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  • December 12, 2023 5 min read

    Mash Tun: HERMS Electric Brew System Explained

    Part IV Lautering: HERMS Electric Brew System Explained {click here}

    The Mash Tun is a critical component of the Heat Exchange Recirculating Mash System (HERMS), an advanced brewing system used by homebrewers and professional breweries alike. This article delves into the intricacies of the Mash Tun within the context of the HERMS Electric Brew System, providing a comprehensive understanding of its function, design, and operation.

    Understanding the Mash Tun and its role in the HERMS system is essential for anyone looking to elevate their brewing process. By the end of this glossary entry, you should have a comprehensive understanding of the Mash Tun and how it contributes to the overall brewing process in a HERMS system.

    Understanding the HERMS System

    The Heat Exchange Recirculating Mash System (HERMS) is a brewing system that allows for precise temperature control during the mashing process. This is achieved by recirculating the mash through a heat exchanger, typically a coil submerged in hot water, which allows for gradual and controlled heating.

    The HERMS system is comprised of three main components: the Hot Liquor Tank (HLT), the Mash Tun, and the Boil Kettle. Each of these components plays a vital role in the brewing process, and understanding their functions is key to mastering the HERMS system.

    The Role of the Mash Tun in the HERMS System

    The Mash Tun is where the magic of brewing truly begins. It is in this vessel that the brewer combines crushed grains with hot water, a process known as mashing. The purpose of mashing is to convert the starches in the grains into fermentable sugars, which will later be consumed by yeast to produce alcohol and carbon dioxide.

    In a HERMS system, the Mash Tun also plays a crucial role in temperature control. The mash is continuously recirculated through the heat exchanger in the HLT, which allows for precise control over the mash temperature. This is crucial for achieving the desired balance of sugars in the final wort, and ultimately, the flavor and body of the beer.

    Design and Construction of the Mash Tun

    The design of the Mash Tun can vary greatly depending on the specific needs of the brewer. However, all Mash Tuns share some common features. They are typically large vessels, capable of holding several gallons of mash, and are equipped with a false bottom or a similar device to separate the liquid wort from the grain husks.

    The Mash Tun may also include a sparging system, which is used to rinse the grains after mashing to extract any remaining sugars. In a HERMS system, the Mash Tun is also equipped with a recirculation system, which allows the mash to be continuously pumped through the heat exchanger in the HLT.

    Operation of the Mash Tun in a HERMS System

    The operation of the Mash Tun in a HERMS system begins with the mashing process. The brewer adds crushed grains and hot water to the Mash Tun, typically aiming for a temperature between 148°F and 158°F. This mixture, known as the mash, is then allowed to rest for a period of time, typically between 60 and 90 minutes.

    During this rest period, the enzymes in the grains go to work, converting the starches into fermentable sugars. The temperature of the mash is crucial during this stage, as different temperatures favor different enzymes, leading to different balances of sugars in the final wort.

    Recirculation and Temperature Control

    Once the mash has been mixed and is resting, the HERMS system begins to recirculate the mash. The mash is pumped out of the Mash Tun, through the heat exchanger in the HLT, and then back into the Mash Tun. This process gradually and evenly heats the mash, allowing for precise control over the mash temperature.

    The brewer can adjust the temperature of the HLT to control the temperature of the mash. By carefully controlling the temperature, the brewer can influence the balance of sugars in the final wort, and thus, the flavor and body of the final beer.

    Sparging and Lautering

    Sparging in Brau supply mash tun

    Once the mashing process is complete, the brewer begins the process of lautering, which involves separating the liquid wort from the grain husks. This is typically achieved by slowly draining the wort from the bottom of the Mash Tun, while simultaneously rinsing the grains with hot water, a process known as sparging.

    In a HERMS system, the sparging process can be automated, with the system controlling the flow of water and the speed of the drain to achieve an optimal sparge. Once the lautering process is complete, the wort is transferred to the Boil Kettle, where it is boiled and hops are added.

    Maintaining and Cleaning the Mash Tun

    Maintaining and cleaning the Mash Tun is a crucial part of brewing with a HERMS system. After each brew, the Mash Tun should be thoroughly cleaned to remove any residual grains or sugars. This can typically be achieved with hot water and a mild detergent, although some brewers prefer to use specialized brewing cleaners.

    It's also important to regularly inspect the Mash Tun for any signs of wear or damage. This includes checking the false bottom for any signs of warping or cracking, inspecting the recirculation system for any blockages or leaks, and ensuring that all seals and gaskets are in good condition.

    Common Issues and Troubleshooting

    One common issue with Mash Tuns is a stuck sparge, which occurs when the grains form a compact mass that prevents the wort from draining. This can often be resolved by gently stirring the mash, although in severe cases, it may be necessary to remove some of the grains and restart the sparging process.

    Another common issue is temperature fluctuations during the mashing process. This can often be resolved by adjusting the temperature of the HLT, although it may also be a sign of a problem with the recirculation system. If you're experiencing persistent issues with your Mash Tun, it may be worth consulting with a brewing professional or an experienced homebrewer.


    The Mash Tun is a vital component of the HERMS Electric Brew System, playing a crucial role in the mashing process and temperature control. By understanding the function, design, and operation of the Mash Tun, brewers can take full advantage of the capabilities of the HERMS system, producing beers with a wide range of flavors and characteristics.

    Whether you're a seasoned professional or a homebrewing enthusiast, mastering the Mash Tun is a key step on the path to brewing excellence. With the knowledge gained from this glossary entry, you're well on your way to achieving that mastery.

    Ready to elevate your brewing experience with top-of-the-line equipment? Look no further than Bräu Supply, the pioneers of the all-in-one brew system, the Unibräu. Our commitment to quality is unmatched, with every product crafted from premium 304 stainless steel and designed with modularity and electric brewing in mind. Whether you're a home brew enthusiast or a microbrewery aficionado, our Unibräu, Unibräu Pro, and HERMS systems offer unparalleled efficiency and value. Plus, our Unitank fermenters and a vast selection of accessories ensure you have everything you need for a perfect brew. Don't settle for less—check out our products today and discover the Bräu Supply difference!

    Part IV Lautering: HERMS Electric Brew System Explained {click here}

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