Sullage is the non-metallic waste that rises to the surface of molten metal after it is tapped from the furnace. It consists of oxidized alloys, refractory dust, and flux residues. Foundry workers must skim this crust off or use a bottom-pour ladle to prevent the dross from entering the mold and creating weak spots in the final casting.
Heard on the job
Skim that sullage off the top before you pour, or we'll end up with inclusions in the cylinder head.