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Straigtening warped 78s
http://forum.talkingmachine.info/viewtopic.php?f=3&t=34862
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Author:  Swing Band Heaven [ Sun Apr 15, 2018 4:46 pm ]
Post subject:  Re: Straigtening warped 78s

Does anyone know if there is a safe way to flatten laminated disks?

S-B-H

Author:  phonogfp [ Sun Apr 15, 2018 5:54 pm ]
Post subject:  Re: Straigtening warped 78s

If a laminated record such as Columbia were put between the glass plates, put into the oven at room temperature, then brought up to 175 degrees, I don't understand why it would be any more at risk than a solid disc.

Please educate me, as I wouldn't have hesitated to do this with a laminated disc.

George P.

Author:  CarlosV [ Mon Apr 16, 2018 2:56 am ]
Post subject:  Re: Straigtening warped 78s

phonogfp wrote:
If a laminated record such as Columbia were put between the glass plates, put into the oven at room temperature, then brought up to 175 degrees, I don't understand why it would be any more at risk than a solid disc.

Please educate me, as I wouldn't have hesitated to do this with a laminated disc.

George P.

The only fragility I see in laminated records is the difference in thermal expansion between the layers (paper and shellac). This creates tension between the layers and may create wrinkles and superficial cracks. The difference in moisture absorption between these layers also creates such stresses, but some experimentation would be required to figure out which of them is the most important environmental factor.

Author:  phonogfp [ Mon Apr 16, 2018 8:40 am ]
Post subject:  Re: Straigtening warped 78s

CarlosV wrote:
The only fragility I see in laminated records is the difference in thermal expansion between the layers (paper and shellac). This creates tension between the layers and may create wrinkles and superficial cracks. The difference in moisture absorption between these layers also creates such stresses, but some experimentation would be required to figure out which of them is the most important environmental factor.


Agreed, but bringing the temperature up gradually (starting with a cool oven) should minimize any expansion differential, shouldn't it?

I'll need to dig out a junk Columbia and try this.

George P.

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