>
>After trying numerous supposedly-precleaned brands of coverglass, I have
>been using Richard-Allan coverglass for many years with satisfactory
>results.
>
>However, recently [24x50 rec'd in January, 24x60 rec'd in March] shipments
>of coverglass have been quite dusty-dirty in a peculiar way:
>there is a fine, almost powdery dust that doesn't show very clearly to the
>naked eye or on Brightfield microscopic illumination, but looks like a
>"starry night" on darkfield illumination!  This is a terrible problem for
>us, since 80% of our data analysis is done with darkfield illumination.
>Unlike dust I've encountered in the past, this cannot be removed with an
>airjet [or even cleaning with lens paper] while coverslipping.  A vigorous
>post cleaning of the dried slides decreases, but doesn't eliminate the
>problem on the surface, but the side of the coverglass sealed under the
>mountant still shows bright specks on darkfield, even after thorough
>drying.   I suspect that the problem could be from glass or silica dust
>produced in the 'sand blast technique' used to make some kinds of frosted
>end slides.  However, since I have yet to talk with anyone who actually
>knows the details of the manufacturing, that's just my best guess based on
>past experience.
>
>Richard-Allan admits that they have been having some problems with
>coverglass quality recently, even with their 'Signature' highest quality
>coverglass used for coverslipping machines.   In fact, the  replacement
>glass we received this week was the worst of all - some boxes show much
>dustiness to the naked eye.  They told me that the original Richard-Allan
>was bought out by Sybron [Cybron?] some years ago, and that they have not
>been manufacturing their own coverglass for 2-3 years.  Apparently, Erie
>Scientific who now makes Richard-Allan coverglass is the almost exclusive
>coverglass supplier to all brands sold in America.  One of our Brazilian
>postdocs suggests ordering the German coverglass [Kinittel Glaser brand]
>she used in her old lab, but her advisor says even that brand is only
>adequate, not great.
>
>So, before going on an all-out worldwide search for the perfect clean
>coverglass, I thought I'd tap the shared knowledge of the VIR newsgroup...
>Any words of wisdom, advice, sources of a better coverglass, etc. would be
>gratefully received!   I hope the problem can be solved from the
>manufacturer end without a great deal of time and effort on our part.  But,
>if Richard-Allan or other American coverglass doesn't improve soon, we'll
>be dead in the water on our most important research technique.  I know you
>can remove a lot of artefact in Photoshop for publication... but this too
>much.