I work for a company that manufactures solder, so I have a pretty keen eye for it. Even so, it’s still hard to tell a Sn/Pb ingot of bar solder from a Pb-free bar at a glance. The best way to keep these solder alloys separate at your facility is to have a good storage/tracking system and to have them made in different shapes. These pictures depict 2 lots of solder ingot, one is Sn/Pb and the other is Pb Free. Notice the physical difference of the two. This is a fail-safe, in case the ingots are misplaced or left untracked at your facility. Of course, this isn’t anything revolutionary – but perhaps an way to easily add an extra measure of safety into your wave solder process.