Lightfader floor remembers where you were

While we’re on the topic of low-tech visualizers, here is another neat one. This Lightfader floor has a (presumably slow moving) fluid in it, that gets displaced when you step on it, and then slowly returns to it’s original state. This produces a footprint path that slowly fades away, without any electronics. It is a few years old, however I just became aware of it.

It kind of reminds me of what happens to your footprints when you walk down a beach, and then the waves wash them away. I’m guessing it is made of a thin layer of very viscous, tinted liquid. Think that would work, or does it have to be something more complicated? Perhaps some sort of liquid crystal-based polarizer, to improve the contrast? [via transmaterial]