Converting consists of eliminating any remaining sulphur and iron from the copper matte. The end result is almost pure copper.

The matte is run into a converter, a large cylindrical furnace that rocks back and forth and has an opening at the top.

		Converter used to purify the copper matte.
	Source

First the copper matte is poured in through the opening at the top. Then oxygen-enriched air is blown into the matte. This maintains the temperature at around 1,300 °C.

The remaining iron binds with the oxygen and floats on top of the matte and is removed periodically.

Once the iron has been burned off, the oxygen from the forced air binds with the sulphur to form a gas, which is captured. The entire process takes about four hours.

In the end, the copper is almost entirely free of impurities: it is 99% pure and the only substance remaining in the converter. It is called "blister copper."

		Converter used to purify the copper matte. Note the size of the man, on the bottom left.
	Source