the greatest amount of vacume that I can get using the hand pump
is 27 inches / -90 kPa , and at this vacume pressure the sides or surface of the flask is mostly covered by bubbles at this pressure.
if I agitate the flask then the larger bubbles float up and go out of solution , but new tiny bubbles form.
however if I strike the bottom of the flask against the bottom of a glass that the flask is sitting in , then thousands of tiny
bubbles stream up to the top !
if I continue striking the flask I keep getting the streams of thousands of tiny bubbles.
but the vacume pressure drops from -90 kPa to -80 kPa
at -80 kPa no more bubbles form even if I strike the flask.
ok I looked it up
my guage also reads kpa which at 30 inch guage
it is at -100 kPa guage.
the first stroke of the pump creates a -62.5 kPa vacume.
the second stroke of the pump creates a -82.5 kPa vacume.
the third stroke of the pump creates a -90 kPa vacume.
90 kPa is the highest vacume it can accomplish.
atmospheric pressure is 101.3 kPa
however 30 inch / -100 kpa can be exceded using a rotary vane pump and for higher vacume pressure a staged vacume pump
can be used.