Re: Sorry to ask again but...
There are many different kinds of flatbed scanners and I don't know where the place of best focus in on all of them. However, all of the ones I have used appear to have the point of best focus not on the surface of the glass of the scanner but at somewhere around .5mm to 1mm from the top. That is suggested by various film holders themselves. Therefore, placing a thin piece of glass on the top of the scanner, with the emulsion of the film placed in contact with that glass, appears to place the negative at a point where the focus is at least as correct as with the negative holder. Another issue is that lenses used in scanners appear to have really great depth of field and small differences in placement don't appear to make much difference. In any event, with the Epson 4870 I definitely see a small improvement in a scan made fluid mounted on glass as opposed to either placement over the glass in a holder or placement emulsion side down dry over the scanner glass.
As for the dry mounting fluid, some of the stuff being used today is solvent and simply evaporates from the film so that little or no clean-up is necessary. Kami mounting fluid, for example, leaves little or no residue. However, if the mounting fluid drys out during the scan you have pretty much lost the advantage of dry mounting so for scanning large format negatives at high resolution I use prefer Johnson's baby oil since it is more viscous and does not dry out as fast. After scanning I simply place the negative in a tray of warm water with a little liquid dishwater liquid and let it soak for a few minutes, then rinse it briefly and hang to dry.
I will look for that story about Clemson in the Times. Last time I remember Clemsion making much of a splash in the Times was when it was ranked the #1 or #1 party school in the USA. I see that Clemson did not make the top 30 in that category this year, though they finally got into the top 30 of public universities. I hope that neither of those rankings has anything to do with fact that both Sam and I retired this year!
Is there a limit to dumb questions -- or do we get an unlimited supply?