Two types of pastes were used in Poland, based on nitrocellulose and methacrylate gum. Barium, strontium and calcium carbonates were mixed in binder. Appropriate diluents and plasticizers were also added. Thus, depending on the used binder, the products of decomposition during the formation of the cathode were: carbon dioxide, nitrogen, water vapor or carbon dioxide, water vapor. Some carbon monoxide may have been formed as well. In Polish picture tubes, only getters based on a metallic barium were used.
In the residual gases, methane appeared as the dominant gas in the pumping out and gettered picture tube.

There has been an update to the progress of a CRT re-building effort.
This was was added to the ETF website several weeks ago.
I hope I am not overstepping by posting this here. I would have thought he would have added to the thread here himself.
https://www.earlytelevision.org/nick..._5-1-2022.html

Thanks for posting this!

Yeah, thanks! I had kinda given up on progress. Good to see it moving along.

Re: the cathode materials; the information I find is the currently used mixture is 56% BaCO3, 31% SrCO3, and 13% CaCO3 by weight. Then mixed with nitrocellulose lacquer in the proportion of 44% carbonates and 56% lacquer. In the past it was usually Ba and Sr carbonate; the Ca was added later because it was found to improve emission current.

What happens when a tube loses vacuum is the oxides combine with water vapor in the air and form hydroxides, The reaction is reversible under vacuum and with heat, but does not result in a working cathode again for some reason.

During activation, the carbonate compounds reduce to oxides, giving off carbon dioxide, plus whatever gases the lacquer breaks down into. Ideally this process is carried out while still under pumpdown to get those gases out of the tube prior to sealing and getter flashing.

In Poland, completely different proportions of carbonates were used. When heated, hydroxides melt and run off the core. This is supposedly the main cause of bad emissions from air-entrained cathodes.

Out of curiosity, why were they using a different material overseas? (Which also brings up the question - did other vendors over there use different compositions for everything?).

I know Beryllium phosphors were used in fluourescent bulbs in the US until just after WWII, and they were also used in some projection tubes in the US. Did they ever see use overseas in either application? And if so, when did the practice end?

I suppose in general there were many variation of things such as compositions.
Large companies like RCA, Sylvania, etc. could afford to research things. Patents on some things could cause some manufacturers to come up with variations. Company secrets in other words. Coca-Cola and Pepsi-Cola.
Other countries had other large companies and even universities did some research.
The cost and availability in different areas could also effect the formula what was used.

This is fantastic. I hope his enthusiasm has persisted since the posting. If this ever gets up and running, I'll be in line for several rebuilds regardless of the outcome. Whatever it costs, I want to support it! I was so down when I saw the late 2018 posting the project had been abandoned. It may still be on life support but I'm keeping fingers and toes crossed!

Fantastic indeed. Just to make it clear the museum does have all the equipment and dedicated space for rebuilding. Nick has his own similar setup at his place. So we have two complete rebuilding facilities. Two main issues remain, skilled operators and a supply of guns.

I attended the vintage computer fest Midwest recently and there is a growing need for monitor rebuilding in that community as well. There is also the vintage arcade gaming contingency. I think there is a huge potential to join forces.

ISTR the museum acquiring a large stock of inline guns with some of their equipment. If they had someone to do the work they could probably make good money rebuilding color monitors for the arcade and vintage PC communities. When a PC or arcade is worth 4 figures it's a lot easier to justify spending $200-500 on a rebuild of the CRT.

Long overdue update!

Since most of this work will likely revolve (no pun intended) around smaller size tubes like the 10BP4 and 12LP4, I decided to throw together a smaller glass working lathe. This is being build out of scrap from an aluminum pallet and of all things an elliptical machine. The rotating bit was attached to the elliptical pedals to make them go around, turned out to be a great basis for the CRT portion of the machine. I just attached a round piece of aluminum to it, and that will spin the tube once I get a way to hold them ironed out. Plan is to have a speed controlled motor mounted underneath with a jackshaft to run both ends (the gun holding end must spin at the same speed as the tube), I already have the torch ready to go once this part is finished.

https://videokarma.org/attachment.ph...0&d=1701554386

I am glad to hear that you are still active with this project, Nick. I wish you much success.

This hobby definitely needs someone in the rebuilding business.

Will you still he able to do larger black and white tubes? I have a 27 and a couple 21s that need rebuilding when you're ready.