From: Jeffrey A. Cohlberg <cohlberg@csulb.edu>
  To  : RASMB@bbri.harvard.edu
  Date: Fri, 18 Dec 1998 10:23:00 -0700

followup on window liners

Dear RASMB folks,

This is a followup to the message which I posted last week.  At Tom
Laue's suggestion, I contacted Allen Furst at Beckman 
(afurst@beckman.com), discussed the problem with him, and sent him a 
couple of my liners.  I also forwarded copies of the e-mails I received 
from several of you who also indicated that you were having problems 
with window liners being too thick.

Allen has now responded:

" I've checked our manufacturing records and found that there has been
no change in the materials used in the product for the past 6 or 7
years, but it is a different product than we used to ship with the Model
E.

I looked at the liners you sent and tried them in my lab. They were,
admittedly, a bit tight. I placed them flat upon the bench and rolled a
cell back and forth over them a few times, to round them. After this, it
was not too difficult to fit them into my window holders. After one
spin, they will compress and go in more easily....

The product is not defective. Indeed, if the liners were much thinner,
after the compression of first use they would not immobilize the windows
effectively and some leakage might result."

I tried this.  The old window liners were 0.0130 inch, while the new 
ones were 0.0150 inch.  After repeatedly kneading a liner, using a cell 
as a rolling pin, I managed to get the thickness down to 0.0140 inch.  
At this point, I could get the window into the holder.  It was still 
very snug and harder to use than the old ones, but it was not nearly so 
tight as before.

I plan to try to locate a sheet of 0.0130 inch phenolic, which should 
run around $3 a square foot.  If I can find it, I'll be happy to send a 
piece to anyone who wants one.

Thanks to everyone who replied to my posting, including Claus Urbanke,
who indicated that he makes his own liners out of PVC sheets about 0.3
mm thick and replaces them after each run.

Jeff Cohlberg

-- 
Jeffrey A. Cohlberg, Professor
Department of Chemistry and Biochemistry
California State University, Long Beach
1250 Bellflower Blvd.
Long Beach, CA 90840
phone (562) 985-4944	fax (562) 985-8557