Owl Brewing Company - The Brewing Process.
At the very top of the brewing tower our "Cold Liquor Tank" holds up to 1000 litres of fresh cold water, to supply all parts of the brewing cycle from Hot Liquor through to Cask Washing.
Water from the cold liquor tank is used to top up the "Hot Liquor Tank", although much of the Hot Liquor comes from the Heat Exchanger (see later). The Hot Liquor is heated to 70 centigrade by electric heaters before passing down into the "Mash Tun".
The "Malt Hopper introduces Malted Barley along with the Hot Liquor into the Mash Tun and brisk stirring is needed to ensure the crushed and milled malt is fully dispersed into the Hot Liquor. For 90 minutes the "Wort", as the mixture is now known, is regularly stirred so that the hot water mixture can convert the malt starch into fermentable sugars and dissolve the sugars out of the Malt.
After 90 minutes of "Mashing" the wort is allowed to settle so that the residual grains form a filter bed in the bottom of the Mash Tun. As the sweet wart is drained from the bottom of the Mash Tun almost all of the solid liquid matter is filtered out, leaving a clear sweet liquid. A small amount of extra Hot Liquor is gently sprayed onto the grains to rinse out the last of the sugars without disturbing the filter bed.
The clear sweet wort passes down into the "Copper" where the hops are added (for bitterness) along with the conditioning to harden the water. The wort is held at a "rolling boil" for the next 90 minutes to complete the conversion of the sugars.
At the end of the "Coppering" the wort is at 100 centigrade, far too hot for the fermenting yeast to survive, so we must pass it through the "Heat Exchanger" to cool it. The Heat Exchanger takes the temperature down from 100 to 22 centigrade and dumps the excess heat into water which is passed up into the Hot Liquor Tank, for use in the next brew.
At 22 centigrade the Wort is just right for the Yeast and is passed down into a "Fermenting Vessel" where the live Yeast is pitched onto the top of the liquid. Brewers Yeast feeds on the dissolved sugars, reproducing and excreting alcohol as a by-product.
At some times of the year all this feeding and reproducing causes the Yeast to overheat, so we use "Cooling Coils" to hold it down to 22C.
After approximately 4 days the Yeast will have reproduced through 7 generations whilst consuming most of the sugar and excreting enough alcohol to slow its self down. Measuring the specific gravity of the beer (as it now is) tells us whether the desired amount of sugar has been consumed (and the desired amount of alcohol produced).
The Cooling Coils are now turned up to cool the beer to 6 centigrade so that most of the residual Yeast becomes dormant, falling to the bottom of the Fermenting Vessel to form a stable sediment.
Another 2 days at 6 centigrade, the beer has "dropped clear" and is ready for cask filling. To help the beer sparkle a small amount of priming sugar is added to each cask so that the small amount of residual yeast can feed and generate some carbon dioxide gas in the beer - hence the term "cask conditioned".
We operate a traditional 7 day brewing cycle in a classic "Tower" brewery configuration.
Modern microbreweries usually operate all the brewing processes on a single floor, using pumps to transfer the liquids between stages. We are rare amongst modern breweries in using a tower configuration spread over three floors so that our first process is at the top and gravity transfers the liquid from stage to stage until the casks are filled in the cellar.