Originally Posted by
goodsteel
I have a lot of experience with eutectic solder which is the lowest melting temp solder that there is according to bumpo's list up there. Anyway, eutectic solder has the specific characteristic that it has no slushy stage. Its either solid or frozen, but no slushy. It has a problem that when cast into muffin tins, the outside cools and freezes faster than the inside and it will sometimes squirt molten lead out of the top of the ingot and leave a divot in middle. This is the only alloy that does this to my knowledge and although its not a definite test, it would be another clue. It wont do it unless its cooled pretty quickly. The solder pots at my day job only do it when the air vent is left running right over the pot (the air flow cools the 1Lb pot pretty quickly) but I had every one of my muffin pan ingots do this. Hope it helps!