Update Note: on July 4, 2013. I wrote a semi-detailed set of instructions for building the light box including a list of materials required at the link provided in this paragraph.
My intention to build a light box for tracing has started moving forward beyond planning. Over the last few weeks, I've been slowly thinking about the different issues involved and decided to build rather than buy.
Initially, I had to overcome a minor problem of finding a translucent sheet of acrylic to use for the tracing surface. The local hardware stores didn't have translucent acrylic but one of the plastic suppliers did. Tap Plastics listed a 1/8 inch thick sheet of translucent acrylic but that would flex too much so I had to come up with a way to strengthen it. The local Home Depot hardware store carried an 18x24 inch thick sheet of clear acrylic so I bought one of these to layer together with the thin translucent sheet. Not ideal for a solution to have two layered sheets but it was better than nothing.
So,a few days after picking the 1/4 inch clear acrylic sheet, I stopped by Tap Plastics. Turns out they had a 1/4 inch sheet of translucent acrylic but didn't advertise it. I'll return the clear acrylic sheet because I ended up buying the 1/4 inch thick translucent sheet. The translucent sheet was classified as 40 percent which indicates it should let a considerable amount of light through.
I built a box frame (excluding the bottom) which will support the drawing surface as well as house the light source. The frame was built from 1x8 pine and has a set of wood rails placed 1/4 of an inch below the top edge to position the acrylic even with the top edge. I still need to cut out a bottom for the box because the plywood sheet I bought was not big enough. I'll buy another thin sheet of plywood or hardboard when I return the acrylic to the hardware store.
You can see how the box looks as of current in the photo. The acrylic is still in its protective sheet to prevent scratching it while I trial-fit parts in place during the assembly process. The frame is nothing to look at aesthetically, but it's a tool that is more for functionality than form. My methodology is to build it quick and get it functional because I really could have taken advantage of it for my 2D art class.
The lighting source is still unresolved though. I wanted to use a 12 inch circular T9 fluorescent light as it would distribute the light throughout the box. Locating an affordable fixture has proven difficult with the cheapest starting at around 60 dollars. I stopped by a lighting specialty store to see if they had the adapters for fitting a T9 bulb into a traditional screw-base light socket but had no luck. I've seen them online for about 5 dollars so I order if I can't find anything locally. Hopefully one of the thrift stores will have an old fixture I can buy for a reduced price. But finding a T9 fixture is not so easy as it isn't a popular type of light tube. On a different note with the lighting, I also picked up a rocker switch at Radio Shack for turning the light off and on. I need to rig up a mount for it but that's not too difficult.
With a surface area of 18x24 inches (46x61 cm), the light box should provide enough room to trace reasonable sized drawings. This would have proved quite useful earlier before I started my 2D design art class. At several different points in time, tracing was a crucial part of the design process and the little light box didn't have enough space to even hold a standard sized sheet of paper. For tracing, an 18x24 surface area allows me to move things around or arrange multiple pieces for transfer to vellum. My plan is to use the old graphite-transfer method to go from the vellum(s) to an intended work surface. It does take up space but it can be stored on its side if I find a way to anchor the acrylic sheet in place so that it doesn't fall out when the light box is moved about.
That's the progress report for now. I'll post more pictures as the project develops. The next post in the series talks about how I'm adding a bottom to the box as well as wiring the lights. If you want to read about the project from the starting point, follow this link to the first post in the DIY light box series.