A TB'r recommended soaking strings overnight in denatured alcohol, which can be found at hardware stores (search TB for all the recommended steps). That has worked much better for me than boiling them. The strings get new life and I have never detected any damage to the strings as a result. But eventually, you must change them.
Note - I haven't tried this method on coated strings (e.g., Elixirs) and don't know if that would or would not damage the coating or the strings.
Note - I haven't tried this method on coated strings (e.g., Elixirs) and don't know if that would or would not damage the coating or the strings.

