How to fix a warped shellac 78?

[marcapra]

I've heard that you can straighten a warped shellac record by putting it between two panes of glass and putting it in the sunlight for awhile. Do you need to apply some weight to the top pane? Or can you heat two ceramic tiles in the oven and them sandwich the record between the tiles outside of the oven to straighten it? How hot should the oven be? Should weight be applied to the top? And does this process damage the groove of the record?

[epigramophone]

I have used the glass and sunlight method successfully. I use two small plate glass doors, and the weight of the glass is sufficient to flatten the record.
The record must be 100% free of debris such as pet hair, otherwise it will be permanently embedded in the surface as it softens.
When the record is flat, move the entire sandwich indoors to gradually cool before trying to remove it.

[Gatyam]

As I recall, in one edition of his American Premium Record Guide, Docks described a method of placing the record in an oven. We tried it several years ago and it worked pretty well.

[52089]

Search the board and you will find pro and con discussions and other methods.

[soundgen]

I've heard that you can straighten a warped shellac record by putting it between two panes of glass and putting it in the sunlight for awhile. Do you need to apply some weight to the top pane? Or can you heat two ceramic tiles in the oven and them sandwich the record between the tiles outside of the oven to straighten it? How hot should the oven be? Should weight be applied to the top? And does this process damage the groove of the record?

I use two pieces of 5 mm glass 13" x 13" works a treat BUT you have to keep an eye on it it will melt completely and may even split , No sun not a problem use a 250 watt light bulb

[Curt A]

This glass method works just as well in the sunlight with only one piece of glass - this makes sure the temp doesn't get excessive...

[marcapra]

With one piece of glass, does the record go on top of it or below it? I have also seen a hair dryer used.

[Curt A]

With one piece of glass, does the record go on top of it or below it? I have also seen a hair dryer used.

The glass goes below... glass is used because it is perfectly flat and does not absorb any additional heat from the sun... On a sunny day, 20 minutes or so should do it. Glass on top and below might work, but you risk over heating the record, which is not necessary.

[mattrx]

I've used 2 pieces of glass in the oven. Clean the record thoroughly first. Set the oven temp to 170 and cook time to 10 min. Place the record sandwiched between the pieces of glass and leave if for a couple of hours in the oven. The oven will heat, but not too much, and when you remove the glass after all cools down, the record is ready to play.

I tried the sun and glass method a time or two and did not get the results I wanted. This method works quite well. The glass I use on top is about 13 inches square and about ½ inch thick (pill tile) for weight. I'm sure placing something on top of a thinner sheet of glass for weight would work as well. Setting temp to 170 doesn't get the record overly hot and with the 10 min cook time, it won't stay hot very long. I leave everything in place in the oven until it cools just to increase contact time of the glass to record. So far this method has worked many times over for me without a damaged record.

Matt

[Henry]

I've used this method with success on vinyl LPs, with 13"-square pieces of ¼"-thick glass in a 150º oven. I make the glass-record-glass sandwich, put it in the cold oven, and heat to 150º, then turn off the oven and let everything sit until the oven is cool---about two hours. Works every time; may also be repeated as necessary. As matrix says, cleanliness is crucial!