[78-L] Glass Compound 78s

[78records at cdbpdx.com]

THANKS for all the info about these.  Very helpful.

The link below shows the label of one of the records I am inquiring about.  You can see an under-label around the edge of the studio label.  Is that label familiar?  

http://78records.cdbpdx.com/BCO/tn-800_BCO-07_SentForYouYesterday.JPG

When looking through this record, it is blue, as described.  I have some records that are stamped GLASS on the label and they are red when I look through them.  See link below:

http://cdbpdx.com/78records/Labels/tn-600_RadioRecorders_5-31-44_SeeThru.JPG

I am keeping them in a 10 page record album.  Guess I'd better make other arrangements for them.

Thanks!  CDB


--- On Mon, 6/15/09, Michael Biel <mbiel at mbiel.com> wrote:

> From: Michael Biel <mbiel at mbiel.com>
> Subject: Re: [78-L] Glass Compound 78s
> To: "78-L Mail List" <78-l at klickitat.78online.com>
> Date: Monday, June 15, 2009, 10:14 PM
> 78records at cdbpdx.com
> wrote:
> > > Greetings. I am wondering how to easily identify
> glass compound 78s.
> 
> I assume you are referring to a glass-base lacquer coated
> recording
> disc.  This is a disc that is a sheet of glass with a
> plastic coating on
> it that the recording is directly cut into.  
> 
> > > I was playing a record from 1942 and I noticed
> the sunlight was sparkling
> > > off the record in a rainbow of color, as if the
> light was being reflected
> > > through a prism.
> 
> This could happen with an aluminum base lacquer disc as
> well because
> that base is reflectively shiny as well, but when you
> describe it being
> translucent you can only be describing a glass base disc. 
> 
> > > I examined the record closely and discovered I
> could see brightly lit
> > > images through it. It has an unfortunate crack
> and the edges of the
> > > crack seem to be flaking off like glass. 
> 
> The lacquer coating can flake off like this from any base
> material,
> aluminum, steel, or glass.  The dark coating is not
> itself glass.  If
> part of the clear glass base is crumbling, then the base is
> more than
> just cracked, it is smashed.
> 
> > > Could this be a glass compound record? Are there
> any sure-fire
> > > ways to identify glass compound records besides
> cracking them
> > > and looking to see if the edges are flaking
> off?  Thanks! CDB
> 
> As dl mentioned, you often -- but not always -- can see
> light shining
> thru the translucent discs.  If you do not want to
> hold the disc up to
> the light, you can shine a strong light up thru it. 
> Once you have
> identified a glass-base disc it should always be stored in
> a sleeve with
> a second aluminum-base disc with it, and the disc handled
> only with that
> second disc supporting it.  Archives with large
> collections of glass
> base discs should have a rule that an aluminum disc be slid
> into the
> sleeve and both discs be taken out together.  I was
> lucky when I worked
> with the NBC Chicago collection at Northwestern to have a
> large amount
> of unimportant aluminum based discs to store with our
> glass.
> 
> As dl mentioned, professional grade discs were not marked
> on the discs
> themselves, only on the sleeves which often can get
> switched so that a
> glass base sleeve could house an aluminum disc, but most
> home-grade
> glass base discs are marked on the manufacturer's
> label.  But glass was
> rarely sold to the home recording market.  They used
> steel base and
> fibre base discs.  Many radio and recording studio
> labels did mark the
> discs as glass, but not always because the labels were
> sometimes
> prepared by a secretary, not the recording engineer. 
> The first glass
> Presto discs were very thick and had a metal grommet in the
> center hole.
>  AudioDevices' AudioDisc brand had a fibre-center that was
> about
> 2-inches in diameter, and the edge of how this fits into
> the larger
> glass hole can sometimes be seen or felt.  Later in
> the war Presto had a
> printed label that said glass base, but I am not sure if
> the discs were
> shipped with this label on them or if it was to be applied
> by the user.
> 
> As to whether glass discs were more flexible when new, I
> doubt that
> because one of the reasons glass was used was because it
> was less
> flexible than aluminum.  One of the selling points of
> glass prior to the
> war was that it was ideal for use for mastering because it
> remains
> flatter than metal when being electroplated.  The
> first glass discs were
> shipped in early April 1941, prior to our entry into the
> war, and before
> aluminum rationing.
> 
> Mike Biel   mbiel at mbiel.com
> 
> -------- Original Message --------
> Subject: Re: [78-L] Glass Compound 78s
> From: David Lennick <dlennick at sympatico.ca>
> Date: Tue, June 16, 2009 12:25 am
> To: 78-L Mail List <78-l at klickitat.78online.com>
> 
> Very simple..assuming that it's sturdy enough for you to
> handle without
> it 
> breaking (and those things are VERY thin), hold it up to
> the light. If
> you see 
> translucent bluish, yep..it's glass based. As for the
> flaking, that's
> not 
> reversible.
> 
> If you find this somewhat risky, you can tape the edge
> lightly with your
> ring 
> finger. The sound will be different from tapping an
> aluminum disc.
> 
> Not all manufacturers identified glass lacquers, except on
> the sleeve,
> which 
> was pretty dumb. Amazing that 65 years ago, these things
> were able to be
> 
> shipped..carefully, yes, but they frequently made it
> intact. They must
> have 
> been a bit more flexible when they were new.
> 
> dl
> 
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