The Talking Machine Forum — For All Antique Phonographs & Recordings

When a chunk of plaster comes out of a cylinder, the celluloid is curved as if the plaster is there. However, over time, because the plaster isn't there to prevent shrinkage, the celluloid will tend to shrink and flatten. Replacing the plaster won't restore the curve, but it will prevent further shrinkage (good if the plaster has recently come out).

AudioFeline wrote:Yes, the depression is caused by the celluloid shrinking. I haven't come across any method to restore the original shape. However, filling missing chunks of plaster will prevent any damage becoming worse.

the celluloid shrinking is caused by the plasticizer evaporating , the plasticizer is camphor which is odd in that although a solid it has a vapour pressure without having to turn to a liquid , camphor is an oily solid and is readily available and low in price ,

if a small amount of camphor were to be smeared onto the inside of the cylinder where it has shrunk and held in place somehow with perhaps a latex balloon blown up in the cylinder > the camphor would migrate into the celluloid and perhaps reverse the shrinking , this may take some time but should work and when the celluloid has returned to its original state any excess could be wiped out and then immediately plastered to keep the new shape

soundgen wrote:

AudioFeline wrote:Yes, the depression is caused by the celluloid shrinking. I haven't come across any method to restore the original shape. However, filling missing chunks of plaster will prevent any damage becoming worse.

the celluloid shrinking is caused by the plasticizer evaporating , the plasticizer is camphor which is odd in that although a solid it has a vapour pressure without having to turn to a liquid , camphor is an oily solid and is readily available and low in price ,

if a small amount of camphor were to be smeared onto the inside of the cylinder where it has shrunk and held in place somehow with perhaps a latex balloon blown up in the cylinder > the camphor would migrate into the celluloid and perhaps reverse the shrinking , this may take some time but should work and when the celluloid has returned to its original state any excess could be wiped out and then immediately plastered to keep the new shape

I have wondered before whether this method would work...

- Bill

It would be worth someone experimenting with the camphor replacement idea and reporting back here.