Increasing the Illumination of Edge-Lit Carved Glass or Mirror
Author: Lon Weekly
Revised: August 03, 2005
I have been experimenting with various methods of increasing the edge lighting effect on pieces that I have carved. For purposes of these experiments, I used one of Jim Dowler's Lumi-Palette light bases with a 4" by 6" piece of 1/4" jade glass carved to a maximum depth of about 1/8". The image was a flower that occupied approximately 40% of the glass surface. I carved the same image in a piece of 1/4" mirror.
The results I got were similar with both pieces, except that the mirrored piece showed about 1/2 f stop more reflected light. I tried a number of different materials wrapped around the edge of the glass to reduce the amount of light that passed through it and into
the room. I got the best improvement with Silver Back Copper Foil, which is used with stained glass work. Its adhesive side is a matte silver color that evidently reflects the light rather than allowing it to emit.
When I used the 7/32" width tape wrapped entirely around the edge of the glass, except for a 3/4" gap which I placed over the LEDs in the light base, I got about 3/4 to one full f stop increase in reflected light right in front of the image.
I tried additional materials in back of the image to increase reflected light. I ultimately got the best results with BrightBak silver tape, which is used behind transparent glass in concrete stepping-stones for the same reason I'm using with carved glass. Compared to the edge-wrapped results above, I measured anywhere from 1/3 to 1/2 f stop increase right in front of the image.
Of course, these procedures would only work with a framed piece for aesthetic reasons, although the copper tape around the outer edge doesn't really look too bad. Once I get some of the LED arrays, I'll continue to do these measurements and post them for the group.
The items described above are:
VentureTape Silver Back Copper Foil (7/32" width). No. 1665
VentureTape BrightBak Silver Tape (2" width). No. 1820.
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