Every winter, my dad would disappear into his workshop where he'd distill day and night solidly for 3 months. It's a 24 hour work day once distilling begins so he'd literally move in, bed and all. This is the first step of turning wine into Cognac and that huge copper contraption was his potstill, or alambique as it's called in French. You put the new wine in, distill it once, distill it twice and a day later out comes the eau de vie (literally - "water of life") that you then mix with water and age to make Cognac. The potstill is precious and ours is ancient. My dad's gone now but she's still going strong. She's been in the family for generations.