I have been using this stuff for eight years now to build mostly high-powered YAG boxes for the government. 93-500 or "thixotropic" as I have come to call it is just about the best stuff due to low outgassing and removability. But today I had an issue where the stuff just wouldn't cure. I tried using it to seal an off the shelf blower (fan) that was supposed to already be airtight. Well, the body of the fan is some sort of plastic and I wonder if the composite has something in it that reacted with the 93-500. Anyone out there know anything about this stuff? The quantity of glue in my syringe cured alright overnight.