Degrading TV rubber masks.

[line sync]

I think many of us vintage television collectors have come across a crt mask which is badly cracked , melted , drooped or turned into a sticky mess.
This is becoming more of a problem as time goes by and the rubber slowly degrades so i,m asking if anyone knows of maybe a chemical / solution that could be applied to the rubber to make it last a bit longer.
The youngest of these masks are almost 70 years old and would never have been designed to last this long.
I have been doing some research into rubber and apparently all rubber will go this way eventually so we might have to get creative making masks ourselves out of wood or even moulding them.

[stevehertz]

I had one of the Pye 817 5" vision only sets that was restored at great cost by Philips for use at the Great Optical Illusion show at the Science Museum in London in the late 70s. They actually had three at the show for backup purposes. Gordon Bussey the then 'historic expert' for Philips oversaw the restoration of the sets, and the masks were carved from expanded polystyrene and then smoothed over with something like plaster of paris to get a good finish. Obviously this is nothing like the 'proper' rubber mask, but it looks good enough and it should last. Otherwise make one out of wood and use it to make a mould and then mould one out of silicon. A big job..

[G6Tanuki]

To me this looks like a good target for additive manufacture AKA 3D printing.

It would depend on the availability of an un-sagged rubber surround for scanning, and the identification of a suitably elastic material to render the new one.

[Panrock]

I recall one set I came across with the original mask stuck on to the tube, warped and 'melted'. I think this was a Murphy V136C. I basically painted on a new rubber mask over a period of several months, layer-by-layer, allowing setting between layers, with black roofing mastic.

This was a slow process, but there was plenty of time to make small corrections to build up the right shape.

Steve

[German Dalek]

Hi folks!

A better way, as far the mask is not melted away, is to use products from Voss Chemie.
https://www.vosschemie.de/en/

If melted, you have to rebuild one made of "play dough" or something like that. Then you can make a copy to produce a new rubber mask.

They are selling different kind of chemical products, even in small (household-typical) sizes.
For example, they are offering "molding compounds", if translated right.

You can use a dying mask to make a copy of it and with another product from this company you fill that material into the negative.
Therefor they are offering products made of different kind of rubber.
Their material is able to deal with undercuts!

Some of there products are available at:
https://www.yachtshop24.com/Vosschemie-Sicovoss-RF-Silikon-Abformmasse

The best is to contact them, and they give you an advice.

In the USA we had reproductions for the Motorola VT 71/73 models with the 7" CRT.
I bought 2 of them and they are good.

Regards,
German Dalek

[line sync]

Thank you to all for your comments.
Polystyrene and similar packing materials is a good idea steve , i am thinking that i could carve up this using a hot wire .
I do have a 9" mask made from aluminium and this would be ideal for the rubber moulding process but alot of masks wrap around the bowel of the crt and this would be a difficult mould to make.

Robin

[German Dalek]

Originally Posted by line sync

Thank you to all for your comments.
Polystyrene and similar packing materials is a good idea steve , i am thinking that i could carve up this using a hot wire .
I do have a 9" mask made from aluminium and this would be ideal for the rubber moulding process but alot of masks wrap around the bowel of the crt and this would be a difficult mould to make.

Robin

No, not with the material from Voss Chemie.
As I wrote above, they have elastic rubbers, which will deal with undercuts!

Regards,
German Dalek

[matspar]

Here's an approach I used on a Philips 383A last year.
First of all I cut a piece of thin 2mm white acrylic to fit over the front face of the mask, which was glued into place. Next I masked up the faceplate of a scrap CRM92 and mounted it vertically with some timber supports. This would maintain the correct profiles of the mask.
The sagged and damaged areas were then built up with decorators caulk, which maintains a degree of flexibility when cured and is overpaintable. Several applications and careful smoothing out needed. It was then sprayed grey with one of the the popular 'chalk' paints which provided an identical finish to how it was originally. Lots of patience required of course!

[line sync]

Nicely done matt.
I didn't think of using decorators chalk and nice to know that it sticks to the rubber ok.

Robin