I'm going to try this very soon.
(vacuum filtering mercury through my 60ml fritted filters leaves about 30g un-filtered,
as soon as air can pass around the central blob .)
PS In my specific case (mercury)
I'm now considering a near-fitting thin disk of ptfe or hdpe.
(tight fitting may be inconvenient to remove)
I'll try pe 'cling film' first.
[Edited on 30-6-2024 by Sulaiman]Rainwater - 30-6-2024 at 16:15
I get a similar problem with viscous materials. A thin sheet of plastic kitchen wrap layed on top of the buchner funnel does good but is prone to
ripping.