Replacing Plaster on Blue Amberol Cylinders

[obmcclintock]

The easiest way for me to replace plaster in a blue amberol cylinder is to remold the new plaster on the cylinder drum itself on a working machine. I cover the cylinder drum with plastic wrap making sure that it is not creased or bunched up. Then I fill the void in the cylinder with spackle. I then slowly work the cylinder onto the drum. If I have a little too much plaster on it I find that I cannot push it all the way onto the drum so I remove it and some of the plaster and try again. When I have a good fit I start the machine and see if it is centered. If not I remove the cylinder and examine if the new plaster is a little to thick in that spot. If so I remove a little and try again. If it fits fine I leave the cylinder on the drum for 48 hours to dry thoroughly. I have always had good luck with this system. Other than the color difference between the new and the old plaster it is hard to tell that a repair has been made. Good luck.

[Phonofreak]

Spackle!!!! That's the word I was looking for. I was saying dry wall patch. I guess it's the same stuff. I never thought of covering the mandrel with a thin plastic bag. I'll give that a try the next time I do this.
Harvey Kravitz

[Curt A]

If you have an extra mandrel in your parts drawer, that would work as well... How about using a condom to cover the mandrel... (that way the plaster won't have any chance of clogging your reproducer)

[need4art]

Curt-that's exactly what I do-and yes you can use the cheap ones and if you are careful they will not break-and ya know if they do no one gets pregnant!!!-and oh yes I use the plaster of paris.
Abe

[AudioFeline]

All (or most for sure) of the Blue Amberol cylinders I have ever encountered over many years of collecting that have lost plaster have developed a slight depression in the celluloid that was supported by the missing plaster.

This slight depression in the celluloid surface created by the missing plaster often results in some audible distortion as the reproducer stylus navigates over this area in the celluloid.

Since the plaster was originally pressed into place inside the celluloid skin of the Blue Amberol cylinder I'm curious whether replacing the plaster using any of the aforementioned methods removes the depression in the celluloid from the missing original plaster.

Please accept that I'm not challenging any of these methods or substances used since I've never tried repairing or replacing plaster in any Blue Amberol cylinders I've purchased over many years. I'm only curious here.

In most instances I toss the cylinder out unless the amount of missing plaster is small enough that there is no resulting depression in the celluloid.

Doug

My hypothesis for the cylinder depression in the area of missing plaster.

First, some commonly known facts about the disks, as a foundation for the explanation. After the disk is manufactured, the plaster is stable (providing it's kept dry and the disk is cared for). The plaster keeps the cylinder in shape. However, it's fighting against the celluloid Amberol skin, which over time, will shrink. As the plaster is rigid and won't deform, the skin shrinkage will eventually result in a split along the cylinder's surface to release the buildup of shrinkage tension.

Now when a chunk of plaster comes from the core, it is not there to provide a force to resist the shrinkage of the skin. Therefore, in this area, the skin can shrink without resistance. This shrinkage will appear to be a deformation on the cylinder surface. As the shrinkage will try to create the smallest surface area, I would predict that over an extreme period of time the cylinder surface will become flat over the void created by the missing plaster.

Therefore, I would suggest that the "depression" cannot be fixed/repaired (unless a method is devised that will expand the celluloid back to it's original shape). It does suggest that further shrinkage (ie, flattening) could be prevented by replacing the broken plaster chunk as described by posts above.

One of the above posts suggests colouring the repairing plaster so it matches the original. Personally, I would prefer it to be a different colour compared to the original plaster. It will indicate a repair has been performed. If the type of plaster used displays problems in the future compared to the surrounding original plaster (eg. it expands or contracts at a different rate to the original, or becomes brittle), it will be easier for a future restorer to identify the problem area and address it (eg. by removing the repair and replacing it using a better version of the plaster filler). It's good conservation techniques being used.

[Herman]

All (or most for sure) of the Blue Amberol cylinders I have ever encountered over many years of collecting that have lost plaster have developed a slight depression in the celluloid that was supported by the missing plaster.

This slight depression in the celluloid surface created by the missing plaster often results in some audible distortion as the reproducer stylus navigates over this area in the celluloid.

Since the plaster was originally pressed into place inside the celluloid skin of the Blue Amberol cylinder I'm curious whether replacing the plaster using any of the aforementioned methods removes the depression in the celluloid from the missing original plaster.

Please accept that I'm not challenging any of these methods or substances used since I've never tried repairing or replacing plaster in any Blue Amberol cylinders I've purchased over many years. I'm only curious here.

In most instances I toss the cylinder out unless the amount of missing plaster is small enough that there is no resulting depression in the celluloid.

Doug

My hypothesis for the cylinder depression in the area of missing plaster.

First, some commonly known facts about the disks, as a foundation for the explanation. After the disk is manufactured, the plaster is stable (providing it's kept dry and the disk is cared for). The plaster keeps the cylinder in shape. However, it's fighting against the celluloid Amberol skin, which over time, will shrink. As the plaster is rigid and won't deform, the skin shrinkage will eventually result in a split along the cylinder's surface to release the buildup of shrinkage tension.

Now when a chunk of plaster comes from the core, it is not there to provide a force to resist the shrinkage of the skin. Therefore, in this area, the skin can shrink without resistance. This shrinkage will appear to be a deformation on the cylinder surface. As the shrinkage will try to create the smallest surface area, I would predict that over an extreme period of time the cylinder surface will become flat over the void created by the missing plaster.

Therefore, I would suggest that the "depression" cannot be fixed/repaired (unless a method is devised that will expand the celluloid back to it's original shape). It does suggest that further shrinkage (ie, flattening) could be prevented by replacing the broken plaster chunk as described by posts above.

One of the above posts suggests colouring the repairing plaster so it matches the original. Personally, I would prefer it to be a different colour compared to the original plaster. It will indicate a repair has been performed. If the type of plaster used displays problems in the future compared to the surrounding original plaster (eg. it expands or contracts at a different rate to the original, or becomes brittle), it will be easier for a future restorer to identify the problem area and address it (eg. by removing the repair and replacing it using a better version of the plaster filler). It's good conservation techniques being used.

In theory then I would think that for a really precious cylinder the following would be a possible solution:

Pour some epoxy that hardens in the void but not filling the complete depression. Clamp the cylinder at the ends between two sheets of rubber backed material to completely make the cylinder airtight inside the core. Have a schrader valve at one end. Apply compressed air to the valve thus creating an internal pressure that allows the depressed celluloid to expand to close to the original form. Allow epoxy to harden while maintaining the internal air pressure. After epoxy has cured then apply plaster to fill the remaining void to the original internal shape as suggested by the previous posts.

This is just me ranting early in the morning and not a proven method... LOL

[AudioFeline]

In theory then I would think that for a really precious cylinder the following would be a possible solution:

Pour some epoxy that hardens in the void but not filling the complete depression. Clamp the cylinder at the ends between two sheets of rubber backed material to completely make the cylinder airtight inside the core. Have a schrader valve at one end. Apply compressed air to the valve thus creating an internal pressure that allows the depressed celluloid to expand to close to the original form. Allow epoxy to harden while maintaining the internal air pressure. After epoxy has cured then apply plaster to fill the remaining void to the original internal shape as suggested by the previous posts.

This is just me ranting early in the morning and not a proven method... LOL

An interesting approach. But would the celluloid be flexible enough to expand reasonably quickly with the air pressure? As the celluloid is a hard substance and the shrinking causing the depression is essentially a chemical reaction due to the evaporation of the camphor, I would think that any pressure used to try to undo the depression would be more likely to break the celluloid. If it were possible, it would need to be done very slowly, and probably using a substance to add flexibility to the celluloid.

So my thinking is that a restoration of missing plaster can only prevent further shinkage/depression occurring, and it's probably not possible to repair any shrinkage. But I am willing (and hopeful) to be proven wrong with a non-destructive technique that does repair beyond restoration.

[Curt A]

All of this made me wonder... "Why are so many Blue Amberols missing plaster, mainly on the ends (at least in my experience)? Then it occurred to me... back in the day, how many people who owned cylinders and machines had reamers at home - probably not many, if any...

So, when the cylinders began to shrink and wouldn't fit the mandrels, an easy solution would be to whack the end on a table to remove some plaster to make them fit. I don't know if that is true, but it somehow makes sense to me, in the same way that when you run out of phonograph needles go find something similar and use a rusty nail...
That explains how so many popular records became worn out over time...

[AudioFeline]

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.

[NEFaurora]

Jerry, May I suggest creating a partial mold and trying oldtime White or gray "Squadron Molding Putty"...

Just a suggestion..

Tony K.

Edison Collector/Restorer )