What is blister copper?

Blister copper is an intermediate product in the process of copper smelting and refining. It is a crude form of copper that is produced by smelting sulfide copper ores in a reverberatory furnace. The molten copper forms blisters on the surface as sulfur dioxide gas escapes, hence the name blister copper.

The process begins with the crushing and grinding of copper ore into a fine powder. The powdered ore is then mixed with flux, which is a substance that helps to remove impurities from the ore, and charged into the reverberatory furnace. The furnace is heated to a high temperature, causing the ore to melt and the impurities to rise to the surface. The molten copper is then tapped from the furnace and cast into molds, producing blister copper.

Blister copper typically contains between 98% and 99% copper, along with impurities such as sulfur, iron, and oxygen. It is further refined through a process called fire refining to remove these impurities and produce high-purity electrolytic copper.