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Ultraviolet Light and Black Light: a beginner's guide
by David Rudd Cycleback


1) Introduction

2) What is ultraviolet light?

3) The different kinds of UV light

4) Your tool for this guide: a black light

5) Where does ultraviolet light come from? How was it discovered? Why can't we see it?

6) How are black lights made?

7) Practical and interesting uses for your black light

8) Examining art and collectibles: Introduction

9) Identifying modern fakes of antique paper memorabilia

10) Identifying counterfeit US currency

11) Identifying alterations to art, collectibles

12) Examining cloth

13) Examining art glass

14) Making glow in the dark art and crafts

15) Protecting yourself from the Sun's UV

16) UV light in science and industry

 

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(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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