[78-L] dewarping 78s

[Steven C. Barr]

----- Original Message ----- 
From: "Alexandre Benoit" <pathe90rpm at yahoo.fr>
> Dewarping 78s at 100 degrees celsius? Says Steven Barr. That's 212 
> Fahrenheit.
> Far too hot!
> The compound starts to get flexible at 80 degrees C, that's 176 
> Fahrenheit.
> The risk to get the groove walls involved is too high in anything above 
> that.
> I am talking from experience. And I measure the actual temperature (with a 
> meat thermometer the results of which I have cross-checked with other 
> thermometers).
> I like to have control over the result, therefore I don't dewarp with heat 
> from the sunshine.
>
That was a GUESS! As I noted, my experience with warped shellac records
was "by accident"...the records (left on the front seat of a '58 Impala 
convertible)
had become warm enough to "bend" to match the contours of the seat...but, 
when
I found them, were still flexible enough to be manually "bent into 
flatness!"

I had the same thing happen when I accidentally placed a milk box partially
full of 78's in front of a heat register! A group (c.60?) of 78's became 
soft
enough to bend; however, when I found them, they were still flexible...and
as such could be bent into "flat"...!!

OTOH, vinyl discs EXPAND in increased temperatures...this resuts in
LP's/45's developing UNcorrectible warps, since the warps have to
accomodate the increased amount of now-expanded vinyl!!

Steven C. Barr