another cat removal
 

this time with water. a 21FJP22. I picked up a small kidde pool (baby really) at target for 5$ fits just right. I don't have my camera handy but will snap a pic later. I used a exacto to cut the tape seam righ at the lens, then peeled it off. the pva as not as hard as I have on some other sets, more like cheddar cheese, maybe ti will go a bit faster than the last one I did (a RCA rectangle, the PVA was much harder on that one. I did that one with the low temp low pressure method. Hopefully the somewhat softer pva will let the water soak in and do its thing in not too many days.

I have the water just above the glue line. I can see that I will have to keep an eye on it for evaporation losses. there is also a bath cloth under the lens, I dont think its needed since the plastic liner bottom shoule be enough to protect it from scratching. I have it on a concrete covered porch.

here it is

give it awhile and it will pull right off.i think this is a much safer way than the heat method.good luck

yea after that report of the failure, I decided to hold off until a better method was tried. I like this one the most.

I was going to to the low heat (out in the sun and low pressure from chop sticks) like I did on the last one, but honestly I was concerned about some dopey kid chucking a rock from the back yard (it happens) an then I would end up in jail... so this seems the best and def the safest for the tube.

it took mine 2 months to fall off, i would try and get it a spot in the garage. There is no way I would let it sit outside that long.

The clear silicone worked out very well. The thing is super strong and sealed for life.

being a man of "science" I plan to add some yeast to it later. hmmm I wonder if a CRT weighs the same as a witch...

Update:

been about 10 days, I lifted it up and applied some pressure (finger nail under the lens) I could see some sign of release at the very edge, the pva was coming loose from the CRT face. Just a tiny bit mind you, but progress none the less....

I'm anxiously watching your progress. I've got two round color crt's that are in need of safety glass removal and I decided a long time ago I was not going to risk the destruction of the tubes (or myself) by using localized heat to pry off the mask. I've got my kiddie pool all ready to go and am waiting for the weather to finally warm up a little bit here in the North East.
Bob

If the PVA is indeed polyvinyl alcohol "PVA", then water solubility is really the only way to go. It essentially turns gummy after a while. If you can get some water circulation going it would certainly speed up the process. (a small aquarium pump directed at the PVA might help).

I used the same method on an oddball 15' rectangular(thick neck) crt from a conrac monitor,took awhile,but it worked.
Pat

agitation, I will see what I can do on that, will look for a small cheap pump.

I was also thinking of some tooth picks stratigically placed around the edges too apply a tiny bit of pressure, and open up the pva to more water.

The water does not dissolve the PVA in any way. It just somehow causes it to unstick to the glass.
The PVA sheet from the one I removed was in good shape. It didnt dissolve at all.

It's actually of the family of Polyvinyl Acetates - kinda like fancy elmers or wood glue.


Later they used polyepoxides - no cutting through that stuff! Patent 3,265,234 from Union Carbide spelled the death of PVA resins, I imagine.

Cheers,

I may keep the mounting hardware on mine to keep it elevated up a bit. Then I can watch for the glass to fall off! :D

Polyvinyl acetate is soluble in VOCs... I wonder if acetone might help then. (or ether if you can get it, but it's a little less "safe" to work with.)

I've tried several things: acetone, methyl alcohol, grain alcohol, stripper, spirits....

Nothing touches it, nothing. I always resort to chipping the lens off with a screwdriver, since I use tubes in sets with flat glass anyway.

In light of that I'd suspect there are numerous additives they put in it to get it to bond to the glass; those additives must be what solublizes in the water and also keeps things from easily eating away at the PVA.

I can def see the little stress fingers around the edges where the toothpics are. Just have to be careful handling it with all the water making for slippery handling...

I wonder if there are any chemists on VK or ARF that would be willing to research the possibility of designing a coumpound to disolve PVA in a comparable amount of time to the risky heat method?

Tom C.

Trouble is anything that's going to work well is also going to be very nasty, and leaving something like that open is a no-no.

Agreed. I'd further suspect that trying to dissolve the PVA will leave you with a nice gummy mess on your tube and safety glass... If we can find out the bonding agent that is affected by the water, it may be possible to do better. I wonder if it would make a difference to gently heat the water to say, 40/50 degrees C. Not too stressful for the tube, and if done slowly, it allows a thermal gradient to establish with minimal stress.

Zenith comes close with their patent for reducing thermal gradients during CRT "salvage"

How about Acetic acid for a solvent? PVA glue (Titebond wood glue) reacts to the stuff....someone with salvaged PVA could possibly test the theory.


Cheers,

Seems like if you used a solvent it would result in a gooey toxic mess to clean up. Thats how the Zenith green halo ones are, its like jello that smells like a combination of sewage and used crankcase oil.
I avoid the Zenith ones now because cleanup is so time consuming. Yea you can cut the window off in 20 seconds with a piano wire, but then spend a week trying to get that goo off.

I have a piece of pva, ill try some solvents when I get time but still think I would prefer water.

So, stick the tube in a vat of vinegar?

If it was pure PVA, then vinegar might work... see here:
http://www.ehow.com/how_5650421_dissolve-wood-glue.html

Worth a shot, I guess.

Edit: Glacial acetic acid would be more potent... but harder to get a hold of. You could probably make some by distilling or concentrating vinegar, depending on the acetic acid boiling point.

dumped in 1/2 gal of vinegar...

DO NOT dump glacial acetic acid into a pool like that (if you happen across some). If the smell doesn't blow you away (it can damage the lungs) it will likely dissolve the pool. A half gallon of vinegar probably won't do much of anything, but hey, it can't hurt, and it's cheap enough.

I remember seeing a posting with pictures of this kiddie pool submersion method, and they stuck popsicle sticks into the edges of the pva as it worked loose. It did a great deal to speed up the process.

You can make a little tent with a blue tarp or taped-together garbage bags. Could help with smells, too.

Phil Nelson

I recently learned, to my surprise, that glacial acetic acid is flammable.

The article on reducing stress is very interesting, but it deals with faceplate removal from the bell by melting the frit which involves much higher temperatures.

I suspect that the problem with the heat method isn't thermal stress, but that the PVA or other material has plasticizers in it. With PVA it's probably water. When you heat it the plasticizer becomes a gas and when trapped makes a high pressure between the cover glass and the face of the tube.

I seem to remember in an earlier cataract removal thread someone saying that bubbles would form as they used the heatgun.

John

well something is getting nasty, the water is def getting murky looking, and I am seeing life forming in the way of little larve looking nasties, yuk...

See if they eat the PVA. hahaha

That's an idea, put the beasties to work!

They might be mosquito larvae-it's the right time of year for them to start coming out. Whatever they are, they are pretty tough to tolerate all that vinegar. Maybe throw one of those mosquito poison cakes into the mix-you don't want to see how many can breed out of that pool.

... and watch the safety glass fall right off the instant the poison hits the water :D

Seriously, be careful doing that, you don't know how it would react with the vineagar.

I just pluck them out and let them dry up. I think I have a toxic enough soup as is. its starting to look like the bottom a hookah pipe.

Don't drink the bong water.

Put a bottle of cheep vodka or a cup of gasoline in there. Lets get this party going

maybe can find some mad dog 20/20 to pour in.

:puke:

today I poked around it some more, the PVA seems a bit more pliable now. It was rock hard when this began, but somewhat rubbery feel now on the bits I pulled up around where I had jammed in the wook sticks.