First off some background for those not familiar with CRT cataracts:

When the transparent glue (PVA) that bonds the safety glass to the screen of many 60's -70's CRTs fails it takes on a color and or haze around the edge (which works its way in as the failure progresses). The color of the discoloration being the way most identify the two types we categorize cataracts into.

Most people identify cataracts as either:
RCA type which has a hazzy white often moldy looking discoloration that is nearly impossible to see detail through.
Or
Zenith which is typically a transparent green that is close to being yellow.

The two companies were the biggest makers in the era that tubes had glued safety glass, but were far from the only OEMs to produce such tubes. Due to shortages and after market replacements I've seen both types of cataracts in the other makes set and some of the smaller makers used whatever they could source in a given week.

RCA tubes the glue tends to be like a hard semi flexible plastic(but not always). The most effective conventional ways I've seen are the sun method (remove some edge PVA insert wedges set in hot summer sun face up and as the edge delamination moves in push wedges farther in to keep it moving), the heat gun method (warm CRT screen in sun or heat lamp then heat screen with heat gun to delaminate with heat working inward, wedging from sun method optional), soak method (place tube face down in large container of water possibly containing ethylene glycol covering the highest edges of the PVA let stand a few months till the safety glass comes off by itself), hammer and chisel (because life didn't suck hard enough:thumbsdn: ).

Zenith cataracts tend to be a thin goo on the outside and somewhere between warm mozzarella and day dried springy bathroom silicone caulk on the inside. The best ways to fix it I've seen are the wire cutting method (attached single strand 18 or thicker guitar string solidly to 2 end handles and pull the wire through the glue to cut it alternating which handle your pulling on once resistance becomes substantial, some folks run current through the wire to heat it), the heat gun method used on RCA tubes, and the hammer and chisel method (how it comes to that I can't fathom but doing this is it's own punishment so I won't add insult to injury)....I think someone tried the RCA water method on a Zenith CRT but I don't recall reports of success, nor would I expect success so I will only mention it.

Any method involving heat or chisel risks implosion uneven temp changes and or mechanical impact are the enemy of glass (some have hurt themselves and sworn off it), I personally can't get the wedging to work without destroying the safety glass[it is a VERY fine between not enough to make delamination ever happen and cracking the safety glass] and finishing the job with a chisel, and am am fairly leery towards using a heat gun since it seems the most dangerous). Water I've only seen work for others and on tubes left in unclimate controlled intermittently flodded basements for decades. I tried leaving a RCA tube submerged for a whole summer and it did not increase the delamination at all for me so I have given up on the safe water method.

Once the safety glass is off clean the PVA off and if the safety glass is intact add some spacers and tape or caulk the glass back onto the CRT along the outer edge. (I prefer the caulk method because it guarantees no dust or dirt can get in long term.)

It should be noted CRT rebuilders of the day used sepcial ovens to melt the glue... most CRTs are too big to safety do in anything but a custom made for the job oven.

The best way to do a Zenith cataract and my favorite method overall for either type is the cutting wire method...It is fast, not particularly difficult assuming average adult male arm strength, and and very safe (I've never damaged a CRT safety glass, or hurt myself using it) and results have been consistently good.
Earlier this year a well known Chicago collector (who I'll let chose whether to identify himself) who does cataract removal, asked me if the cutting wire method could be used on both Zenith and RCA tubes. I told him I hadn't tried it on RCA types a did not evpext it to work. However in his inaccurate speculation of how I did the process he had some clever ideas that got me wondering if it was possible. On Sunday I tried it and learned something new I feel like I should share...

First off PVA varied a LOT from maker to maker and over time. Most Zenith tubes the PVA just peels off the glass easily by hand once the safety glass is removed from the CRT, but at least one I've done it had a center patch that was on there like curred bathroom silicone and I had to scrape and use chemicals to remove it. RCA style cataracts vary quite a bit too ...I normally think of them as a hard semi flexible plastic that is brittle where discolored, but I have seen some that are hard as rock and some that if warmed up are soft and springy in the middle with a consistentcy just slightly less soft than a Zenith CRTs PVA....I successfully used the wire method on an original Philco 22JP22 with an RCA style cataract. The tube had the moldy white cataract, and the discolored outer PVA had the same consistency as RCA PVA normally does but the inside was fairly soft and springy and it worked well once I got through the outer layer.
After that I tried it on a genuine RCA 19GWP22 and the wire did nothing... the genuine RCA had PVA that was as hard as plastic all the way through. It might have done better if it was heater more by the sun or if I had heated the wire.

This may be worth trying on some RCA style cataracts in the future.

I've only dealt with two CRTs so far; a Zenith 25GP22 and the weird wide CRT in a Datapoint 2200. The Zenith was the typical green halo and was the first one I did. I tried a heated copper wire but had little luck with it so I went out and got a heat gun. With the CRT wrapped in a heavy blanket I heated the faceplate as evenly as I could until small "fingers" appeared near the edges. Then I gently pried away the safety glass while still waving the heat gun around the faceplate. The PVA material was pretty easy to remove at that point. The Datapoint CRT was more like the RCA type cataract, but being a pretty small tube the heat gun worked here as well. Guess I was lucky both times since nothing went wrong.

At the time I thought about using a Nichrome wire, but didn't know where to find some.

The only one I ever did (ever will do ) was my RCA 21FJP22A, and followed shango066's method shown in his video exactly, sun for 2 hours, then heat gun, and it popped right off, and the gunk easily came off in one piece by hand, leaving only slight a white ring around the edges. :o

I've only dealt with two CRTs so far; a Zenith 25GP22 and the weird wide CRT in a Datapoint 2200. The Zenith was the typical green halo and was the first one I did. I tried a heated copper wire but had little luck with it so I went out and got a heat gun. With the CRT wrapped in a heavy blanket I heated the faceplate as evenly as I could until small "fingers" appeared near the edges. Then I gently pried away the safety glass while still waving the heat gun around the faceplate. The PVA material was pretty easy to remove at that point. The Datapoint CRT was more like the RCA type cataract, but being a pretty small tube the heat gun worked here as well. Guess I was lucky both times since nothing went wrong.

At the time I thought about using a Nichrome wire, but didn't know where to find some.

I've tried heating wire...it always softened the wire to the point it would snap far too easily to work. I quickly learned that all Zenith style cataracts will cut with a UNheated steel wire and some elbow grease...the CRT doesn't even need to be warm. I successfully did a Zenith type cataract removal with cold wire on a 45degree fall evening.

I've done 3 or 4 of the RCA type using a heat gun, with no drama. In another case I wanted to save the faceplate from a dud Philco-built tube with the RCA type PVA. At the time I had access to some infrared lights used to dry paint; the same bulbs as a "french fry warmer". I aimed these at the face for perhaps 30 minutes and the plate popped off nicely...but the aired-down crt developed a large crack.

On another aired-down tube, where I wanted to save the plate, I used a propane torch and that worked very well. I believe I'd be daring enough to try it on a "live" tube. It seemed very similar to the heat gun (I no longer have one of those).

I learned the water method years ago by accident after pulling a 21FJP22 out of the woods (where I'd left it years earlier, unaware that it could ever be of any use with a serious cataract). The only thing holding the faceplate on was what remained of the tape. Based on that I was able to do one RCA after soaking and using wedges for a couple weeks. (I've found I don't really need wedges with heat.) I have tried a Zenith and a Zenith-type from a Motorola (I forget who made that tube) and neither was successful. In both cases I cracked the plate in trying to remove it.

If there is a next time with an RCA, I think I'll start with the sun. For a Zenith I'd look for some of the wire used to cut out windshields.

Has anyone dealt with ~12" Clinton CRTs where the mounting band is like a dish that the CRT and lens is epoxied into? I attached some pictures of one. I couldn't figure out how to get the lens off without destroying the mounting band. I thought about trying to break the safety lens and not disturb the crt or band.

-J

I don't see a cataract on that CRT. I'm I missing something that my old eyes aren't seeing?

Has anyone here tried the soak method for cataract removal on RCA type CRTs?
How long does it really take? The only reference I have is an old youtube video from shango066.

I tried it on an RCA made 25" rectangular. ~2 months in the shed with tap water followed by ~2 more months of etheline glycol and water mix and all it did was rust on the tension band and brackets. I let it stew from spring to the last warm week of summer then switched to the sun method.

There are MUCH older (like 5-10 year old) threads here where people have had success with the soak method. It seemed like it was on roundy CRTs with advanced cataract delamination.
Some of the older threads mis spelled it Cateract.

You can see how badly advanced this is, it is just about as bad as my CTC-16XL was.

It's the wrong time of year to try the sun method, and thus i opted to try soaking this time.

I could try jamming a few spudgers in between while it's soaking to give it a little nudge.

You can see how badly advanced this is, it is just about as bad as my CTC-16XL was.

It's the wrong time of year to try the sun method, and thus i opted to try soaking this time.

I could try jamming a few spudgers in between while it's soaking to give it a little nudge.

If the highs are in the upper 70s, there is strong direct sunlight, and you put a black trash bag over the screen to concentrate heat it probably will work....Warm summer days in Wisconsin translate to average late fall days in the south.

I know people here who will complain they need the AC on if it gets above the mid 60s...

I've tried heating wire...it always softened the wire to the point it would snap far too easily to work. I quickly learned that all Zenith style cataracts will cut with a UNheated steel wire and some elbow grease...the CRT doesn't even need to be warm. I successfully did a Zenith type cataract removal with cold wire on a 45degree fall evening.

When I did the cataract in my Motorola WID, I found that a wound guitar string worked well - kind of like a saw. Better than just a regular wire. I attached it to two pieces of broom handle, and just went for it. What a mess to clean up after I got the glass off though.. not excited to ever do that job again!

When I did the cataract in my Motorola WID, I found that a wound guitar string worked well - kind of like a saw. Better than just a regular wire. I attached it to two pieces of broom handle, and just went for it. What a mess to clean up after I got the glass off though.. not excited to ever do that job again!

It's only tedious till you end up chiseling off an an RCA safety glass and get skewered all over by glass chips...compared to that hell the work of dealing with the sawing and glue on a Zenith cataract is positively wonderful.
I've done around 10-15 RCA cataracts so far (and a comparable number of Zenith ones) and of the RCA cats I've fixed only 2 did I not end up having to chisel....Both the successful ones had advanced delamination. One fell off when I peeled the tape the other had a 6" diameter attachment point that was cooperative....I might need to do this in hotter weather and use a heat gun but I'm not super comfortable with that...