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

Ultraviolet light in Science, Industry and Technology

The following are examples of how ultraviolet light is used in advanced areas. Many to most of these examples use ultraviolet light beyond the longwave in your black light, but are interesting to know about.



Irradiation, Purification and Sterilization (Uses UVC)
UVC light, typically at 254 nanometers, is used to irradiate, purify and sterilize water, air, food, sewage, laboratories, office buildings, pools and aquariums. Industrially the process is called Ultraviolet Germicidal Irradiation (UVGI).
Direct and long enough exposure to UVC light can kill, amongst other things, Anthrax, Typhoid, E. Coli, Tuberculosis, Salmonella, Dysentery, Staph Infection , Strep, Legionnaire's Disease , Cholera , Influenza, Hepatitis, Algae, Fungi. The UVC breaks down the molecular bonds of the organisms, making them unable to reproduce.

There are limitations to UVC as a germicide. There must be direct exposure to the light for it to work. This means in a lab or building there may be areas that are missed. Because of this, laboratories often used UVC in combination with other methods.

UVC is commonly used to purify circulating air, such as in an office building. While the air is purified at the spot of exposure, the air can get dirty again with circulation.
There are commercially marketed hand held UVC germicidal lights for normal people. They are commonly used by travelers to sanitize hotel and airplane bathrooms, beds, dishes, etc. I've even seen a UVC toothbrush cleaner.

While one should take due care using UVC light, there are advantages of UVC over other traditional disinfectant and purification methods. UVC doesn't effect they ozone, there are no dangerous fumes like with bleach and ammonia, and runoff won't contaminate lakes and rivers.

UVA offers about no practical purification, cleaning effect. UVB offers some. As regular sunlight includes UVB, it does have some disinfecting effects-such as when hanging wet clothes or exposing plates to sun on a camping trip. The drying out is also helpful.



Medicine (UVA & UVB)
Sunlight can cause health problems-- skin cancer, eye problems, etc--, but light therapy, using UVA and UVB, is used tor treatment of a number of dermatology conditions, including psoriasis and eczema. Veterinarians use ultraviolet light to identify ringworm in pets.

Danish physician Niels Finsen (1860-1904) won the 1903 Nobel Prize for Medicine for studies of how ultraviolet light could treat diseases, including Tuberculosis.




Identifying Gems (Uses UVA & UVC)
There are a variety of methods used to identify diamonds, rubies and other gems. This includes the use of UVA and UVC light. Gems fluoresce specific colors and brightness under the two lights. Sometimes a gem fluoresces one color under UVA and another under UVC. Other tests used include testing hardness, visual light color and appearance and place of origin.






Ultraviolet astronomy (all ranges of UV)
Ultraviolet astronomy is a part of astronomy that observes and studies the ultraviolet light given off by stars, planets, galaxies and the cosmos. As much of this light is beyond UVA and UVB and is blocked by the earth's atmosphere, the light can only be obseved from space or the upper atmosphere. UV telescopes are carried by rockets, the Hubble Space Station and the Space Shuttle. From the UV light, scientists can deduce the chemical makeup, weight, temperatures and even age of cosmic bodies.




WWII airplane safety (UVA)
During World War II, airplanes used maps written in UV fluorescent ink. During dangerous battle situations, the navigator could read the map without illuminating the cockpit.




Pest control (UVA)
Ultraviolet fly traps, or bug lights, are used to kill flying insects. The bugs are attracted to the UV light and trapped or killed with electrical shock.

(c) david rudd cycleback, all rights reserved