I recently "proofed" some baker's yeast, to compare some I had used in bread
that had
failed to rise, with some "fresh" yeast that worked.  After observing the
difference in gas
production and general "foaming" I examined some of the water/sugar/yeast
"slurry" under
a microscope but could not observe anything at 400x, except what appeared to
be small
bubbles.  I was anxious to actually see the little yeast guys (as were my
kids).  I used a cover
slip over the slurry, and the bubbles seemed to stop forming soon after.  Is
400x enough, and
is the cover slip depriving the yeast of oxygen that it needs to keep
forming gas?
Thanks/ Curtis Crowell