Quote Originally Posted by holmburgers View Post
Here's a theoretical proposition... is there another liquid that would be easier to work with than mercury and more reflective than no mirror whatsoever?

The only thing that comes to my mind are the metals pointed to in the IBM's US 4054453 - mainly gallium that is.

Quote Originally Posted by holmburgers View Post
For instance, would there be an advantage in using water as opposed to no reflector at all. In the reflector-less, Bjelkhagen method (we'll call it), the reflection comes from the emulsion-air interface, correct?
Yes. For the history records, the "Bjelkhagen method" has been invented by Hermann Krone(1894).
I assume water won't work in this case because the index difference at the emulsion/water interface will be too small. If you want to dig further, I think the whole thing relates to Snell's law (see http://en.wikipedia.org/wiki/Snell%27s_law).