A few years ago I was told that fine glass dust is used to keep the
coverglass from sticking to each other.  This was for automatic
coverslipping instruments.  

> ----------
> From: 	Gayle Callis[SMTP:uvsgc@msu.oscs.montana.edu]
> Sent: 	Friday, July 23, 1999 12:58 PM
> To: 	histonet@Pathology.swmed.edu
> Subject: 	Inquiry on clean coverslips needed
> 
> 
> >
> >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.
> 
>