There are lots of ways you can clean your soldering iron tip, but i never saw one that cleans so well. Have you ever tried cleaning it with one of these ?
soldering hintsoldering-hint-3

I think it’s main use is somewhere in the kitchen, but it works great for cleaning the soldering iron tip. Or if you like the pro version of this cleaning sponge you can take a look at Curious Inventor, I have to admit i first saw the idea there.

and the results…

before cleaning

before cleaning

after cleaning

after cleaning

These things cost about $0.5 from where i got it so it’s cheap investment for a clean tip 🙂