Gearhead: Monster Mashes & Tuns of Fun

As brewers pursue ever higher gravities for richer, stronger, thicker stouts, something immediately becomes clear: Most breweries weren’t made for this. Here’s a closer look at how breweries are adjusting for huge grists, long boils, and viscous beers.

John M. Verive Feb 10, 2021 - 14 min read

Gearhead: Monster Mashes & Tuns of Fun Primary Image

Cycle’s mash tun is roughly three times the size of the kettle next to it.

“Stouts are never going to be easy,” says Cory King of Side Project Brewing in St. Louis, often lauded as a master of the sort of modern, high-gravity concoctions that feature big alcohol levels and even bigger volumes of flavor. “Making a beer that big doesn’t make sense on paper.”

Whatever you call them—often pastry or dessert stouts—these new-school takes on imperial stout are all about pushing the limits, and a robust fan base has emerged that’s every bit as obsessed as the hopheads and haze bros. Brewing this super-charged style is a balancing act like any other, but the stakes are higher than with most other styles. The margin for error is slimmer, and with costly ingredients and long production times, it can feel like a high-wire act without a net. Many of the brewers making the paragon examples of the modern imperial stout started on brewhouses that were by no means optimized for such extremes of wort production—as target gravities creep ever closer to 40° Plato (SG 1.179).

However, there are a few different approaches to brewhouse improvements that can make those huge beers easier to brew, from maxing out the mash tun to more focused capital improvements. Like everything else in the brewery game, the proof of what works best is in the pudding (stout).


A stout mash in progress, inside Side Project’s oversized mash tun.

Supersizing It

“You can’t design a system for both extremes,” says veteran brewery engineer Tim Heath. You can set up a brewhouse to be efficient and capable of making a large range of different styles, he says, or you can design a specialized system that’s great at something specific.


The first way was once the standard buildout for American craft breweries: moderately sized, two-vessel brewhouses optimized for the pale and amber beers that were de rigueur during the brewpub heyday of the 1990s. While capable and flexible, these setups are like brewing “with one hand tied behind your back,” Heath says, because of the reliance on a single vessel for mashing and lautering. He suggests a separate mash mixer and lauter tun for any new brewery that has the extra space. It isn’t just about the time it takes to go from mash-in to wort in the kettle, but also about the quantity of sugars you can extract from the grain and the quality of the resulting wort. But the three- or four-vessel brewhouse is by no means a prerequisite for brewing even the biggest, densest, modern imperial stout.

At Side Project, their two-vessel setup has something in common with many other big-stout brewers: an oversized mash tun to handle large grain bills. “We built a mash tun to do this; I did the calculations myself,” King says of the upgraded brewhouse, which can handle 3,000 pounds of grain for barrel-aged stouts, or it can comfortably brew 6°P (SG 1.024) table beers.

The core of the upgraded system is a 30-barrel combo mash-and-lauter tun paired to a 20-barrel kettle. There are some custom upgrades to the oversized tun: a higher crossbar that allows for deeper grain beds, bigger rakes to cut through the thick mash, and a bigger motor to run the rakes and plow. It takes four or five hours to lauter the “theoretical 20 barrels” of wort. (“Some days you get 18 barrels out, and some days you get 12,” King says.) The boil begins when the first runnings hit the kettle and continues for three more hours after the lauter is done. The brewers turn the brewhouse like this twice in two days to fill their primary fermentation vessels. After the Chico strain has done its work, the beer is racked into spirits barrels and stacked for a year to 18 months before being blended into a final release. King says he has a sweet tooth himself, and his expertise at barrel-aging and blending helps Side Project’s big stouts earn their reputation as some of the best of the genre.

Cycle Brewing in St. Petersburg, Florida, is another one that’s built a name on big stouts and special releases. When it was time to expand to a facility focused on barrel-aged beer, Founder and Brewer Doug Dozark also chose an oversized mash tun with high-gravity brewing in mind.


He specced a 15-barrel brewhouse for the new facility but knew he’d need a tun that could handle a ton (or two). “I don’t know where the standards for sizing tuns and kettles came from,” Dozark says. Instead of the standard calculation, he sized his mash tun by measuring the physical space he had available, then had the brew deck fabricated to hold the largest tun that would fit. It can hold about 46 barrels. “I’d go bigger if I could,” he says. The cost for the upgraded tun was negligible; the biggest challenge was communicating the plans to the engineers and fabricators building the brewhouse.

The downsides to the setup? None, except for grain out. The brewery grains in malt by the pallet full, sometimes as much as 4,100 pounds of it if there are a lot of specialty grains in the mix. Spent grain piles up “way above the manway door.” After some sticky situations while getting a feel for the new system, lautering hasn’t been troublesome since adding a simple improvement to the system: a flow meter for the water going into the tun. Dozark says a key part of their process is underletting the grain at mash in—a technique that’s not commonly used unless a mash gets stuck. Dozark pumps water under the false bottom of the big vessel until the grain begins to lift up. It takes a full four barrels of water to create the frothing, floating mash that will prevent the grains from compressing during lauter.

Cooking Longer

While Side Project and Cycle have upsized their mashing equipment to meet the demands of ultra-dense wort, it isn’t the only way to get gravity readings above 30°P (SG 1.1292).

The brewers at WeldWerks in Greeley, Colorado, didn’t start off to make boundary-pushing brews, but one brew changed their trajectory and forced them to get creative with their process to meet demand. Arne Garlick, director of brewing operations, summarizes their brute-force approach to making big stouts on their “traditional, old-school,” 15-barrel brewhouse: “We work the hell out of it.”


He’s not kidding: Producing the 36°P (SG 1.159) wort for the brewery’s signature Medianoche stout takes the first runnings of three full mashes—each technically over capacity—collected over two days. Meanwhile, boiling is continuous for 36 hours. Besides concentrating the first runnings of mid-20s°P (roughly SG 1.100–1.110), the long boil also produces additional flavors from caramelization.

These constraints on throughput are intrinsic to the depth of flavor in the finished Medianoche, Garlick says, and customers can’t get enough. The brewery keeps three fermentors full of Medianoche, brewing it every 10 to 12 days to keep up with demand. Grain out and clean up are the biggest challenges of the lengthy process, but Garlick says it’s worth the trouble. Besides making Medianoche, the team uses these processes to get more capacity out of the brewhouse by brewing high-gravity wort that can be diluted to make different standard-strength beers and bases for barrel-aging projects.


The dual kettle design of Main & Mill Brewing’s 20 bbl production brewhouse is specifically designed for brewing beers with the second runnings from their bigger stouts.

Making Your Bed

There are a few tricks to running maxed-out mash tuns, and rice hulls are the first tool in the box. Rice hulls help prevent the dreaded stuck mash that can occur when the grain bed becomes too compacted for wort to flow out of the mash tun.

“I call it my insurance policy,” says Brad Clark, founder of Private Press Brewing in Santa Cruz, California. He previously was the brewing operations director at Jackie O’s Pub and Brewery in Athens, Ohio, where imperial stouts are often on the brew schedule.


Mash tun modifications are another tool in the box. A mash tun typically has a single side port for lautering, located just above the top of the grain bed of a standard brew. However, when grain beds get extremely deep on high-gravity mashes, the flow from the inlet during lauter can disrupt the carefully managed bed. While at Jackie O’s—a brewery where extreme brews coexist with standard-strength ales—Clark modified the mash tun when the brewhouse was upgraded from the original seven-barrel brewpub system. He added two more side ports to his mash tun—one below the standard port for lower-gravity brewing, and another one higher up, for maximum grain load. It’s a modification that can be retrofitted to existing, unjacketed mash tuns with some simple fabrication, fixtures, and butterfly valves. It also adds to the flexibility of equipment that was once seen as one-size-fits-all.

“I want to lauter just above the grain bed and get a gentle flow across the surface without disturbing the bed,” Clark says.

Brewing enzymes can also help keep things running; beta-glucanase, for example, reduces the wort’s viscosity by breaking down gummy proteins (beta-glucans) that can develop in a mash. At Moksa Brewing in Rocklin, California, Head Brewer Derek Gallanosa relies on enzyme additions to keep a maxed-out mash tun from sticking during lauter. He injects the enzyme into the bottom of the grain bed through a hose pushed in from the top of the mash tun. It helps to keep the mash from compacting, and along with a careful building of the grain bed—from the bottom to top, he layers base malt, specialty malt, and adjuncts from lightest to darkest, topping it off with two more bags of two-row—he can avoid a stuck mash.

Parti Plans

Getting as much sugar as possible into the wort means taking some hits on brewhouse efficiencies, but one brewery south of St. Louis has a novel approach to getting the most beer out of their grists: parti-gyle brewing. This is a decidedly old-school technique where multiple beers are made from a single mash—usually a higher-strength beer from the first runnings and lower-strength styles from the less-sugary second, or even third, runnings. (For more about parti-gyle brewing, see “Practical Parti-Gyle Brewing,”[] At Main & Mill Brewing in Festus, Missouri, they designed the brewing system with parti-gyle brews in mind and an eye toward flexibility.

“We get as much out of our grain as we can,” says cofounder Denny Foster. The new setup is a big improvement, he says, over the old seven-barrel brewpub kit where making big stouts meant 22-hour brew days. Installed in early 2020, the 20-barrel system from Alpha Brewing Industries includes not only a separate oversized mash mixer and lauter tun, but also two kettles. First runnings are drawn off into one kettle while later runnings of weaker wort are sent into the other kettle. They can repeat the mash to double the wort volume in each kettle.

“We’re still getting our feet under us on the new system, but our brew days are now 14 hours instead of almost 24 hours,” Foster says. The end results are two different but related beers. When brewing an imperial stout, the smaller stout usually hits about 5 percent ABV while still containing a lot of flavor—very handy for filling out the brewpub’s tap list with a variety of house beers. “They also work as marketing for the big stouts,” Foster says. Since the small stouts are ready to serve more quickly than their high-gravity counterparts, they give drinkers a sneak-peek (or sneak-taste) of the next imperial stout release. “It builds excitement, and that keeps us excited.”

All of the extra work, extra headaches, and extra costs associated with brewing these extra-big imperial stouts add up. Yet all the downsides seem to pale compared to the kinds of challenges that brewers relish and to the satisfaction of building brands that rouse the kind of fervor and customer engagement that can buoy a business. And as long as crowds gather for them, there will be no shortage of brewers to step out on the highwire of ultra-high-gravity brewing.