Charcoal Iron refers to the smelting process.

Large tracts of forest were destroyed to provide charcoal to smelt the ore into iron. As time went on other sources of fuel were sought out. The logical replacement was coal. However, the final solution was a coal derivative, coke. So, most smelters turned to coke. The Belgian damascus makers complained bitterly about coke smelted iron. They prized the charcoal produced iron above all other.

It turns out that coke introduces silicon impurities and a certain amount of sulfur, which makes damascus production difficult.

Pete