The liquid wort (as it is now called) contained in the mash tun is strained off through the perforated false bottom and pumped into the copper. This takes about an hour during which time the remaining sugars are rinsed out by spraying the mash with hot liquor, a process known as sparging.
When sparging is complete, the remaining ‘spent grains’ are removed from the mash tun and put into sacks (strangely, there’s not much competition among brewery staff to perform this task). The sacks of spent malt are then taken away by a local farmer for animal feed.
As soon as the wort covers the stainless steel heating coil in the bottom of the copper, the gas-fired heater is switched on and starts to heat the wort. It reaches a vigorous ‘rolling’ boil some two hours later.