What is blister copper?

Blister copper is an intermediate product in the copper refining process, typically containing around 98-99% copper. It is produced by smelting copper ores, where the sulfur content causes the formation of bubbles, giving it a blistered appearance. The blister copper undergoes further refining, often through electrolysis, to achieve higher purity levels suitable for industrial use. Its name derives from the blister-like formations on its surface due to trapped gases.