DiVa nozzle salt volcano

In 31 years of flow cytometry I hadn't seen this before (although I  
don't get out much).  Lately we experience this phenomenon on our  
FACSVantageSEDiVa where, in the course of a few hours, the nozzle  
grows a salt volcano around the stream (I've attached a picture).   
This does not affect the breakoff nor the sort streams nor even the  
acquired data until the volcano grows high enough to impinge on the  
first laser.  It can also be removed easily by a wipe with a wet swab  
(although that's really inconvenient if the need arises during a  
sort).	Note: we are talking about a 70 micron nozzle running PBS as  
sheath at 30 psi - nothing fancy.

The question is: what causes it?  We *see* no leaks outside the  
nozzle tip but I'm wondering if the orifice has eroded and that's  
causing seepage.  Is there anyone who has seen this and/or has an  
idea of the cause?

Frank Battye.

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