Have you ever wondered what a black light is? Did you ever figure out why the fluorescent poster glow in the dark?
You may probably see black lights at amusement parks or Halloween displays in the theater. Black lights look same as fluorescent lamps or incandescent light bulbs, however, they’re totally different. So what is really black light?
Trust me, you should be surprised. Last week, I was invited by a friend to a wonderful party. That was the best party I had ever. Everything was fabulously glowing in the dark. All amazing colorful! This inspired me to start our own glow party for our little princess’s 7th birthday.
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What is black light?
A black light also referred to as a UV-A light (ultraviolet light) or Wood’s lamp is a source of electromagnetic radiation that emits near-ultraviolet light, usually in 350-370 nano meter wavelength range, the invisible light to human beings eyes.
Our eyes can see visible light in a spectrum ranging from red to violet, including red, orange, yellow, green, blue and violet. And above violet light is ultraviolet light, including three models, UV-A, UV-B and UV-C. Both UV-B and UV-C are much more harmful when we look at the lighting directly.
There’re two types of black light in the market. One is BBL (stands for blacklight blue) lamp, and the other is BL (stands for blacklight) lamp, which is mostly used in bug zapper. And blacklight sources can be specially designed fluorescent lamps, mercury-vapor lamps, light-emitting-diodes (LED), lasers or incandescent lamps.
For BBL lamp, it has violet filter material on the bulb or in the glass filter in the lamp housing. This blocks most visible light and allow through UV. For example, a black light fluorescent tube, it glows in purple, but is not the UV light itself glows (UV light is invisible by human beings), is the visible light that escapes being filtered out by the filter material in the glass housing.
BL lamp has no filter material and produces more visible light and has blue color when working. This is used in bug zapper to attract insect. You can put a BL lamp near you in the yard or camping at summer night. It helps a lot to keep you and your family away from most flying insects, like mosquito, biting flies, and other insects.
Fluorescent black light is the most common lamp over the past years. With the development of lighting industrial, eco-friendly energy saving and long lasting life, as well as stable performance, LED (light-emitting diodes) black lights are starting to emerge. Some LED can produce ultraviolet light, but lowest energy UV photons can emit, usually ranges from wavelength 385-400nm. LED black lights are specially applied in stage and nightclub lighting.
Why black lights make objects glow?
What we see glowing under a black light, whether it’s on a newly white T-shirt or fluorescent poster, that material was named phosphor. The reason why most fluorescent lighting is visible, while black light is not, is the phosphors that coated outside of the fluorescent bulb.
A phosphor is any substance that emits visible light when some sort of radiation reflects on it. It turns out to visible light when converts the energy in the UV radiation, and let humans see it.
Any surface covers phosphor can glow in the dark when UV light shines, no matter they’re blackligts arts and crafts, cosmetics, party supplies, and blacklight glow runs or neon painting.
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How black lights work?
Black lights have phosphors coating on the bulb. When hit with photons, both heat and light are created. The phosphor coating absorbs the topper spectrum UV light, and lets the UV-A waves get through. When UV-A light shines on the objects with phosphors in the dark, they start to glow.
Under a UV light, white clothes, blacklight poster, cosmetics and party supplies that contain phosphors glow in the dark, and many fluorescent colored items emit a bright glow.
Which things glow under a black light or ultraviolet light?
There are many daily materials that glow when under a black light. The reason is that all these substances contain fluorescent molecules, also called phosphors. Fluorescent molecules have tendency to have rigid structures and delocalized electrons.
When you open a black light in the dark room, you would notice that there are phosphors all over the place. Teeth and fingernails contain phosphors naturally, among other things. The television screens, paintings, cosmetics and fabric may all have phosphors coating.
A newly white T-shirt is the most common glowing under a blacklight. Many laundry detergents also contain phosphors to brighten your white clothes with optical brighteners.
Clubs and amusement parks usually use black light paint or black light ink to light up in different pretty colors, also, used as event tickets when show up under a black light, and bank notes to help detect counterfeits.
Using a UV light or black light is the best way to detect scorpion. Some species of scorpion glow when exposed to ultraviolet light at night. You can check to see whether there’s scorpion or not when using a black light.
What is a black light used for?
Black lights are ideally perfect for family night, birthday, housewarming party, Halloween holiday decorations, Christmas party, and also up-lighting for wedding, stage floor, Bar, Night Club, Disco, DJ, Live Show, art studio, black light performance, rooftop party, glow party, outdoor fluorescent painted yard ornament, outdoor art installation, black light dance performance, screen printing emulsion exposure light, to inspect glue squeeze out on wood doors.
In addition to entertainment value, black lights have been put to use in mechanical engineering and repair, criminal investigation, forgery detection, and many other fields. Phosphorous dyes added to liquids will leak from the same places that the liquid itself leaks from, thus creating a phosphorous stain at any leak point. This is very easily detected with a black light. Airplane fuel lines and automotive air conditioner lines are two applications where this method is used extensively. Also, many bodily fluids (such as blood, semen, urine, and saliva) are phosphor-rich. Criminal investigators have been using black lights for years to detect these fluids on crime victims and at crime scenes. Paper manufacturers had begun adding phosphors to almost all white papers in the 1950’s. Thus, exposure to a black light will reveal forged documents that are purposed to predate the mid-twentieth century. Money counterfeiters face a similar problem- many governments mark large bills in distinguishable, yet hard to reproduce, patterns of phosphorous materials to thwart forgery.
How to improve the black lights lighting effect?
We know how the black lights work above, and understand that only a few of UVA lights would get through. When glow in completely dark room, the purplish light is soft and week. Then how to achieve more blacklight lighting effects? Is there any tip we can follow?
-Ensure a totally dark room or area.
-Work with white cloths and visible fluorescent materials.
-The more sensitive the material is, the brighter it glows.
-The more UV blacklight is applied, the brighter it glows.
-The closer the light source to the materials, the brighter they glow.
-Choose the best position and adjust light direction according to work site.
-For white cloths, if you want to hide your skin, please adjust the light direction and make sure only dim light hit your body.
-Visible fluorescent material recommended: face and body paints, glow sticks, balloons, bubbles, candles, tape, ink, T-shirts, gloves, posters, wall stickers, barware, tableware and etc.
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