Bob's Rock Shop Product Review
UVTools M100 Ultraviolet Light Kit

Reviewer's Note: UVTools is currently offering the M100 with an enhanced kit that includes a longwave ultraviolet tube in addition to the normally supplied shortwave tube and six fluorescent specimens at the promotional price of $59.99. This is a no-brainer deal offering exceptional value for anyone considering the purchase of an entry level ultraviolet light or needing a portable unit for field work. See UVTools 6 Watt Field Lamp Special Promotion.

UVTools M100 6W Ultraviolet Light Kit Special M100 Enhanced Kit with Ultraviolet Lamp, Shortwave and Longwave Tubes, 6 Fluorescent Specimens, and Safety Glasses. Also included on CD is "The Story of Fluorescence" e-Book and and a Fluorescent Mineral Slide Show.

I recently acquired a UV Tools M100, an ultraviolet light regularly priced under $100 that has caught my eye in terms of features and performance for its price. The M100 is a battery powered field light employing a 9 inch, 6 watt shortwave ultraviolet tube in conjunction with a quartz filter as its ultraviolet light source. The M100 comes packaged as a standard kit that includes a pair of polycarbonate safety glasses and a fluorescent mineral specimen.

This light will serve nicely as an entry level ultraviolet source for rockhounds with a developing interest in fluorescent minerals and will also make an excellent educational gift. The science underlying the phenomena of fluorescence in minerals runs deep. There is also a good deal of "wow lookit that" factor here, and so I am keen on ultraviolet lights and fluorescent minerals as vehicles for stimulating and involving inquiring minds in the science part of Earth science.

UVTools M100 FlashlightThe overall dimensions of the M100 are approximately 10 1/2" long x 2 5/8" high x 1 3/4" wide. Loaded with batteries the M100 weighs 1 pound, 6 1/2 ounces. The M100 is compact and light enough to stow and field carry in a small day pack or a belt pack with a large carry pouch when not in use. An adjustable carry strap is incorporated for field use.

Because ambient visible light washes out and obscures the relatively weak light emitted by fluorescing minerals, the effect is best viewed in the dark. This also means collecting in the dark. Integrated into one end of the M100 is a visible light flashlight, a rather nice touch on an ultraviolet field light. The flashlight employs a single, high output LED, and while it is sufficiently bright to help aid you from stumbling over rocks or off a cliff in the dark, I was less than impressed with the brightness of the light output by the M100's flashlight compared to dedicated purpose, multi-LED flashlights I've used.

UVTools M100 SwitchA clearly marked 3-position sliding switch is provided on the M100 to control the flashlight and ultraviolet lamp. The switch is moved to one end position to turn on the ultraviolet lamp and to the other end position to turn on the flashlight. All off in the center position.

Three D-cells are required to power the M100, and batteries are not included. Batteries are installed by unscrewing and removing a threaded cap on the end of the M100 opposite the flashlight. Standard 1.5 volt alkaline or rechargeable 1.2 volt NiMH or NiCD batteries can be used. I elected to power my M100 using 1.2 volt, 2500 mAh rechargeable NiMH batteries, as they are more economic over time than one-shot alkaline batteries. I had some initial concerns that the lamp output might suffer with 1.2 volt rechargeable verses 1.5 volt alkaline batteries. It would require an ultraviolet light meter, which I didn't happen to have at hand, to perform an empirical test and actually quantify any difference in ultraviolet output using the different type batteries.

What I was able to test and conclude is that to my eye at least, using 1.5 volt alkaline batteries over 1.2 volt NiMH batteries did not provide a discernable difference in the fluorescence of specimens viewed with the light, and that 1.2 volt NiMH batteries work for me in this application. Because alkaline batteries have a higher storage capacity than consumer grade rechargeable NiMH batteries, they may be preferred for remote or extended field applications entailing longer periods of use where line power to operate a NiMH battery charger is unavailable.

F6T5GL Shortwave Ultraviolet Tube With The M100's Cowl And Filter Removed F6T5GL Shortwave Ultraviolet Tube With The M100's Cowl And Filter Removed

The shortwave ultraviolet lamp installed in the M100 is a 6 Watt F6T5GL germicidal ultraviolet tube, 9 inches in overall length with a G5 bipin base. The construction and operation of germicidal ultraviolet lamps are similar to ordinary low pressure mercury vapor fluorescent lamps, but in germicidal lamps the tube is not coated with a fluorescent phosphor. Rather than being made of ordinary borosilicate glass, which blocks shortwave ultraviolet light, germicidal lamp tubes are made of fused quartz or a special glass with high ultraviolet transmissivity. These differences combine to allow the 253.7nm shortwave ultraviolet light produced by the lamp's mercury arc to pass out of the lamp unmodified. (In ordinary fluorescent lamps the ultraviolet light produced by the mercury arc causes their internal phosphor coating to fluoresce, producing visible light).

Germicidal lamps also produce visible light due to other mercury radiation bands. The visible light output washes out and interferes with the perception of ultraviolet induced fluorescence, so a special quartz glass optical filter that is transparent to light at ultraviolet frequencies, but opaque to light at visible frequencies, is employed between the ultraviolet tube and fluorescent specimens. The ultraviolet-transmitting/visible-absorbing filter provides a 6" long x 13/16" wide window in an otherwise opaque cowl that covers the M100's ultraviolet lamp during operation.

The F6T5GL ultraviolet lamp has an average rated life of 4000 hours, which is approximately equal to five and a half months of continuous, around the clock use. The filter will also age and "solarize" (darken) due to exposure to ultraviolet light and has a rated life similar to the lamp. Assuming they turn their lights off when not in use, most M100 users are unlikely to exceed the rated life of their lamps and filters. Should you manage to wear yours out, or accidentally break your filter or shortwave tube, replacements are available from UVTools.

Stars are extremely powerful radiators of ultraviolet light. Our sun emits light across the entire ultraviolet spectrum, including the UVA (400-315nm longwave), UVB (315-280nm midwave), and UVC (280-100nm shortwave) bands. Fortunately for us, the Earth's oxygen atmosphere and ozone layer absorb all but a small fraction of the sun's ultraviolet radiation. It is the small fraction of the sun's ultraviolet light that makes it through the Earth's atmosphere that causes sunburns and genetic damage resulting in skin cancers. While man-made sources of ultraviolet light are many orders of magnitude less powerful than our sun, there won't be 93 million miles of space and 60 miles of atmosphere between you and an ultraviolet lamp. All ultraviolet light sources should be handled with caution, understanding and respect for their potential risks. While you can't see ultraviolet light, it can harm you.

The F6T5GL shortwave ultraviolet lamp is classified in Risk Group 3 per ANSI/IESNA RP-27.3-96. According to ANSI, "adequate protection should be provided by clothing, gloves, opaque materials, and ordinary window glass. Although this lamp will operate in standard fluorescent fixtures, it should not be used for general lighting applications."

The bottom line is you should exercise simple common sense and wear eye protection while using ultraviolet lights, and turn them off when handling specimens beneath them with your bare hands. Safety glasses made from polycarbonate plastic (Lexan) are effective optical filters for blocking shortwave, midwave and longwave ultraviolet light. A pair of polycarbonate safety glasses are included in the M100 kit. Adult supervision is required when children are handling and using ultraviolet lights.

While the majority of minerals that fluoresce under ultraviolet light exhibit the fluorescent effect under shortwave ultraviolet, there are some fluorescent minerals that fluoresce only under longer wavelengths of ultraviolet light, or fluoresce with different colors of visible light when exposed to different wavelengths of ultraviolet light. Compatible 307nm midwave and 365nm longwave ultraviolet tubes are available from UVTools for M100 users desiring to expand the spectral range of their lights. UVTools also offers an M101 kit, which expands the M100 shortwave kit reviewed here with midwave and longwave tubes and an additional fluorescent specimen.

Removing The Ultraviolet Tube From The M100 Removing the Ultraviolet Tube From The M100

Replacing or changing the tube in the M100 is a straightforward process. Access to the tube is obtained by unscrewing the battery cap and sliding the molded end piece with strap yoke off the light body, releasing the lamp cowl and filter. The bipin tube base is captured by spring loaded contacts. The tube is released by rotating it, similar to replacing a fluorescent tube in a shop light or ceiling mounted fluorescent light fixture. Reverse the procedure to reassemble the light.

M100 On Display and Photography StandPreparatory to viewing and photographing some fluorescent specimens with the M100, I fashioned a simple stand to hold the light from some scraps of 5mm (3/16") cabinet plywood I had lying about my shop. After cutting out the stand parts with a scroll saw and gluing them together, I painted the assembled stand with flat black spray paint.

The arms of the stand securely cradle and elevate the M100, positioning the filter on the underside of the M100 approximately 4 inches above the stand base. This simple accessory has proven a worthwhile and satisfying project.

Mounted in the stand, I can use the M100 to view specimens hands off, and the stand has already proven to be an invaluable accessory for doing fluorescent mineral photography. If you don't happen to have a scroll saw and some suitable scraps of plywood laying about in your shop, a serviceable stand could be engineered and fashioned from some heavy fluted cardboard.

[Switch to Visible Light]     [Switch to Shortwave UV Light]     [Longwave UV Light On]

Shown above left is willemite with calcite from the Huachuca Mountains, Arizona. At center is willemite with calcite from Franklin, New Jersey. On the right is calcite from Nuevo Leon, Mexico. These images were photographed under my M100 with a Nikon Coolpix 8000 digital pocket camera. Willemite with calcite from Franklin is among the brightest of fluorescent specimens and is ideal for demonstrating the phenomena of fluorescence with a shortwave ultraviolet lamp. Note the color change of fluorescent light emitted from the Nuevo Leon calcite under different wavelengths of ultraviolet light.

Reproduced below is the instructional guide included with the M100 and UVTool's 90-day warranty against defects in material and workmanship.

M100 Instructional Guide

UVTools Warranty

You can order the M100 Ultraviolet Lamp Kit from the UVTools web site. UVTools sources a wide variety of Ultraviolet lights suitable for educational, hobby and professional use. Check out the UVTools website for further information on their full line of ultraviolet lamps spanning the price and performance spectrum from their $9.99 M14 Longwave LED Kit to their $1250 W57 190 Watt Shortwave Ultraviolet Field Lamp.

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Bob Keller