I wonder how "wet" rosin stays after a year, 5, 10...
I recall seeing some solder, with some sort of flux, that was dry and crumbly, and fell out of the end of a cut piece of solder.
My newest solder is 25 years old, this year, sits in a garage that ranges from ~35 degrees in the winter to about 105 in the summer, no issues as of a couple weeks ago.
When heated, the rosin would flow out, and whet the joint nicely, and flow and dance around it, followed by the solder, leaving a flawless, shiny joint. After cooling, the rosin was slightly tacky, and I used alcohol to clean it off.
In the 70's or so, Dad had acquired several large rolls, each about the size of a small coffee can, that had a stearin core. That stuff was dry throughout the roll, but no problem with usage, it quickly melted when hot.
I've always had excellent results with rosin core, whether new, or old. Acid core, used once, it worked, but old solder doesn't seem to survive, stearin core, no issues for the application, non flux cored (60/40, I think), I use my own home-made flux for electronics, and on other metal pieces, Nokorode (newest about 40 years old now).
Seems a lot of the issues arise with unknown, oddball, filthy solder.
Kurt
