Interesting factoid: To identify if a stick of lead solder has tin in it, hold it up to your ear and bend it. If it makes noise (called "tin cry") it has tin in it. My dad taught that to me at his plumbing shop when I was a kid.
Tin in lead makes it flow better. A 70/30 lead/tin alloy is typical solder (but no longer legal for soldering water pipes).
That IS an interesting factoid!
