Chunk,
This process is one of those "real old process", it dates back to about 1850 to 1880 something. Basically, you coat a sheet of glass with light sensative chemicals and place the coated sheet of glass, while it is still wet and dripping into a film holder. The exposure times are usually a few seconds long, if you noticed in the color photograph there is a brace behind that you would help steady the person. The ASA for film like this, is "about" .25.
My friend can tell you a whole about this than I can, but if you did a search on colldion, wet plate or ambrotype, you'd get a good feel for it too.
Brian