RUVA – what it means and why you want it

RUVA: Reflector UltraViolet A

RUVA: reflector uv curing lamp cutaway design

RUVA lamps are lamps that have a built in reflector. This image shows a cutaway, with a regular lamp on the left and a RUVA lamp on the right. The reflector is like a paint that is poured inside the lamp before the phosphors are added. The reflector in this image is a 180 degree reflector, where half the circumference of the lamp is reflective material, and light is emitted out the other half, kind of like how a flashlight only shines in one direction. The image shows that the light is reflected before it leaves the lamp, which makes it twice as effective as an aluminum style reflector. In general, you increase the UV output of any lamp by 35%-50% by using an internal reflector like this.

A reflector can be any size, although 180 degree and 210 degree (slightly more than half of the lamp is reflector) are the most common. I’ve personally set specs for lamps that had 120 degrees of reflector (the original SunMaster ReFlex series) and some that had 230 degrees. Theoretically, once you get over about 210, they are commonly called aperture bulbs or lamps. There are some that have about 300 degrees of reflector, so the light is all emitted through a small 60 degree slot. The smaller the slot, the more intense the output is, up to about the 300 degree mark. I’m currently designing some 230 degree aperture bulbs for prototype testing as I write this.

RUVA lamps emit light in just one direction, which is a plus for most application, but not all. One of the distinct advantages of a RUVA lamp is that it can often eliminate the need for an external reflector system altogether. Even on a good day, the shiniest aluminum is only good for about 50% reflectivity (the rest is absorbed/ionized as heat). When lamps are very close together, aluminum reflectors are basically worthless: The light gets ionized (or destroyed via wave cancellation) before it has a chance to strike the target, so the majority of light that is emitted away from the target is simply lost forever. Since over half of the light from a regular lamp will always shine AWAY from the target, we are talking about a lot of ultraviolet.

In some cases, an external reflector system can actually augment the built in reflector. The most obvious example is a guitar curing rig. The best ones are around 4′ x 3′ inside dimension, and use 16 FR71 lamps, all facing in (usually in a 5/3/5/3 lamp configuration). You can take spray glue, crinkle up some aluminium foil just a little so the light is diffused instead of hard reflected, and install it on the inside walls with the shiniest side facing the center of the cab. There is so much light bouncing around the cab (1600 watts worth in a 12 sq ft. footprint) that the foil is good for another 10%-15% or more. It can also be used at the top and bottom to get under and over the instrument with a little extra power. It isn’t required, but in some applications, the extra power pays for itself pretty quickly.

RUVA lamps also have slightly different heat characteristics, as the reflector seems to reflect infrared just as it does visible light an ultraviolet (UVA and UVB). This isn’t necessarily good or bad, it is just different. In one respect, it can be handy as the lamps tend to heat up quickly, so if you cycle the lamps a lot, it helps reduce cure times by a small but measurable amount of time. They produce the same amount of heat as a standard HO lamp, but they push a little more of that heat towards the target of exposure. In an open designed curing rig (the overwhelming majority of rigs are open design, unlike a tanning bed), it makes no difference to the target being exposed.

So why do you want a reflector? Because it adds 10% or so to the cost of the bulb, but increases the output by 50% in most applications and makes the design of most UV curing rigs much simpler. In short, it saves you money and reduces the time to cure. This is why virtually every bulb we sell for UV curing (or hydroponics use) has the RUVA system. We don’t make a non-RUVA version for price point advantage because we don’t want to build inferior lamps. If you need non-reflector lamps for some special application you can always call, you might be surprised at what we have in the labs at any given time. Most of you, however, want the RUVA system because it just makes life simpler, particularly for UV curing rigs that have only one row of bulbs instead of a surround-style design, like you would use for surfboards or curing other flat surfaces.

Dennis Brown