i believe it was put on the front of the crt to prevent small pieces glass from flying outside the tv set only , i have a zenith roundie with oil between the crt face and the safety glass ,no pva material .

'Nuff said.

I recall your mentioning that before but didn't remember the name of the stuff, must make a note of it.

I think its important to distinguish between roundie color and rectangle. Since this is being discussed on the early I will assume roundie. I would highly recommend care when dealing with rectangle sets that had bonded faces. I have had one go off in the process of removal of a cat and it was something you will not forget, BIG chucks of broken glass flying everywhere covering 20ft or more. I would think that for those you should leave them be (if its just a slight green halo zenith) or maybe try banding, but not sure about how that would work. I suspect the rectangles were never designed to have NO protection at all.

Are you sure the whole thing is filled with oil? Have you ever tried to drain all of it, and is there a cataract forming? I've seen some normal tubes that were developing a cataract where the outer edge of the PVA was breaking down into an oily substance. I think you're mistaking this oily broken down PVA for an oil filling.

But is that glue feasible to remove for a future re-cataract removal? If that glue ever discolors or becomes hazy there needs to be a practical way to separate it without harming either piece of glass that it bonds.

One other argument for the caulk edge method: if the tube you did ever becomes weak or defective you may want to re-remove the safety glass and transfer it to a better tube with bad or missing glass....I have had this happen to me twice.

I've done 2 tubes that were dead before cataract fix and died a while after respectively...Their subsequent replacements had the safety glass ruined or missing, removing the glass from the de-cataracted duds by cutting the caulk was a convenient source of quality safety glass.

In the era when FBP & FJP were both being sold, the bonded tubes used frosted faceplates rather than clear (at least, every one I've seen did). I believe the PVA could help the optics in that case as just having the faceplate a hair too far away from the crt can result in a big loss of focus.

I've read an article in one of the TV repair trade magazines c.1959 talking about Sylvania introducing the first bonded tubes (b/w). I don't recall it mentioning safety, just how it freed up TV designers vs. separate glass. Personally, I do the edges either with double-sided tape or silicone & will continue to do so.

I suspect the original material had a very low viscosity when it was poured/pumped in. Maybe it was heated? Were it as thin as water or mineral oil perhaps air bubbles wouldn't be an issue. I'm not sure how they do it with modern auto glass.

Meanwhile, the vent windows on my '51 Ford have "cataracts" of their own. Rather than replace them I'm tempted to try taking them apart and then re-laminating them with silicone.

electronic m , no its definite oil what kind not sure , but doug has a rca metal table top with oil in the face plate to, he posted it on youtube a few years back, they have a o-ring around it that dries out and they begin to leak everywhere trust me , mine was leaking from day one , on carpet , basement floor , and so on. it's the 21fbp22 doug did his garage i think in that video , he points out how nice and easy they are to redo . rca 1964 ctc-16 drh4683 ,part 2 ,of his video you see the oil before he reinstalls the face plate .

I think on the 21fbp22 equipped sets, that the rubber face plate gasket breaks down and excretes an oily substance. Some folks have mistaken residue for a cataract forming. My Zenith 21fbp22 equipped set has just the slightest oily film forming around the outer edges. I can't imagine one of those rubber gaskets could contain all the oil if the entire face gap was filled. :scratch2:

The "oil" is likely a plasticizer leaching out of the resin.

This has been quite a discussion on this subject, so I'd figure I would chime in. It's always been my understanding the PVA bonded safety glass on the 21fj and others was used to protect the tube from external objects striking the face plate that could result in an implosion. Not the other way around. The 21fj without the safety glass is just as structurally sound as the 21fb, so it shouldn't matter how anyone chooses to re attach the safety glass. Think about it, there's no way these tubes had the safety glass bonded to them during the evacuation process ( I assume pumped down to the 7th scale) and exhaust process. The PVA bonding could not have handled that kind of heat for the time required. I also find it interesting that some of these guys claim the bonding or coupling agent is some form of optical oil on some of these tubes. That could very well be as that was the case on CRT based projection TVs between the tube face and magnifier lense.

There is definitely oil in front of some projection CRTs to keep the tubes cool. My son and I took a projection TV apart for the heck of it. I have even seen kits offered for sale which contain cleaning supplies and fresh oil as the oil gets cloudy after a few years of use.

Oh, the memories! The first TV I trashpicked and repaired (a circa 1959 blond Zenith 16C21 I found in the summer of 1980, I was sixteen) had a weak 1B3 (I was beaming with pride to have recognized the blooming failure and knowing how to fix it immediately!), only to find the picture had a deep brown cast. I removed the safety glass, and used an hour, a whole roll of paper towels, and a lot of window cleaner to get it all done.

Had a lot of fun with that set. It was extraordinarily sensitive on lowband VHF, and made great use of it to chase TV DX by Sporadic-E skip over the next three summers (longest catch: KREM Spokane, 1702 miles from Detroit's East Side).

During the third summer, the abused tuner was getting glitchy. I cleaned the tuner contacts, but when I fired it back up, the performance was only ordinary (sigh).

My guess is that the dirty tuner had been allowing some regeneration to occur, reducing bandwidth and increasing gain.

After several people said they cracked/broke the glass on 21FJP22s while trying cataract removals, I would not have thought the piece of glass (the anti-glare "lens") was "safety glass" at all, in the sense that it might resist breaking or would break into small bits as car windshields do. Am I misunderstanding what "safety glass" is/does?

Also, on the TV sets that had 21FBP22s as opposed to 21FJP22s, I always think of the separate, flat piece of glass that was common on many sets over the years, but it seems that some 'FBP' sets had a separate piece of glass that was basically conical and shaped to fit right in front of the CRT itself; were those pieces a more-"safe" type of glass than the anti-glare pieces that come off 21FJP22s?

I believe the real reason behind the PVA bonded safety glass might be to minimize reflections between interfaces.

Consider light emanating from a source outside of the set and falling on the screen:
In a set with a 15GP22, you have the interface between the air and the safety glass, an interface between the safety glass and the air behind the safety glass, and interface between the air behind the safety glass and the front of the tube, an interface between the front of the tube and the vacuum of the tube, and finally between the vacuum of the tube and the phosphor dot plate. There are going to be reflections at any interface where the light passes from a low index to a high index material. This is basic optics. In the case of light that makes it to the dot plate, there are now a bunch of low-to-high interfaces on the path back out of the set.

All this reflecting has the effect of washing out the picture and reducing the apparent contrast.

The later 15HP22, 19VP22, 21AXP22, 21CYP22, 21FBP22, etc, eliminated the interface between the vacuum of the tube and the dot plate by depositing the phosphor directly on the glass that makes up the front of the tube.

Now consider that the refractive index of PVA (1.48) is much closer to that of the various glasses (1.40 to 1.60 for most varieties) than it is to air. You would be replacing a air-to-glass interfaces with PVA-to-glass, and since the indices of refraction are much, much closer, you would minimize the reflections to some degree. Granted, there would still be reflections at the interface between the PVA-to-glass interfaces. Even glass-to-glass interfaces (with two seperate pieces in direct contact) must exhibit some reflecting as the structure of the glass itself is not continuous and there are gaps and voids between them, etc. Still, the severity of the resulting reflections is substantially lower.

The PVA bonded tubes should give less "glare" from ambient light than a 21FBP22 set. I can say that there is much less glare on my CTC-7 than the Westinghouse H840CK15, and I suspect that a CTC-16 with its bonded tube would exhibit less "glare" than say a CTC-7.

Here's the video showing the oil https://www.youtube.com/watch?v=VlWXNVJ5fN0

Maybe not THE reason, but definitely a benefit. In medicine, the saying would be "There are no side effects, there are only effects."