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| BLACK ( UV) LIGHT –
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| Extract from the Wildfire website
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| Clarifying Definitions
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| Black Light: Black light is similar to visible light, except it’s just beyond what the human eye can see. The wavelengths are shorter, and exists just beyond visible violet light, hence the name "ultraviolet." (See tutorial Science of UV.)
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| Fluorescence: A phenomenon whereby a substance absorbs light at a particular wavelength, then releases a longer wavelength light. This can happen anywhere in the light spectrum, but in the world of black light effects, this happens when a material absorbs long-wave ultraviolet light (a.k.a. black light), then releases visible light in return. (Fluorescence.)
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| Lamp: The "technical" term lighting designers use to refer to a light bulb. A lamp is housed in a fixture.
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| Luminescence: A general term for any kind of light produced by chemical or biochemical changes, electrical energy, subatomic motions, reactions in crystals, or stimulation of an atomic system. Examples of luminescence include fluorescence, phosphorescence, and bioluminescence (think fire flies, or those strange, glowing deep-sea creatures you see on nature shows).
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| Phosphor: A substance that exhibits the phenomenon of phosphorescence. Our Wildfire Glow Green Luminescent Paint has phosphors that cause it to glow in the dark.
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| Phosphorescence: Related to fluorescence, but "slower." Phosphorescent materials (phosphors) exhibit a sustained glowing after exposure to light or energized particles such as electrons. The mechanics are the same as in fluorescence, but it happens over time. Therefore, they continue to glow after exposure to light. Phosphorescent materials glow in the dark.
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| Photoluminescence: A specific kind of luminescence caused by excited electrons in an atom. Fluorescence and phosphorescence are examples of photoluminescence.
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| Ultraviolet Light: A broad term for a range of light just beyond visible violet light. Wavelengths are shorter and of higher energy than visible light. There are three main categories of ultraviolet light: short-wave, medium-wave, and long-wave (a.k.a. black light).
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| The Science Behind UV
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| What you need to know about black light in order to create spectacular, ultra-bright black light effects.
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| Black light is the common name for long-wave ultraviolet light (or UV light for short). Don’t worry. We’ll get to what exactly that means in a minute. For now, understand that UV light is just like visible light, except it has more energy. And you can’t see it.
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| Visible light and UV light are forms of energy known as electromagnetic energy. So are radio waves, microwaves, x-rays, and gamma rays. There is a whole spectrum of electromagnetic energy that encompasses a very wide range of energy levels.
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| Electromagnetic energy, like its name suggests, has both electrical and magnetic properties. But the really interesting thing about light is its dual nature: it sometimes behaves as a wave, and sometimes as a particle. It just depends on how you look at it, or how you study it.
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| In defining UV light, we’ll be thinking of those wave properties and will talk in terms of wavelength. In the tutorial on fluorescence, we’ll be looking at the particle nature of light.
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| Low energy light waves have very long wavelengths. Radio waves, for instance, can have wavelengths many miles long. Because they are low in energy, they are harmless to humans and pass through our bodies all the time without us being aware.
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| Conversely, very-high energy light waves have extremely short wavelengths, which can be much smaller than the diameter of an atom. Gamma rays and x-rays are examples of high-energy electromagnetic energy. They are deadly to all life, and even exposure to very low intensities is known to cause cancer.
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| Visible light is right in the middle of the spectrum—more energetic than radio waves, but not so energetic as to be harmful. (Microwaves have longer wavelengths, and lower energy levels than visible light. However, particular frequencies—those used in microwave ovens—are dangerous because they cause water molecules to vibrate and heat up.)
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| Wavelengths of electromagnetic energy between roughly 400 and 700nm (nm = nanometers, or one billionth of a meter) are visible to the human eye. The longer wavelengths—toward 700nm—are on the lower end of the visible spectrum, while the shorter wavelengths—toward 400nm—are on the upper end of the spectrum.
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| The visible spectrum is divided into the different colors we see. Red is on the low end, with longer wavelengths, while violet is on the high end, with shorter wavelengths. You may have taken a science class where you had to memorize the spectrum of visible colors: ROYGBIV. As you progress up the visible spectrum, you see a shift in color from Red to Orange to Yellow to Green to Blue to Indigo to Violet.
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| Beyond violet—just beyond what the human eye can see—is ultraviolet light. Although we can’t see ultraviolet light, certain birds, reptiles, and insects such as bees are able to see it. Imagine being able to see another “color!” It would open up a whole new world!
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| Ultraviolet Light Range
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| Ultraviolet light is really a broad name given to a range of wavelengths from around 100 to 400nm. UV light with wavelengths shorter than 200nm exists only in vacuum, since they are quickly absorbed by air or water molecules. This range is known as vacuum UV.
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| The other wavelengths, from 200 to 400nm, are broken up into three bands: long-wave UV, medium-wave UV, and short-wave UV.
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| The short-wave UV range, also known as UV-C, is from around 200 to 280nm. Short-wave UV is very dangerous and will cause severe burns. Staring straight into a light source emitting this range will cause blindness. Bacteria and other germs don’t stand a chance—which is why this range is so useful for germicidal applications. Short-wave UV at 254nm is often used to purify air, water, and food because it kills 99.9% of all pathogens. Fortunately for all of us on earth, short-wave UV from the sun is completely absorbed by the upper atmosphere.
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| The medium-wave UV range is less energetic than short-wave, but still harmful to humans. Medium-wave UV, or UV-B, is defined as having wavelengths between 280 and 315nm. This is the range that is responsible for sunburn...but also skin tanning. The lights used in tanning salons produce medium-wave UV light. However, prolonged exposure to medium-wave UV is believed to cause skin cancer, though there has been some recent controversy over whether this is entirely true.
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| Long-wave UV, or UV-A, is the kind used in entertainment applications. This is what’s known as “black” light. (“Black” because you can’t see it.) In comparison to short-wave or medium-wave UV, long-wave UV is pretty safe. This range is defined by the wavelengths between 315 and 400nm. Remember that 400nm is about the extreme edge of visible light. So this range is just beyond what humans can see.
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| So how is it we can see under black light? Well, there are two reasons.
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| 1. Even artificial UV light sources don’t emit pure UV light. Visible light is also present. Depending on the technology used and the manufacturer, there can be quite a bit of, or very little visible light emitted by the UV light fixture.
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| Even in the presence of pure UV light, you could potentially see a great deal. It would all depend on the degree of UV sensitivity of the materials around you. UV sensitive materials actually give off visible light themselves. And that brings us to the topic of fluorescence.
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| How Fluorescence Works: Why Certain Objects Glow Under Black Light
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| A brief explanation of how fluorescence works, and how it applies to creating black light effects.
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| The photo on this page shows a collection of various fluorescent minerals under long-wave, medium-wave and short-wave UV. Many substances will react in the presence of UV light, giving off visible light in return. The materials “glow” because they are literally giving off visible light.
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| A collection of fluorescent minerals under long-wave, medium-wave, and short-wave UV light.
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| (Photo by Hannes Grobe.)
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| A complete explanation of this phenomenon is beyond the scope of this tutorial. (It would take several chapters of a chemistry or physics textbook to explain it completely.) But we’ll give a brief explanation here...
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| Remember the dual nature of light we mentioned in the last tutorial? When light comes into contact with an atom, it behaves more like a particle rather than a wave.
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| A “particle” of light is called a photon. It has no mass—just energy. You can think of it as a packet of energy. When this packet of energy (photon) comes into contact with an electron in the outer regions of an atom, the electron absorbs the energy and jumps to a higher energy state. It moves to a higher orbital, as physicists call it.
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| The electron doesn’t stay there, though. It releases that energy as a photon of light. BUT…this new photon has a slightly lower energy level (and thus a lower wavelength).
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| Every substance interacts with light in this way. But typically we don’t see it, because the light given off is either of a wavelength we can’t see, or there is so much ambient light present that we don’t see the visible light being emitted.
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| If it’s a photon in the UV range striking an atom, and if the atom emits a visible photon in return, the material is UV sensitive. This is the glow effect associated with black light, and you typically can’t see it unless there is complete darkness and you have an artificial light source emitting UV light. The more sensitive the material is, the brighter it glows. And the more UV light is applied, the brighter it glows still.
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| BUT, there’s more to the story. You see, different so-called UV sensitive materials will react best to certain wavelengths. In the photo, you see minerals in the presence of long-wave, medium-wave, and short-wave UV light. In other words, the entire range of UV light was applied to get those materials to glow.
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| In entertainment applications, we’re typically limited to long-wave UV, which is safe forour audiences, customers, or friends. So in choosing UV sensitive materials, we’ll want materials which react best under long-wave UV light. And that’s exactly what black light sensitive products are designed to do (although some are better than others.)
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| When selecting a fixture, it’s been our experience that you’ll get the best results—the brightest effect—with a fixture peaking at around 365nm. Right smack in the middle of the long-wave UV range.
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| When you think about it, it makes sense: This wavelength represents a compromise. Any fixture will emit a range of frequencies. Not just one. So if a fixture peaks in the middle of the long-wave UV range, you’re covering the entire spectrum of black light...and getting the most out of your UV-sensitive materials.
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| The Wildfire Effect Explained: Defining The Signature Black Light Effects
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| Black light effects take advantage of the property of fluorescence by shining long-wave ultraviolet light (a.k.a. black light—see science of UV) on certain materials that fluoresce under it.
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| Fluorescent materials include special luminescent paint, water-dye, screen ink, makeup, and many natural or man-made materials. (Our 2007 Special Edition Catalog: The Ultimate How-To Guide To Creating Spectacular, Ultra-Bright Black Light Effects lists many of these commonly available UV-sensitive materials.)
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| The classic black light effects include fluorescent visible images, invisible images, dual images, day/night transitions, and 3-D images.
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| Visible Fluorescent Effects
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| Visible fluorescent images (whether created by paint, makeup, water-dye, or other materials) appear a bright colour under normal light, and fluoresce brilliantly under black light.
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| Fluorescent images can be enhanced under black light by surrounding the fluorescent material with black, or completely non-fluorescent material. Any non-fluorescent material will appear black under true black light, and will help create a more defined image.
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| This is put to dramatic use with fluorescent body paint lit only by long throw black light fixtures. What little visible light is produced doesn’t quite reach the stage. The body will appear black—almost completely unseen—while the body paint fluoresces under the black light.
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| Invisible Fluorescent Effects
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| Invisible images appear white (or clear) or otherwise non-descript under normal light, and appear only when black light is applied. This property is often used to verify currency, identification, or other official documents. It’s also used to dramatic effect in the entertainment industry.
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| Invisible fluorescent materials typically need shorter-wavelength black light in order to brilliantly fluoresce. While many visible fluorescent materials will glow even at 400nm (a high energy visible violet), invisible materials will respond better at a shorter 365nm wavelength, which is produced only by quality metal-halide or fluorescent black light lamps.
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| Dual Image Effects
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| Dual images are a special type of invisible image. One image will appear under normal light, while a different image appears only under black light. The black light artist will work on both images simultaneously, alternating between working in normal light and black light.
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| Day/Night Transition Effects
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| Day/night transition effects are common in a lot of black light images. It’s a type of dual image effect where a day scene appears under normal light, turning into a night scene under black light.
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| 3-D Effects
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| The property of fluorescence can create dramatic 3-D effects, as anyone riding “The Mummy’s Revenge” ride at Universal Studios can attest. (One of our credits, by the way.) 3-D glasses enhance the effect and make lighter colors appear closer, while darker colors appear to be further away.
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| (If this article look a lot like the Wikipedia definition for black light effects, it’s because we’re a major contributor to that entry)
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| Technologies That Produce UV Light—Which Ones Are Most Effective
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| A brief survey of black light technologies, how they work, and which ones produce the best results for the brightest possible black light effect.
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| UV light can be produced by a variety of different sources. This tutorial introduces the different lighting technologies that produce black light, and explains which ones produce the best results for ultra-bright black light effects. But first, we need to set something straight about wattage.
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| Why Wattage is Misleading
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| Before we launch into a survey of the different types of lamps producing UV light, it’s important to understand some of the terminology used. Lamps are rated for a particular wattage. And wattage refers to power consumption—how much power is used.
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| The actual output, or brightness of the lamp, is directly proportional to its wattage. In other words, the higher the wattage (the amount of power consumed), the greater the output.
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| However, a particular wattage does not imply a definite level of output. Efficiency is what determines how much of that power consumption is converted to actual output.
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| Think of a 40W fluorescent lamp and a 40W incandescent lamp. The fluorescent lamp is always brighter because it is more efficient at converting power into actual output. Incandescent lamps are not as efficient (much of the power is converted into heat), so the output is less.
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| We’ve also got to look at the type of output generated. Think of a red lamp versus a blue lamp. Red light is a different type of light than blue light. It has a longer wavelength.
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| Different lamps will produce light of different wavelengths—actually multiple wavelengths—and in different proportions compared to other lamps. This is referred to as the quality of output. The type of light produced.
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| A good black light, then, must have an output that is almost entirely in the long-wave UV range, and not in some other range, such as visible blue or violet. We’ll be discussing different black light technologies and the quality of output they produce.
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| Tungsten-Halogen Incandescent Lamps
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| You’ll find novelty shops selling so-called incandescent black lights. Tungsten-halogen incandescent bulbs do produce a small amount of UV light, but it’s so small in comparison to the visible light it produces, that most of the wattage is wasted on visible light. Using purple glass just creates purple light...not true black light. And that’s really what an incandescent black light is: a purple light. Or to be technical, visible violet. Even if Wood’s glass were used (a special glass that filters all but UV light), the UV output is so tiny compared to the wattage, you’d waste a lot of power producing heat.
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| Try this experiment, and you will see the difference: using lamps of the same wattage, compare the brightness of a UV sensitive piece of material under a fluorescent lamp versus an incandescent. There is just no comparison. While incandescents may be fine for casual hobbyists, they are worthless if you want to create a dramatic, ultra-bright UV effect.
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| Light Emitting Diodes (LEDs)
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| LED technology is advancing rapidly, and can be made to produce light of any wavelength. They’re energy efficient, don’t produce massive amounts of heat, and they’re long-lasting. Forensic investigators will often use UV LED flashlights in crime scene investigations. So what’s not to like about them?
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| There are two principle reasons: wavelength and output.
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| At this time, UV LEDs are typically available with peak wavelengths of 400nm, 390nm, or 385nm. You can get shorter wavelengths, but the LEDs begin to get prohibitively expensive. As we mentioned in the tutorial on fluorescence, 365nm is the “sweet spot” for creating ultra-bright black light effects. It’s right in the middle of the long-wave UV range, and a fixture peaking at this wavelength covers the entire black light spectrum.
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| UV LEDs peaking at 365nm are available, but at this time, they are just too costly. Fluorescents still offer a more cost-effective solution. Furthermore, because of the shape of the spectral transmission curve of a UV LED, one peaking at 365nm would be a bit dangerous to look at because it would emit some medium-wave UV (UV-B), as well. An LED fixture with 365nm LEDs would need a special filter glass to filter out visible and dangerous medium-wave UV light.
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| What about output? The output of a typical LED is small compared to other lighting technologies. LED fixtures are made with an array of LEDs, which add to the cost. This will likely change in the future, however, as the technology advances. At this time, there are no UV LED fixtures on the market with comparable output to even our introductory black light fluorescent fixtures.
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| In short, LEDs offer a lot of promise. And this may very well be the future of black lighting technology. But we’re a long way from the day when an LED fixture is comparable to other technology both in output and affordability.
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| Mercury-Xenon Arc Lamps
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| Xenon arc lamps can be made to produce massive amounts of light—up to 15 kilowatts. These lamps are vacuum-sealed quartz enclosures filled with xenon gas. Electric current “arcs” across a gap between two terminals and creates a small ball of plasma.
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| Pure xenon arc lamps produce light across the entire spectrum—including UV light—and closely mimic sunlight. However for UV applications, adding mercury vapor to the mix will produce massive amounts of UV light across the entire UV range. Because of this, they are often used for curing, sterilization, and ozone creation.
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| For entertainment applications, you’d obviously need to filter out the medium-wave and short-wave UV light. But mercury-xenon technology is extremely expensive compared to fluorescent or metal-halide.
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| These lamps will outshine even the brightest metal-halide lamps. However, we’ve yet to see an entertainment application requiring this much output. It’s overkill and it’s expensive.
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| Deuterium Arc Lamps
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| This technology is similar to xenon arc lamps in that gas is under pressure inside a vacuum-sealed enclosure with a gap between two electric terminals. An electric current arcs across the gap and excites the deuterium, producing a continuous spectrum of UV light. (Deuterium is a stable isotope of hydrogen, containing an extra neutron in its nucleus.)
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| This technology might be ideal for entertainment applications except for its higher cost. It is currently used in scientific applications such as spectroscopy, where a continuous spectrum of UV light is desired.
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| Fluorescent Lamps
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| All fluorescent lamps operate under the same principle. Mercury vapor mixed with a rare earth gas such as argon or xenon is excited by an electrical current. The excited mercury produces short wave UV light, which then causes a powdered coating on the inside of the glass to fluoresce, giving off visible light (or black light) in return. The powdered material can be made from a variety of substances that emit different kinds of light—colored, white, full-spectrum, black light, etc.
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| In the case of black light, or “blacklite blue,” as it’s called in the lighting industry, the fluorescent coating will give off long wave UV light after absorbing the short wave UV light. Black light blue lamps use a special glass called Wood’s glass, which filters out most visible light produced by the fluorescing powdery substance.
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| A good black light fluorescent bulb will have a peak wavelength of about 365nm—right in the middle of the long-wave UV range, and perfect for producing really good black light effects as long as a good electronic ballast is used.
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| Black light fluorescent lamps are inexpensive, easy to acquire, and are an excellent source of UV light. A good quality lamp in a properly ballasted fixture is the ideal source for many black light applications when the fixture can be mounted close the effect and a wash of black light is desired. For more information on fluorescent technology, see the product description page for our new SableLux™ Fluorescent Black Light Blue Lamps.
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| Metal Halide Arc Lamps
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| Metal halide lamps contain a high-pressure mixture of argon, mercury, and various metal halides. (A halide is an ionized form of a halogen, which is the general name for a group of elements: fluorine, chlorine, bromine, iodine, and astatine.)
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| An electric current excites and ionizes the argon gas, which helps the electric current arc across a gap between two terminals. The heat generated by the arc then vaporizes the mercury and metal halides, which produce light as the temperature and pressure increases. The mixture of halides will affect the nature of the light produced and its intensity.
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| In our patented IronArc™ Metal-Halide Lamps, we’ve used iron iodide to boost the UV output by an average of 35% over conventional metal halides. This is one of the key secrets behind the legendary Wildfire Effect. And it’s how you can get the brightest possible black light effect for your application. Plus, compared to other lighting technologies, metal-halide lamps are quite inexpensive.
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| To sum up, fluorescent and metal-halide technology remains the best solution for black light applications. And Wildfire constantly works to get the most UV output out of these technologies with our patented IronArc™ UV Metal Halide Lamps and SableLux™ Black Light Blue Fluorescents.
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| The FLAME™ Formula for Creating Powerful Black Light Effects
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| When it comes to creating the brightest possible UV effects, there are four absolutely critical elements you must take into account. We’ve condensed these four factors into an easy-to-remember acronym we call the “FLAME” formula.
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| F is for “Fixture”
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| Other than optics, there are two factors to consider when selecting the right fixture for your effect: output and wavelength. Just because two fixtures are each 400 Watts doesn’t mean each fixture has the same amount of output…or output at the appropriate wavelength for maximum brightness.
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| For best results, the fixture should peak at 365-368 nm. Many so-called black lights aren’t really black lights at all. (See the next article, “A Brief Survey of Black Light Technologies” for a more detailed discussion on this.) For example, there is the much-touted UV LED in recent years. Most UV LED’s produce light at 385nm to 400nm. White shirts and visible fluorescent materials will start to glow at around 400nm, but that’s really high-energy visible violet— not a true black light.
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| UV LED’s with wavelengths of 385nm or 390nm produce better results, but still fall short of the 365nm “sweet spot.” The biggest problem with longer wavelength LED fixtures is that invisible fluorescent materials don’t respond well, if at all. To get the best results for all UV sensitive materials, use a fixture peaking at 365nm.
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| All of Wildfire’s Long Throw and fluorescent Effects Master fixtures peak between 365-368nm. This combined with many other factors make them the best black lights for creating the brightest possible effect. We don’t expect you to take our word for it without an explanation, so we challenge you to discover what sets our fixtures apart by taking a look at page 12 and 30.
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| In short, choosing the right fixture is crucial.
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| L is for “Length” (of the distance between the fixture and the UV sensitive materials)
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| This is a fairly obvious point. The closer the light source to the materials, the brighter they glow. So you’ll want to mount your fixture as close as possible to the effect. In some cases, such as stage applications, it’s impossible to have the light fixture right next to the materials. In those cases, you’ll need a good long throw fixture, such as our 400W Flood (p. 18). Our Long Throws have an effective distance up to 70 feet, or more, depending on the other factors listed here. For closer applications needing broad coverage, our VHO (very high output) fluorescent Effects Masters cover up to 50 feet or more.
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| A is for “Ambient Lighting”
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| If you have a lot of visible light present, much of your effect will be washed out. You’ll want to get rid of as much ambient light as possible. Cover windows, shut off music stand lights, turn off any unnecessary light sources. Do everything you can to cut down on ambient lighting.
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| If you’ve done everything possible, but you still have ambient lighting issues, don’t worry. You can make up for it with the right combination and placement of fixtures. You’ll just be spending more money to counteract ambient lighting.
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| Wildfire fixtures are powerful enough to show an effect even with a lot of ambient light present. Every year at LDI—the trade show for the lighting industry—we prove the effectiveness of our fixture with ambient light present. Imagine the challenge of creating a UV effect with every exhibitor showing off their latest light fixtures!
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| M is for “UV Sensitive Materials”
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| It doesn’t matter how much UV light you’re throwing on the effect if the materials aren’t UV sensitive. In fact, non-UV sensitive materials will appear black under a good black light with zero ambient light
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| present. You want materials with the greatest possible sensitivity to long-wave UV. The more sensitive the material, the brighter it glows.
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| Because of this, we’ve formulated all of our paints to be super-saturated with UV-sensitive pigments. In other words, there’s no possible way to pack more pigment into these paints, and that makes them the brightest you can possibly get!
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| In short, make sure you’re using materials that are really responsive to black light. Stick with reputable manufacturers, or do some experimenting on your own. There are many naturally occurring or commonly available UV sensitive materials available. Check out the vignette “Everyday Fluorescent Materials.”
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| E is for “Effect”
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| This is the last part of the equation—the result that happens when the four critical factors are working together. If you’ve done everything right, you should expect a very powerful UV effect. So always remember to use the FLAME formula every time you set out to create a “Wildfire Effect!”
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| How To Get Maximum UV Output Out Of A Fluorescent Black Light Bulb
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| An explanation of how black light fluorescent bulbs work, and how to boost their UV output.
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| Inside the tube of a fluorescent bulb is a mixture of mercury vapor and a noble gas, such as argon or xenon. The mercury provides conductivity from one electrode at one end of the tube to the electrode at the other end. An electrical current will excite this gas mixture, which then emits shortwave ultraviolet radiation, or UV-C light. (Tutorial Science of UV.)
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| The Fluorescent Powder Coating
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| A fluorescent powder coats the inside of the glass tube and reacts to the UV-C light, emitting visible light in return (Tutorial Fluorescence) — or in the case of a fluorescent black light, long-wave UV light (black light), which is filtered through a special purple glass called Wood’s glass.
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| The more powerful this fluorescent material…in other words, the more strongly it reacts to the UV light, the brighter the output of the bulb. So all other things being equal, you can increase the output of the bulb by using a more reactive fluorescent powder coating. Read about how we’ve done this with our SableLux™ Fluorescent Black Light Blue Lamps.
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| The Tube Diameter
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| You can also increase the UV output of a fluorescent bulb (lamp) by reducing its diameter. With a smaller diameter tube, the fluorescent material is closer to the center of the tube and will fluoresce brighter. Most black light lamps have a diameter of T10 or T12. (The number refers to eights of an inch. So a T10 is one and one-eighths of an inch in diameter.)
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| Wildfire has just released a brand new fluorescent lamp with a diameter of T8. (Or one inch.) This may very well be the most powerful fluorescent black light available on the market.
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| VHO Electronic Ballasts
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| As powerful as this new lamp is, however, the fixture the lamp is housed in has as much to do with output as the lamp itself. For instance, the right fixture can double the standard output of a fluorescent lamp with a very-high output (VHO) electronic ballast. To find out more on how this works, take a look at our Effects Master fixtures.
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| In short, to get the most UV output from a fluorescent black light bulb, you want three things...
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| 1. A powerful fluorescent coating inside the tube.
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| 2. A smaller diameter tube.
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| 3. A VHO (very-high output) fixture, which doubles the wattage of the lamp.
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| http://www.wildfirefx.com/resources/tutorials/index.aspx
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