Low cost Schlieren Visualization

Have you ever wanted to see air? A couple weeks ago I made an attempt using the difference between two images ... calling it a poor man's Schlieren imaging.
Last week, I managed to get a proper Schlieren imaging setup built for only $9 (not counting the cost of a DSLR camera). It worked well enough that the setup graduated to my website: DIY Schlieren Flow Visualization, and a youtube video with cool(?) music in the background.


This is a picture of the setup:

But really you should checkout the page on my website with the description here:

http://jonathan.lansey.net/pastimes/schlier/index.html