Bubbles in the water bath are, after all, just dissolved air being
released and sometimes becoming trapped under sections.
If the water to be used is first boiled to remove most of the air and
then placed in a bottle filled to the top and then tightly stoppered
this will eliminate most of the problems.
An Ultrasonic bath will also remove bubbles and we used to use this
method all the time to eliminate bubbles from epoxy solutions in EM and
to get chemicals into solution. It is a bit noisy, but it strikes me
that a water bath equipped with ultrasonic mechanism would be of
advantage (I'll give my address for any royalties later). Have to make
sure that don't put it on when delicate sections are floating in the
water bath.
When air is trapped under sections, sometimes this is the result of
potential folds in the section. Floating sections on dilute alcohol
(5-10%) or Reuters solution, before floating in the water bath usually
eliminates this. However, if there are any tears, have to be careful
that the alcohol does not get onto the upper surface of the section and
cause the surrounding tissue to sink under the water.
Barry