Hi everyone, I have been trying, off and on, to set up my lab to do more oriented clay mounts, and I would like to do the filter paper method. One thing I keep running into is that after some minimal amount of clay is deposited on the filter paper, it just stops pulling any more liquid through. After trying a few different things, I’ve concluded that my roughing pump probably isn’t pulling a strong enough vacuum. It’s an Edwards E2M1.5, which is supposed to get down to a max vacuum of 2.3 x 10^-3 Torr. Does anyone with any experience with these setups have any idea how strong of a vacuum pump I need to get it to work well? It may be that my pump just isn’t working as well as it’s supposed to, so I don’t need to buy some ridiculously expensive turbo pump. Any advice about how to set it up, recommendations on pump models that seem to work well, etc., would be appreciated. Thanks! Barry Bickmore Professor of Geological Sciences Brigham Young University

On 9/6/22 5:31 PM, Barry Bickmore via MSA-talk wrote: > Hi everyone, > > I have been trying, off and on, to set up my lab to do more oriented > clay mounts, and I would like to do the filter paper method.  One > thing I keep running into is that after some minimal amount of clay is > deposited on the filter paper, it just stops pulling any more liquid > through.  After trying a few different things, I’ve concluded that my > roughing pump probably isn’t pulling a strong enough vacuum.  It’s an > Edwards E2M1.5, which is supposed to get down to a max vacuum of 2.3 x > 10^-3 Torr.  Does anyone with any experience with these setups have > any idea how strong of a vacuum pump I need to get it to work well? >  It may be that my pump just isn’t working as well as it’s supposed > to, so I don’t need to buy some ridiculously expensive turbo pump. >  Any advice about how to set it up, recommendations on pump models > that seem to work well, etc., would be appreciated. > > Thanks! > > Barry Bickmore > Professor of Geological Sciences > Brigham Young University     There's probably nothing wrong with your pump.  If it pumps down to a pressure of delta, then the pressure difference across the filter is (1 atmosphere minus delta).  A better pump, which might pump down to a pressure of 1/2 delta, (1 atmosphere - 1/2 delta) would not filter any faster.  But in any case, no pump can achieve a pressure less than the vapor pressure of water, as long as liquid water is present.     Unfortunately, for filtering clays, I have not found anything that beats patience. -- Rex Couture, Ph. D. Dept. of Earth, Planetary, and Environmental Sciences MSC 1169-204-110 Washington University in St. Louis 1 Brookings Dr. St. Louis MO 63130 Voice: (314) 935-4194 Fax: (314) 935-7361 rex@wustl.edu