Reflectors and Double Fixtures with

UVB Fluorescent Tubes

Reflector Tests     Spread Charts    Double Fixtures

Reflector Tests

The use of a reflector can produce a remarkable increase in UVB output at a basking spot. Even a piece of ordinary aluminium foil placed behind a fluorescent tube will significantly improve its performance, but if a reflector, such as the inexpensive clip-on type used for aquarium lighting, is fitted to a UVB tube it is possible to virtually double the output of the tube. The reflector effectively gathers a large percentage of the UV light from the sides and back of the tube, which would otherwise be absorbed by the walls of the vivarium, and redirects this forward into the enclosure.

We measured the output of a large number of tubes with and without a variety of reflectors including sheets of aluminium foil, home-made curved aluminium foil reflectors and commercially available reflectors such as the clip-on Arcadia Reflector (Fig. 2), which is available in a range of lengths to fit most tubes.

The results of tests carried out on fourteen different high-output tubes of various brands, lengths and ages, all fitted with reflectors, are shown in Graph 1.

When a higher UVB output is desired from a fluorescent tube the benefits of fitting a reflector are undeniable. As can be seen from Fig.3, the output of the tube is effectively doubled. One fairly new fluorescent tube fitted with a reflector may produce 30-40uW/cm2 at 12", ideal for rearing young lizards with high UVB requirements in small vivaria. And one fairly old fluorescent tube fitted with a reflector might be kept in use for slightly longer, when used for species with a lower UVB requirement. A 6-month-old tube emitting, for example, 14uW/cm2 at 12" with no reflector will produce a very satisfactory 24 or 25uW/cm2 at the same distance, if a reflector is fitted. Spread Charts Spread Chart 1 (below; described more fully in the main fluorescent test report) maps the output of one "typical" fluorescent tube, a new ExoTerra Repti Glo 8.0 tube, length 24", which had been in use for 12 hours. Spread Chart 2 (to the right) maps the output of the same tube fitted with an Arcadia Reflector. The way the beam is re-shaped and intensified in front of the lamp can be clearly seen.

If the spread chart is correctly scaled and superimposed upon a photograph of the tube in use in the vivarium, the way in which the UVB light is being distributed can be visualised. A comparison of Viv Chart 1 (featuring the tube in Spread Chart 1) and Viv Chart 2 (below) -in which a reflector has been fitted to the tube - shows the much-improved distribution of UVB within the vivarium; the whole body of the bearded dragon nearest to the lamp is now receiving moderate levels of UVB, not just his head.

Double Fixtures

Occasionally double fixtures - two fluorescent tubes mounted together - are used in larger vivaria. If all the necessary UVB is provided by one lamp, the other may be of a daylight type, emitting no UVB, but enhancing the colour balance and intensity of the visible light. Where higher levels of UVB are required, however, two UVB tubes may be fitted.

We have taken measurements from double fixtures both in the vivarium, and in a test situation, to measure their combined output, with and without reflectors. The results are very much what one would expect. Two tubes (with no reflectors) put out almost double the amount of UVB as a single tube. Two tubes, both fitted with reflectors, put out almost twice as much as one tube fitted with a reflector, and not quite four times as much as a single tube with no reflector.

We conducted two sets of experiments. In the first set, we used two new Zoo Med Reptisun 5.0 24" tubes controlled by a single electronic ballast, a Glomat 2 Double Fluorescent Lighting Control Unit from Rolf C. Hagen (UK) Ltd. The output of the tubes was measured when they were positioned separately and together, both with and without reflectors. (Figs. 4 - 7)

In the second set of experiments, we used two older Arcadia D3 Reptile 24" tubes controlled by two single magnetic ballasts, namely a pair of Arcadia Fluorescent Lighting Controllers.

The results for the first set of tests are shown in Graph 2 (below); the results for the second set were almost identical in terms of the effect of each combination upon output.

Care must be taken when using powerful combinations of tubes and reflectors. For example, whereas the single Zoo Med Reptisun 5.0 24" tube emitted 18uW/cm2 at 12", when two identical tubes were fitted with reflectors and placed side by side, the reading at 12" was 65uW/cm2.

This would provide a high level of UVB over a wide area, which might be suitable for some species, but too high for others. It would also produce a very large, very bright light source. For the comfort of the animals in the vivarium, this would almost certainly need to be directly above them, since if it were affixed to a side wall they would have no option but to look directly at its glare when facing that way. Certainly testing the double combination shown in Fig. 7 was quite unpleasant, owing to the glare, even though eye protection was worn.

The Fluorescent Tubes on Test

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Continue to the other Fluorescent Tube Survey reports:

The Fluorescent Tube Survey Results
THIS SECTION IS TEMPORARILY UNAVAILABLE as we are currently UPDATING THE RESULTS - OCTOBER-NOVEMBER 2010

The Use of Wire Mesh and Screens with Fluorescent Tubes
How much of the UVB is lost when the tube is behind a mesh screen?