I have been using a Lee melting pot for close to 20 years. Last October my old pot wore out,( heating element died). Since getting my new pot I have had the lead turning colors, blue, red and green, and leaving deposits in my bullets. I use .350 , .490 round ball. the deposits are heaviest in the bigger bullet, which is to be expected.
My Dad, who has been casting for over 50 years, has never seen anything like this either.
I assume that rust has gotten to the inside of the pot. Will this decrease with use?
I use midway 99.9% pure lead and flux with SPG Lube, Although I have used other lubes in the past.
