From: John Correia <jcorreia@biochem.umsmed.edu>
  To  : STAFFORD@bbri.org
  Date: Tue, 29 Aug 2000 08:56:41 -0600

Re: scratches on centerpieces

rasmbers

We have also experienced convection from scratches or more correctly
pitting on the sample side of a centerpiece - by being sure to turn the
cell so that side gets solvent, the problem goes away - in this instance
there are three indentations, or pits, equally spaced, that formed along
the base of the sector - inspection reveals many new centerpieces, we use
black epon, have similar marks that are smaller in size and frequency that
do not cause this problem, yet.   

My experience with scratches is if the scratch raises a burr above the
surface the sample will convect, but small scratches are usually not a
problem.

-------------------------------------------------------------------
 Dr. John J. "Jack" Correia
 Department of Biochemistry
 University of Mississippi Medical Center
 2500 North State Street
 Jackson, MS  39216
 (601) 984-1522                                 
 fax (601) 984-1501                             
 email address: jcorreia@biochem.umsmed.edu     
 homepage location: http://www2.umsmed.edu/dept/biochemistry/correia.html
 
 dept homepage location:   
http://www2.umsmed.edu/dept/biochemistry/biochem1.html
-------------------------------------------------------------------