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[Paul Koning]

>>>>> "woodelf" == woodelf  <bfranchuk at jetnet.ab.ca> writes:

 woodelf> I guess you have two kinds of bubbles 1) Trapped air 2)
 woodelf> Voids in the filling.  

If you do the pouring in vacuum, and the viscosity is not excessive,
you shouldn't have voids -- because those tend to come from trapped
air and you get that in vacuum...  (That assumes you got the bubbles
out of the resin, of course.  Same comment there: mix in vacuum?  Then
all you have left is reaction gases, which resins meant for casting
shouldn't produce.)

 woodelf> I vacumm pump may be $$, but a
 woodelf> reversed air compressior pump or other hacked pump may work
 woodelf> since I don't think you need a strong vacumm.  

A water jet pump -- as found in old style chemistry labs -- produces a
surprisingly good vacuum.  It's very simple, no moving parts.  You can
find them in waterbed supply stores -- the widget used to empty
waterbeds is one of these things.

Rule of thumb for jet pumps: the minimum pressure achievable equals,
roughly, the vapor pressure of the working fluid.  

   paul