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Backlit Mosaic (HELP!) Answered

I've come up with a pretty cool idea for an artsy-type project, but I need a few sheets of acrylic. I need about 20" x 40" (~1m x .5m) of clear acrylic about 1/4" thick, and about half as much transparent black and opaque black (thickness doesn't matter). The idea is to make a backlit, tri-tone, grayscale mosaic, with 10cm square blocks. The transparent sheet will be the base, and needs to be 1/4" thick so I can put white LEDs around the edge (unless someone has a better idea). It will need some kind of frame to keep the light focused on the inside. Anyways, the main point of this post was to see where I can find acrylic sheets. Since it will be an inherently "pixelated" type image, I guess I could use smaller sheets of acrylic bonded together. Does anyone know where I can buy this? I would prefer to buy it locally so I don't have to pay shipping, but Lowe's and Home Depot don't carry it as far as I can tell. So there it is... my next project. I would love anyone's ideas, especially about using thinner sheets with LEDs, and ideas for a frame would be nice... Also, what's the best way to cut and bond the acrylic squares? Thanks Edit: added picture


Getting enough light from LEDs for a sheet that large would be difficult. You'd probably have more success with florescent lighting. Still, that large of a display might prove difficult. Build your lighting in a ventilated box at the base of the unit. The box would also act as support of the frame. I would create a reflective V of shiny metal (aluminum or steel) under the tubes and buff the lower edge of the plastic sheet (probably Plexiglas as opposed to more expensive acrylic). Then run aluminum foil around the right, left and top of the plastic to reflect any light back. Note that the glow wouldn't work as well with acrylic squares in front of the unit, but from something that would defuse the light from the surface of the plastic, such as grease pens or direct engraving of the sheet.

I'm really just looking for the white part to glow, with the rest just barely glowing when the room's lights are turned off or something... I was thinking about a wooden frame painted black, with a groove cut in it to house a string of LEDs going all the way around, and possibly a posterboard (shiny side) glued to the back or held by the frame to reflect light back off the wall and make it look white.