The standard way to identify the base material of a lacquer disc is  
to examine the disc's
center hole where silver metal (from an aluminum base), glass, or  
cardboard will be
visible. These bases also have distinctive sounds when the disc is  
struck gently against
its edge using an object such as a ring. An aluminum base yields a  
sound that has been
described as a "pong" while the glass sound is more of a "ping."  
Cardboard will, of
course, have no sound.

Casey, Mike. "FACET, The Field Audio Collection Evaluation Tool :  
Format Characteristics
and Preservation Problems, Version 1.0". Bloomington: Indiana  
University, 2007.

Marcos Sueiro Bal
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On Nov 19, 2009, at 15:00, Tracy Popp wrote:

> Ah, very interesting about the Diamond Discs... Having just  
> recently handled
> one myself I thought they were just a very thick shellac. Good to  
> know about
> the wooden core! I'm assuming these discs are then subject to the  
> same types
> of preservation concerns as other laminates - swelling/contraction  
> of the
> core, laminate peeling, etc.?
> Tracy
> On Thu, Nov 19, 2009 at 12:52 PM, [log in to unmask]  
> <[log in to unmask]>wrote:
>> Interesting observation about the "sound" a record makes when being
>> handled.
>> Not all instantaneous records are heavy. If they are paper  
>> substrate, they
>> will be much lighter. Glass and alum., heavier.
>> Getting into some esoterica here...Columbia 78s from a certain  
>> period are
>> laminated, perhaps not quite so heavy as a solid shellac. I have  
>> nevered
>> weighed either. Edison Diamond Discs are laminate over wood core  
>> and VERY
>> heavy (and thick), These are all commercially released records, not
>> instantaneous.
>> joe salerno
>> Shai Drori wrote:
>>> I never thought of this. It's sort of automatic to me and I guess to
>>> everyone else. The look and feel totally different,  that I never  
>>> spent a
>>> second thinking about it. Vinyl is light flexible has a certain  
>>> shine to it
>>> and almost no sound when you handle it. Shellac has this sound to  
>>> it when
>>> you handle it that sounds brittle, sort of like a "don't @#$^   
>>> with me". And
>>> instantaneous are very heavy compared to the others of the same  
>>> size. Of
>>> course there are exceptions to the rule but over time you sort of  
>>> just know.
>>> The last time I was puzzled by a record that felt "wrong" was a  
>>> few years
>>> back when I got a shipment of glass records. During the War  
>>> aluminum was
>>> gone to the army and different substances were used for the base,  
>>> glass
>>> among them. Never been more scared than handling those records  
>>> and that
>>> includes nitrate stuff. The up side was that they were ruler flat  
>>> and played
>>> on the emt like a dream, great sound.
>>> m2c
>>> shai
>>> Tracy Popp wrote:
>>>> Hello All,
>>>> I have a question on visual identification of, and  
>>>> differentiation among
>>>> shellac, instantaneous and vinyl grooved disks. Are there quick  
>>>> visual
>>>> and
>>>> non-destructive methods of determining the type of disk?
>>>> I am aware that most instantaneous have three "spindle" holes in  
>>>> the
>>>> center,
>>>> and one can generally determine that a disk is an instantaneous  
>>>> based on
>>>> the
>>>> core material (if one can see the core material.) Any other  
>>>> suggested
>>>> methods of quick ID and differentiation - barring cracking the  
>>>> edge of
>>>> the
>>>> disk to see the material composition? Is gently tapping the disk  
>>>> surface,
>>>> and listening for aural cues about material density an useful  
>>>> practice?
>>>> Thanks for your assistance!
>>>> Best,
>>>> Tracy Popp
>>>> UIUC Graduate Student MLS