The heart of the tabula rasa is a wooden sandbox with a tightly streched fabric. You can imagine it as a back of a paint canvas. The gap between the fibers are large enough for light and air to pass through, but small enough to hold sand particles.
A hidden wide angle camera is pointed at the sandbox from below. We were able to create a custom software to record drawings in the sand, relying only on the ambient light penetrating the thin sandbox. The results are suprisingly accurate.
In order to 'reset' the canvas, the sandbox is mounted on a pair of hidden rails. An electric motor perodically shakes the sand-tray (think etch-a-sketch) and renders the sandbox clean. Finally a motorized airprobe is used to 'blow' the sand from below, thus create create the illusion of drawing. Care had to be taken for all these components to reliably work together. The combination of fabric and sand, the right about of air pressure and the right head movement took numerous attempts to get right, but it was worth it. The result is a trully magical experience, a seamingly invisible finger creating sand drawings.
In thename of sustainability, the first prototype of tabula rasa was largely build of reclaimed components. The wooden parts are reclaimed ply wood, while most of the electronics are out of used printers and scanners.
For more information about the project and the process, you can download the pdf booklet here.