FAQ - Buying a Portable UV Mineral Lamp
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(I wrote this FAQ many years ago. A lot has changed since, but the content is still valuable - M Cole).
In the last couple of years there have been several new manufacturers and suppliers of portable UV lamps – great news for the Glowhound's hobby. But, I have not seen an independent comparison of lamps (until now), and the advice I see coming from some manufacturers is (in my opinion) misleading and borders on dishonesty. I don't have the time or resources to devote to actually testing each lamp out there and providing a side-by-side comparison, but I do have the ability to point out what you should look for when buying a field lamp. That is the purpose of this FAQ – What to look for in buying a field lamp. Please keep in mind that I only have used two lights: the SuperBright made by UV Systems and the Way Too Cool line of lamps. I have no field experience with any other lamp. I do build my own lamps for use in the field and at home, but I do not sell lamps – thus I do not have a hidden agenda. I believe that competition is good for our hobby and hope that eventually someone will figure out how to build a good cheap lamp so that everyone can afford to enjoy these wonderful glowrocks as we do.
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Q: What are the most important factors in considering a specific model lamp for field use?
A: A lot depends on the individual. Cost, weight, brightness, reliability and power consumption are the main concerns I would have when buying a portable lamp for field use.
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Q: What do these lamps cost?
A: They range from cheap to expensive. It's up to you to shop around but there are some basic facts that you should be aware of. Most lamps use a Hoya 325c filter which is probably the most expensive component in the lamp. They all use a UV bulb, and they all have an ballast/inverter. These three items should cost each manufacturer pretty much the same – so if they have a bigger filter, or two lamps, or more watts (higher power) the costs will increase accordingly. When comparing costs make sure you compare the filter area and lamp UV wattage.
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Q: I've seen a person selling an unfiltered shortwave light for mineral use on Ebay – cheap – and he claims it "outshines" all other "filtered" units.
A: HOGWASH!!!! That lamp is useless. UV tubes put out a tremendous amount of visible light. This light overwhelms the UV and washes out the fluorescent response of almost all minerals. You may be able to see the response of a very bright Willemite/calcite from Franklin but I can't think of too many more minerals that you will be able to find with an unfiltered light. This is either a scam or a terribly misinformed seller – do not buy an unfiltered light.
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Q: How are these lamps powered?
A: Portable field lamps require portable power. That means a battery; the most common being a 12VDC lead acid battery (the same type of battery used in your car, only a little smaller). Batteries are rated in Amp Hours (AH). The battery typically sold for use with the Superbright is a 7AH battery. This means if the Superbright uses 1 amp per hour, the battery "should" keep it lit for 7 hours (it doesn't really work that way because a lead acid battery dies slowly as it is being used, and when the voltage drops below 10 volts, the lamp shuts down). You may get 4 or 5 hours use out of the battery. (BTW – take a look at the NiMH battery packs being offered on Ebay – they are half the weight and twice the power of a lead acid battery - or better yet, look into LiFE technology). More here...
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Q: Some manufacturers sell an "Inverter" and a battery to use their lamp in the field – what does that mean?
A: (Disclaimer - I prefer a battery operated lamp, but my DIY section on MinerShop.com shows a lamp using an inverter. If you want to save some $$$ and are willing to deal with the expense/hassle of an inverter, it's a good way to go. But battery lamps are better, but also beyond the technical capability of most DIY'ers.) That said, an inverter uses a battery to generate 110vac (house current). The lamp manufacturers who recommend this solution mean they have not taken the time (or trouble) to design a lamp for operation on 12VDC. They're using a "cop out" by asking you to buy not only the heavy clunker 12VDC lead acid battery, but now an extra piece of equipment to turn that battery voltage into 110vac so their lamp will work in the field. Why is this bad? Several reasons; first, it's an extra piece of gear to carry around, secondly another thing to break while in the field, and third – it is a terribly inefficient use of battery power. An inverter consumes power just like anything else. It takes battery power to turn that good ol' 12vdc into that nasty 110vac. Every inverter does this differently, and how good they are at it is called "efficiency". As you might expect – efficiency is the term inverter companies use to compete with each other. The higher the efficiency the better the inverter. But – it's all hogwash. It'll be real hard to figure out the true efficiency of an inverter for a given load without actually testing it. Some claim as high as 90% efficiency but I would use 70% as a good rule of thumb. This means that 30% of the battery power (amps) is used just by the inverter to "make" 110vac. So, if you have a 10AH battery (puts out 1 amp for 10 hours), it will really only put out 7 amps because the other 3 amps are used to run the inverter. Short story – inverters eat up valuable battery power. Only buy a lamp that has a DC input.
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Q: What should I look for in weight?
A: That's up to you! I do most of my prospecting in the mountains of Greenland. Every ounce matters! I have no choice with my lamp – it works and it weighs. But I do have a choice in batteries. I have long ago thrown out my clunky lead acid battery and replaced it with much smaller, more powerful and much lighter NiMH battery packs, subsequently replaced by LiFE technology. But the battery is the most important factor determining weight.
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Q: Every manufacturer has a different claim about brightness – what's the real story?
A: This is a hard one to answer without actually testing each lamp to prove/disprove the manufacturer's claims. Seems like a hobby organization ought to tackle this one – it would be a great service to their membership.
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But – there are some common sense rules you can apply. Wattage of the lamps indicates brightness. The more watts, the brighter the lamp. Some manufacturers "overdrive" their lamps (stuff more power into them then the lamps are rated for). It's sort of like pulling a boat with a car instead of a truck – you can do it, but the car will fall apart a whole lot quicker than normal. Same with the lamp. For the record – that's ok in my book. I'd rather have a bright light where I have to replace the bulb more often, but it helps me find more glowrocks. (Some may use two lamps instead of just one – same story – just add up the watts and compare). But, it's even a little more complicated than that; it's not a simple matter of brightness (watts). You also have to factor in the type of reflector used and the design. A 13 watt lamp with a properly designed reflector would most likely outperform a 25 watt lamp with no reflector (or one that has a UV coating preventing it from reflecting UV). Worse - watts refers to the power consumption and really has nothing to do with the UV output of the lamp (that's buried deep down in the specs of each individual lamp - something UV light manufacturers don't even talk about).
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Q: Anything else to consider when it comes to brightness?
Filter area – the larger the filter area, the more UV light is gonna get out! Buy the lamp with the largest filter area. Sadly, because the filter is the most expensive component in the lamp, that lamp will most likely be the most expensive to buy. If it's not, wonder why....
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Q: I use my light at night on rocky terrain and fall down a lot. What should I look for in a good field lamp?
Reliability and ruggedness: Large filter area, but figure out some way to protect the very expensive filter glass so when you trip and fall, the glass has a chance of surviving.
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Q: Should I get three different units – one for SW, one for MW and one for LW?
A: Sure, if you've got an unlimited budget and an SUV that's gonna carry you directly to your collecting spot. Real world: why does anyone need anything other than shortwave? I can't think of many minerals that only lights up under MW or LW (perhaps ruby - but you don't need a lamp for those). If it lights up under SW I will most likely carry it home. Then I'll check it out under LW and MW; maybe get a nice surprise. Why carry other lamps? Why spend extra money for combo lamps? If you really think you need LW, check out one of the LW LED flashlights. They work for most LW minerals if that's all you're looking for – and are dirt cheap! (But the cheap ones are really crappy).
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