How to fix loose CRT base - CTC11-12's

[DavGoodlin]

Ive got three tubes with different issues but all have a loose base. The '72 RCA colorama 21FJP22 that had its base skirt busted off goes first. Ill start by carefully extracting the solder from the pins of a donor base off a dead Sylvania 21FK and then double extra careful removing the busted-in-half base on the tube under restoration. I do not feel like re-soldering a lead busted off at the glass

Now what do I do? It needs to be non conductive, heat-resistant yet bond glass and phenolic. I saw a thread about a recipie for the crunchy caramel-colored glue-filler somewhere