[78-L] Glass versus Vinyl

[Michael Biel]

I am not sure that the original questioner completely understood the 
difference between how a lacquer-coated disc and a vinyl pressing is 
made.  Lacquer discs are individually cut with a sharp stylus and 
material is removed to form the groove.  Glass was used as a supporting 
base between April 1941 and mid-1945 to replace aluminum which was a 
strategic war material.  Steel and paper fibre was also used.  Vinyl 
discs, like shellac and other similar materials, are pressed in multiple 
quantities in a hydraulic press from metal negative stampers.

So the question of glass vs vinyl makes no real sense.  Now if you want 
to ask about the use of lacquer coated discs for instantaneous recording 
vs. the use of solid vinyl blanks for instantaneous recording -- such as 
what Lennick mentioned as dub-plates -- now we have a question.  Vinyl 
can be either embossed or cut.  In the Victor pre-grooved discs and in 
dictating machines like SoundScriber, Gray Autograph, Edison Diamond 
Disc, and Dictabelts, the vinyl was embossed.  Because no material was 
removed the grooves are not necessarily permanent and the plastic might 
have a memory and return at least slightly if not completely to its 
original shape.  In any evcent, the plastic had a resistance and did not 
give a full fidelity recording.  When vinyl is used for cutting it is 
harder to cut than is the soft lacquer.  There were some German discs 
that were made of vinyl during the war years that were cut -- Decelith 
is one example -- but they are not as high quality as a lacquer coated 
disc.

For high quality disc mastering, lacquer coated discs are still used, 
and the supporting base is aluminum.  The only quality alternative is 
DMM Direct Metal Mastering which cuts a groove on a copper-coated disc 
using a high-frequency bias to enable the cutting of the metal.  
(Uncoated aluminum discs in the early 30s were embossed, not cut.)  
Vinyl Dub-Plates are not high quality enough to be used for professional 
mastering.

Now if the question is breakable shellac pressings vs. unbreakable vinyl 
pressings, that also is a completely different matter.  Vinyl discs 
would be ruined on heavy playback machines like acoustical wind-ups, and 
the material was initially more expensive than the shellac compounds.  
When lightweight pick-ups became common it was more used -- starting 
mainly with mass-produced pressed broadcast transcriptions in the 30s.

Mike Biel  mbiel at mbiel.com

On 1/6/2011 11:08 AM, David Lennick wrote:
> Vinyl, Victrolac, whatever, was also used for pre-grooved discs made by Victor
> in the 30s and 40s. The playback CAN be of decent quality if you can find a
> stylus wide enough..these weren't intended for professional or broadcast use.
> Some other plastics like celluloid were used for home recordings..again,
> nowhere near professional quality. I know of one instance where fiber based
> Presto discs (16 inch) were used for a program to be shipped and broadcast
> overseas by the CBC, and presumably they just didn't want to risk breaking
> it..it was a Gracie Fields Christmas program recorded in Vancouver but to be
> broadcast via short wave from Ottawa. The quality 50 years later was excellent.
>
> dl
>
> On 1/6/2011 10:35 AM, David Lennick wrote:
>> Two things are being intermixed here..glass replaced aluminum when it became
>> unavailable during the war. Vinyl was used for pressings, and rarely for discs
>> sold to consumers until it was economically feasible to use it and pickups were
>> lighter by the mid 40s. I've seen vinyl soft cuts from the fifties and I think
>> that's what's used today for "dub plates" but can anyone comment on the quality
>> of the 50s vinyl soft cuts? Noise level? Frequency range? Durability?
>>
>> dl
>>
>> On 1/6/2011 10:29 AM, marimbamoods at comcast.net wrote:
>>>
>>> just wondering - why were lacquer-coated glass-based transcription discs used well after the introduction of vinyl?
>>>
>>>
>>> i recently encountered a damaged glass-based disc from 1945, though vinyl discs were in use as early as ten or more years prior to that. given the fragility of the glass type, why were those manufactured at a time when vinyl was readily available?
>>>
>>>
>>> are the lacquer-coated surfaces somehow superior to the vinyl surfaces for fidelity or noise levels? that does not seem likely given the smoothness of vinyl, which continued in use for a half-century after its' introduction.
>>>
>>>
>>> so, why deal with the delicate handling issues of glass-based discs when hassle-free vinyl was already in use?
>>>
>>>
>>> best, david harvey