UV LAMPS

As well as making rocks fluoresce, UV lamps are used for lots of other things, such as killing germs, examining passports, locating cracks and faults in metals and more.  So they come in many configurations.  If you get a lamp that is intended for some other use, it probably won’t work for seeing minerals fluoresce.

For fluorescent mineral use a lamp needs to have a filter.  All UV light sources emit visible light (bright blue) as well as UV.  Unless blocked, the visible light will make it difficult or even impossible to see any fluorescence.  This applies to all types of UV lights.  So what we call “UV Filter Glass” allows as much UV as possible to pass through, but blocks (almost all) visible light.  UV Filter Glass always looks black and opaque like the glass in welding goggles.  This is the complete opposite of camera UV Filters which are clear and designed to block UV, whilst allowing visible light to get through.  (Note that most (not all) digital cameras do not need a UV filter because UV does not affect their image sensor. It was the film in older cameras that needed protection from UV.)

The Filter Glass is the most expensive component in a UV lamp.  It is what pushes the price up.  Consequently manufacturers often reduce the area of filter glass in their lamps.  Although this reduces the price, it decreases the effectiveness by reducing the amount of UV getting through, and hence reduces the brightness of fluorescence. When making display cabinets with built-in UV lamps, we do not skimp on Filter Glass.  Yes, that makes them a bit more expensive, but it greatly improves the brightness of fluorescence which, after all, is what we are striving for.

Note: Long Wave filter glass is sometimes called “Wood’s Glass“.

UV LED TORCHES

If you google “UV TORCH”, you will find thousands of places where you can buy hundreds of  UV LED torches.  Most of them are completely useless for seeing fluorescent minerals because they have no filter.  When you look at a photo of a UV torch with the power off, if you can see anything at all through the front lens then that torch doesn’t have a filter and will be no good for mineral fluorescence.  The front lens needs to look like a black circle.  If a filtered torch is turned on in the photo, you will only see a black circle with a very faint reddish purple glow towards the centre.  If you see individual LEDs or bright mauvish-blue, there is no filter.

A new LW UV torch has hit the market.  It has revolutionised what we can see under LW, and it is cheap!  It makes ALL* other LW torches obsolete.  It is VERY bright and I have discovered LW fluorescence in pieces that I thought we non-fluorescent.  It’s called the Convoy S2+ 365 nm UV torch and you can see it here.  Unfortunately it comes without a filter, but you can get one from places such as this.  * There are better very powerful UV torches now available, but they are very expensive – 20 or more times the cost of the Convoy.  You will find a lot more about this flashlight on Natures Rainbows here.  NOTE:  Prices asked for the Convoy differ wildly – don’t pay more than Gearbest charges!

At the moment, UV LEDs are all long wave, except for very expensive experimental MW and SW ones.  So an LED torch, even with a proper filter, will only get a response from the 10-15% of fluorescent minerals that glow under LW.  But you can find fluorescing scorpions!  (I have a feeling that new and powerful LW LEDs such as described in the preceding paragraph may increase this figure.)

A note on “UV Lasers”.  Laser pointers labeled as UV or 405nm emit a strong beam of light just above the UV range into the violet.  This light can produce strong fluorescence, and you can have a lot of fun making rocks fluoresce using a 405nm laser.  However, they emit a lot of visible violet light which will stop you seeing the fluorescence properly.  You need to wear UV blocking spectacles, preferably blocking everything up to about 420nm.  Of course, you must take care never to let anyone look into a laser pointer.  Only lasers with power less than 1 milliwatt are legal in Australia.

PORTABLE UV LAMPS

If you want to go out at night and search for fluorescent rocks you need a portable, battery operated UV lamp (usually 12V).  Unless you want to crawl around with your lamp just a few centimetres above the ground, you need at least 9 watts of power.  13W or 18W are better, but heavier.  I use 9W lamps in the field.  Built-in batteries are too small to give you enough time before re-charging is needed, so 9W or higher lamps require a separate battery to be carried, usually in a battery pack with a shoulder strap.  Lithium ion and NiMH batteries are good;  sealed lead acid (SLA) batteries are heavier but cheaper and probably less finicky.  You can find a lot of helpful ideas about lamps and batteries here.

DISPLAY UV LAMPS

If your specimens are on shelves, or laid out on a table you can use a portable lamp to show them rock by rock.  However if you want to create the magic of having them all glowing together you need a display lamp. You can have them spread out on a table or bench with the display lamp suspended above them, or you can have them enclosed in a display cabinet.   The more powerful your lamp, the more specimens you can light up, and the brighter they will glow.  How bright fluorescence is relates directly to how powerful the UV lamp is, and of course how far from the lamp the specimen is.  So the rule is simple:  Get the most powerful lamp you can afford!

WARNING.  Display lamps put out a lot of UV.  You must have a set-up that prevents people looking directly at the UV light source. Click here for ways you can achieve this.

BUILT-IN UV LAMPS

Building UV lamps into a display cabinet allows much greater flexibility.  You can choose whatever mix of wavelengths you want, and you can have as much UV power as you need.  The display below was made for a museum situation where there was limited darkness available, so a lot of UV was needed to enable the fluorescence to compete with ambient light.  In fact, there are eight 95W SW tubes and three 36W LW (BLB) tubes installed.  The area of filter glass is 0.2 sq m, or 310 sq in.  These are all big numbers and quite costly, but the effect is nothing short of amazing.