Hello.
I’m MapleEngineer. I’m from Eastern Ontario and I’ve been soldering for over 40 years as a hobbyist. My user name is MapleEngineer because I’m an artisan maple syrup maker and design and build my own machinery and industrial controllers.
I, like just about everyone, started out with a pencil iron and a bit of solder in a clear plastic tube.
If you’re into electronics and soldering please subscribe and feel free to contribute and ask questions.
In this case I believe that it was simply white silicone caulking. I’ve run into potting compounds and epoxies a number of times. There are apparently solvents for most potting compounds but I’ve never used them.