We had a VT14 at the RICM that had cataracts. We used dental picks to remove the silicone holding the metal mounting band to the CRT. We planned on using a hot wire to cut the PVA, but when we started picking at the edges of the PVA we found that very little PVA was adhered to both the CRT and the shield. Cleaning up the PVA was tedious, but not difficult.
We were concerned about putting a CRT without the PVA in a public place in the museum. We had images of a young visitor breaking the CRT and glass flying everywhere.
We bought some 0.093" thick Lexan at Home Depot, waited for my wife to go shopping, and put the Lexan on top of the glass shield in the oven. When the temperature hit 325F the Lexan conformed to the glass shield. We trimmed the Lexan to the same size as the glass shield, and use silicone to hold everything together. This is probably a lot safer than the original PVA and won't degrade.
There are pictures and a description of what we did here: http://www.ricomputermuseum.org/Home/equipment/dec-pdp-12/ dec-pdp-12-restoration
I love that you clearly pointed out the most important step in this repair --- waited for my wife to go shopping --- :-) Earl