The grant we're talking about here is a critical piece of our brewhouse. If you've ever been on a brewery tour or brewed beer at home, you already know that virtually all breweries have at least two stainless steel or copper vessels in their brewhouses. You can't really get by without having a mash-lauter tun (MLT) and a boil kettle (BK), though there are exceptions--just check out Lunar Brewing Co. in Villa Park. A good chunk of breweries also have a hot liquor tank (HLT), though Pipeworks manages just fine with instant in-line water heaters. We've already covered the heat exchanger, which is the last stop for wort in our brewhouse before going into a fermenter. That leaves the grant.
When it happens, you can hear and feel the brewhouse shake. Your colleagues give you the "Who hired this asshole?" look that makes you shudder in your sleep.The purpose of the mash-lauter tun is twofold: 1) to rest a mixture of grain and water--"the mash"--in a specified ratio for a specified time at a specified temperature, and 2) to separate the solid and liquid portions of the mash, discarding the former and sending the latter--at this point called wort--to the boil kettle. During that second step we use an impeller pump to transfer wort to the kettle. The thing about impeller pumps is that they need liquid. Seems obvious, but consider the fact that for wort to get to the pump, it has to pass through a two-feet-thick bed of wet grain. Lautering is prone to flow rate changes and stuck mashes due to gelatinizing proteins, density and temperature differentials, chasing first runnings with sparge water, and so on. On a good day at Solemn Oath, lautering is something like a pharmaceutical commercial aimed at the 50+ male demographic: a ninety-minute breeze with steady flow. But when we use gummy adjunct grains like wheat or oats, brew a really big beer, or miss our mash density target, that time can double and really get in the way of our Dancing With The Stars habit. When it hits four hours--it only has once--forget calling a doctor; it's time to crawl in an empty brite tank and cry.
On a good day at Solemn Oath, lautering is something like a pharmaceutical commercial aimed at the 50+ male demographic: a ninety-minute breeze with steady flow.So if we were pumping directly from the mash-lauter tun to the boil kettle, given the flow-rate variability endemic to lautering, we wouldn't always have a steady flow, which would give our pump a hell of time. You see, if liquid isn't flowing into the pump as fast as it's being pushed out, we create really gnarly low-pressure pockets and pull air. At that point, those air bubbles collapse against the face of the pump, sending hot liquid jets of wort hurtling at one of our most critical pieces of equipment. This is called cavitation. When it happens, you can hear and feel the brewhouse shake. Your colleagues give you the "Who hired this asshole?" look that makes you shudder in your sleep. It's no good. To combat this problem, we have a grant. It's a reservoir that collects the runoff from the mash, allowing us to maintain a liquid buffer ahead of our pump as well as pull samples whenever we want for whatever we please. Sometimes this includes face-painting and coffee-flavoring, but mostly we take gravity and pH measurements. Translated to all-grain homebrewing, the grant is the equivalent of the saucepan you use during vorlauf to collect wort and pour back over the mash or into the kettle.
I hereby grant you a more nuanced understanding of commercial brewhouses and the importance of flow rates, sampling, and pumps! Pumps! See what I did there?
This is the fifth post in my “What’s That Thing Over There?” series in which I reveal the extraordinary and mundane of brewery miscellania. In my previous posts, we talked about how beer is like sausage and legislation, got the skinny on the troll that lives under the brewdeck, proved how reading CO2 levels can make or break you, and explained why chemical burns are no fucking joke. Next time, who knows? The Thing you’re wondering about may be on deck. Just please, stop asking our poor bartenders what that damn thing over there is.