Gary,

While I agree that for high-magnification critical microscopy and
photography a glass coverslip will be the best, for surgical pathology
and the vast majority of microphotography the tape is just fine. I used
this method for several years in a past job and nobody complained about
it. I was hesitant to use it but the fact is that even a very fussy
pathologist who publishes practically daily never even noticed when we
changed to the tape. So, for practical purposes in a heavy-workload
pathology lab the tape is fine. And I doubt that glass coverslippers
will ever match the speed, which is the tape machine's primary
attraction.

Tim Morken, B.S., EMT(MSA), HTL(ASCP)
Infectious Disease Pathology
Centers for Disease Control
MS-G32
1600 Clifton Rd.
Atlanta, GA 30333
USA

email: tim9@cdc.gov
       timcdc@hotmail.com

FAX:  (404)639-3043



----Original Message Follows----
Date: Tue, 26 Jan 1999 13:25:19 -0500
From: garygill <garygill@dcla.com>
Subject: RE: Mercedes Coverslip Tape
To: "Hagerty, Marjorie A." <mhagerty@emc.org>,
 'Histonet' <histonet@pathology.swmed.edu>

Marg:

	It sounds as though you already have a Sakura machine and you're simply
price comparison shopping.  If you don't already have a Sakura tape
dispenser, however, please read my post below that was originally
submitted
to Histonet 1/7:

	Cover glass acts the first lens in any microscope objective, and is so
considered by lens designers.  There are specific refractive index,
dispersion values, planoparallelism, and thickness specifications for
cover
glasses that plastic cover glasses can not match.  It is not enough that
a
specimen, whether cells or tissue, be covered by something thin and
transparent.

	Most often No. 1-1/2 thickness cover glasses are recommended in
publications.  Such recommendations are based on the interpretation of
the
thickness printed on the objective itself (e.g., 0.170 [meaning 170
micrometers thick]).  art of the cover glass.  No. 1/1-2 thickness cover
glasses are correct only when there is little or mounting medium between
the
specimen and the underside of the cover glass (e.g., cells grown on a
cover
glass, specimen mounted on a cover glass, spring-loaded clothes pins or
weights applied to the cover glass to squeeze out the excess mounting
medium).  Such applications are research oriented and not practiced
routinely.

	In practice, the thickness of mounting medium between the specimen and
the
underside of the cover glass is often substantial and acts optically as
though it is glass.

	Many years ago some authors actually cross-cut some histo slides and
measured the thickness of the mounting medium, finding it to be
substantial
relative to allowable deviation tolerances.  The upshot of all this is
that
No. 1 thickness cover glasses should be used routinely.

	4X and 10x objectives are insensitive to cover glass thickness, due to
their low numerical apertures.  40X acrhromat objectives can tolerate
deviations only as small as 15 micrometers.  What happens when overly
thick
mounting medium and cover glass are applied?  GLARE.   High dry image
quality loses contrast, appearing cloudy, hazy, washed out, etc.  The
greater the thickness, the worse the appearance.  The cleaner the
microscope, the closer it is set up for Kohler illumination, the higher
the
quality of objective (e.g., planapochromat), the more obvious the loss
of
contrast appears.  If one practices sloppy microscopy, the loss of
contrast
will be less obvious.  Is the loss of contrast ruinous?  Will it prevent
one
from making a diagnosis?  No, but plastic tape is a triumph of
technology
over technique.

	Bottom line:  Sakura plastic tape can not equal glass cover glasses
applied
by any man or machine.  However, if saving money is your primary
goal...?
At one lab where I worked, the Sakura machine was sometimes used,
sometimes
not.  The surface of the mounted tape was wavy, and often pulled up at
the
edges.  High dry microscopy of cells along the edges was often
impossible.
Some dotting inks used in cytology etch the plastic and can not be
removed.
Also, the tape scratches rather easily, further scattering light and
introducing glare.  Cytology preparations are less forgiving than are
histo
ones.

Gary Gill

-----Original Message-----
From: Hagerty, Marjorie A. [mailto:mhagerty@emc.org]
Sent: Tuesday, January 26, 1999 12:25 PM
To: 'Histonet'
Subject: Mercedes Coverslip Tape


Hi All,

Does anyone know anything about the coverslip tape from Mercedes
Medical? They have tape for the Sakura coverslipper that costs less than
the tape from Sakura. I am interested to find out if anyone has tried it
and how they liked it.

Thanks,
Marg
EMC






______________________________________________________
Get Your Private, Free Email at http://www.hotmail.com