Schlieren setup diagrams by Professor Vandiver (click on thumbnails for PDF File):

An article on Professor Vandiver's work with schlieren photograhy from Scientific American, August 1974 (click on thumbnails for PDF File):

To learn more about schlieren theory look at this recent text:
Settles, G. S. Schlieren and Shadowgraph Techniques: Visualizing Phenomena in Transparent Media. Springer Verlag, 2001.