleght. Make sure it specifically mentions that
it is UV or makes things glow in the dark. Most UV lightbulbs
are fluorescencet. Many incandescent 'black light' bulbs are
not ultraviolet. The non-UV incandescent lightbulbs are cheap,
so if you pick the wrong one you won't be throwing away lots
of money.
As you want to stick to only UVA blacklight, names for lights
you want to avoid include:
UVC
Shortwave ultraviolet
Germicidal
How to use your blacklight
Once it's plugged in or the batteries popped in, most blacklights
are as easy to use as normal flashlights. The blacklight only
works in the dark, the darker the better. They can work outside
at night and inside in a dark room. You should stay in the dark
for at least a couple of minutes so your eyes get adjusted to
the dark. After that, shine the blacklight around and you should
find things that some things fluoresce, meaning they glow the
in dark. Most black lights emit a small amount of visiable light
so that you know it's on.
When you are later examining specific objects-- like a photo
card or dollar bill-- it's best to examine a material against
something that does not fluoresce. If the background gives off
light it may effect the results.
Safety of blacklight
You'll be happy to know that UVA or blacklight is the safest
type of the ultraviolet light. The light you will use is just
longer in frequency than visible light. In fact, regular sunlight
contains UVA light, so you're exposed to it on a daily basis.
It is UVC, or shortwave, that is more dangerous and extra care
is to be taken.
While blacklight is not of great danger, reasonable care should
still be taken. The keys with blacklight is to not stare directly
at the light source, just as you shouldn't stare directly at
the sun or a regular light bulb. And, as with sunlight, don't
everdo exposure. Don't try and suntan with your black light.
If you want, you can wear a strong UVA/UVB protectat suntan lotion,
just as you should be wearing outside in the sunlight.
Test your blacklight around the house
In the dark, go around your home or office and see which things
fluoresce and which do not. Common around the house things that
fluoresce include:
White paper
Some cloth, incouding parts of shirts, hats.
Laundry detergent
Eyeglasses
Tennis balls
Some glass and plastics
Some things will fluoresce so brightly you can almost read
by it!
Vaseline under black light
laundry detergent in tub
white sewing thread on spool
Next: Where does
ultraviolet come from? How does it make stuff fluoresce? Why
can't humans see UV light?
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