If we heat 100kg coal in the retorts, we have 25 sq.m. of gas. The remaining 75 kg are the coke, which has nothing to do with our favourite drink. It is the coal that has been heated and transformed. After the burning, the coke had to be removed from the retorts, so the workers put it in the courtyard, doused it with water in order to cool it down and therefore re-use it as a fuel for the Gasworks or elsewhere.