These days it seems you can't switch on the TV without seeing someone waving an ultraviolet torch around. They are everywhere, from detective series, to natural history programmes and the reality shows where investigative reporters and health inspectors poke around inside dirty restaurants and grubby hotel rooms. So, the answer to your first question is yes, you do need an ultraviolet torch (or flashlight, if you're reading this on the other side of the big pond...)!
Q: So what is Ultraviolet Light?
A: Our eyes are sensitive to light in what's known as the visible spectrum; basically we see the colours red, orange, yellow, green, blue, indigo and violet (mixed together produces white light). Colours can be expressed as wavelengths, measured in billionths of a metre or nanometres (nm) and the visible spectrum goes from around 700nm (red) down to 390nm, which is the violet end of the spectrum. Ultraviolet or UV light has an even shorter wavelength, from 400 down to 100 nanometers. It's mostly invisible to us humans but we can just about make out the longer UV wavelengths, called the Near Ultraviolet (NUV) region.
Q: How come UV torches appear Blue?
A: That's the Near UV most UV lamps and torches emit. Many UV lights and torches also deliberately produce small amounts of visible light as well, as a safety feature, so you can see they are working. Most of the torches that we sell peak at between 385 to 395nm, which -- for our purposes - is the most interesting and useful part of the UV spectrum.
Q: Hang on, what do you mean, by 'Safety Feature'? Is UV harmful?
A: It can be, and just because you can't see it, doesn't mean it's not there. In fact that makes it even quite dangerous as you can be exposed to it without even knowing. The classic example is sunburn, which you may not realise is happening until it is too late. In extreme cases exposure to high intensity UV can even lead to skin cancer, due to the damaging effect of UV from the Sun on unoprtected skin.
Q: Should I be worried? Can a UV torch give me Cancer?
A: No, the torches that we sell are low output devices, a fraction of the power of a sun lamp for example, but UV light from the more powerful models is enough to irritate, and potentially harm your eyesight. We are talking about sustained and prolonged exposure, as may occur if you stared into any really bright light for a lengthy period. The point is you can't know how bright the torch is because you can't see the invisible UV light.
Q: How about the smaller torches?
A: A quick flash from one of our smaller torches isn't going to do any harm, but as a general rule you should never look directly into the beam from any UV torch.
Q: How can I protect my eyes?
A: If you are considering buying one of our more powerful torches you might also want to think about getting a pair of safety glasses with UV protective lenses. They are widely available from tool and DIY shops for a few pounds. UV Safety glasses are normally clearly marked and usually have amber coloured lenses.
Q: OK, duly noted: Now tell me what your torches are good for?
A: Some more quick science. The two most interesting applications for UV light, as far as we are concerned, are fluorescence and phosphorescence. Fluorescence is the property of many materials to emit visible light, when exposed to UV. In other words things that glows under UV light. Phosphorescence is similar, except that the glow continues when the UV light is switched off. Essentially this is stuff that glows in the dark. UV has lots of other uses, from killing germs to hardening plastics and whitening teeth but let's stick to torches.
Q: About time! Now what can I do with one?
A: Alright, let's begin with the yukky stuff and those infamous bodlily fluids, which turn up almost every week on NCIS, CSI, Bones, Cold Case and so on. UV fluorescence is a natural property of many organic substances.
Q: You have my attention - tell me more
A: We needn't go into too much detail, but if you want to see this sort of fluorescence in action take a UV torch into almost any toilet or bathroom (don't forget to turn the light out), and see what you can see... It should be quite a show, especially around the sink and toilet bowl, even if has been thoroughly cleaned. Residues of detergents and sanitisers may also show up as they often contain fluorescent chemicals. Human and animal urine glows very nicely under UV, which is why a UV torch is an essential piece of kit for health inspectors and pest controllers.
Q: Nasty, but what else glows in Nature?
A: You may have seen or heard that scorpions glow under UV light. They really do, and it's a truly weird phenomenon that no-one really understands. To be honest scoripions are not that common in the UK, though there are several well-established colonies, especially around ports and docks where they come ashore from ships, having hitched a ride in freight and cargo containers.
Q: I've seen UV lights in shops and banks - what's that all about?
A: UV torches have numerous security applications, once again exploiting the fact that many materials glow under ultraviolet light. Invisible (until exposed to UV) markings are applied to items of value to aid identification or to prevent copying and counterfeiting, you probably have a few examples in your pocket right now. Most banknotes, virtually all credit and debit cards, cheques, ID cards and so on normally have some UV marks or symbols. You may even see some coloured ink on the edges of banknotes. This is almost certainly a Smartwater dye residue, indicating that the note in question may have been stolen at some point. The containers used by security companies to transport cash and the money boxes in cash machines have anti-theft devices that spray the coloured dye, mixed with an invisible Smartwater, when the container is stolen. Smartwater glows under UV light and contains microscopic particles with unique identity codes. The chances are the villain will have traces of the dye on their clothes and skin after handling the stolen cash, which helps the police link the crook to the crime.
Q: Anything else?
A: How long have you got? The list is almost endless, but UV torches are popular with antique collectors and they're one of the best ways to test for crystals, ceramics and glass that contain fluorescent materials. One very good example is Vaseline Glass, also known as Uranium or Depression Glass, which contains tiny amounts of natural uranium and this glows bright green under UV light. It's also handy for quickly checking papers and documents. UV fluorescent chemicals have been added to paper, as a whitener, for the past 50 years or so, so if you see fluorescent specks in a 15th century manuscript, be a little suspicious...
Many minerals glow under UV. Our torches are great for 'charging' up luminous things that glow in the dark, much better than regular torches. If you doing a spot of decorating, turn out the light and shine a UV torch on the walls and you'll quickly see the bits you missed, or where the paint is a bit thin, due to the UV chemicals in many paints.
How about leak detection? Many fluids contain flourescent chemicals, and we're not just talking about industrial applicaitons, ordinary vehicle brake fluid, radiator coolant, some engine oils all glow under UV light, so if your car is making a mess on the ground you may be able to track down out where it is coming from with a UV torch. Check your newly washed clothes in the dark under UV light and see where the stains are, check how clean the sheets are the next time you stay in a hotel... The list goes on but the bottom line -- and we are nearly there now -- is that your life is simply not complete without at least one, and preferably two or more UV torches, and that's something we'll be only too pleased to help you with!
Q: Any more ideas...?
A: We are coming across new applications for UV torches all the time -- we recently discovered that they're a great way of finding lost golf balls (in the dark of course) as the plastic outer shell flouresces nicely under UV. If you have any suggestions, please let us know so we can add it to the list.
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