Last year, I read a "tip" on the acoustic guitar forum that wool makes a good string cleaner. The author of the thread had a friend who was an analytical chemist and was also a guitar enthusiast. He described how wool evidently contains a chemical that not only cleans but actually helps remove and reduce tarnishing of the bronze wound strings.
Off I went to my local tailors, and obtained a sample piece of 100% wool suit material. I've been using that ever since.
Just thought I'd throw that in!