A better "trick" than boiling is to clean the strings with amonia. Just loosen the strings enough to be able to lift them away from the fingerboard, dab a clean soft cloth in the amonia and wipe the strings. Loosening the strings allows you to wipe the underside too. You may have to repeat the process a couple of times to get all the crud off and you may want to do this outside, amonia has a pretty strong odor. I got the idea from a jeweler friend who uses amonia to clean rings and things, tried it on an old set of bass strings and discovered it works fairly well, and it is a lot faster and easier than boiling them. Neither method will last very long (maybe 2-3 hours at best) but for a quick fix when you are in a bind, a quick cleaning with amonia will get you a little more playing time on an old set of strings.