Variation in the melting point of metal alloys between an ingot and a powder...why? I have Bi58Sn42 alloy in ingot and powder form.  The listed melting point is around 135 - 140 C.  When stick the ingot in an oven at 140 C it melts just like it's suppose to.  However, when I stick the powder in the oven, it doesn't melt.  I heat the powder all the way to 200 C and it still doesn't melt. What gives? Why isn't the powder melting but the ingot does? 