Sparge Temperatures, Overcarbonation, Frozen Beer, and Brewing Calculations

Q I’m confused. Sparging is supposed to be done with a grain bed at 170 °F (76 °C). A lot of articles say to use sparge water at 170 °F (76 °C). If mashing is at 152 °F (67 °C), the grain temperature will never get up to 170 °F (76 °C). I’ve been using boiling water to get the grain bed up to 170 °F (76 °C). Is this wrong? What is the correct method?

Barney Heller
North Wales, Pennsylvania

A Hi, Barney. Based on your question I am assuming you are either relatively new to all-grain brewing or starting to question basic practices brewers follow. One thing I wish I knew when I began brewing is that there are lots and lots of different ways to brew great beer. And by extension there are no “correct” methods, just lots of options. Your question mixes best practices from infusion and multi-temperature mashing into a single goal that is out of sync with infusion mashing.

sparge arm during active lautering
Photo courtesy of Paul Mietz Egli

In your case, you are infusion mashing at 152 °F (67 °C). The term “infusion” mash can be confusing because it means different things to different brewers. I like the phrase “isothermal mash” because it leaves no room for miscommunication. German brewers use the term infusion to mean mashing that does not include mash boiling; infusion mashes may be isothermal or stepped mashes covering a broad range of temperatures, with or without a mash-off step. Like I said, this can be a bit confusing.

In a typical isothermal, commercial mash at 152 °F (67 °C), there is no increase in temperature before the onset of sparging because commercial infusion mash tuns are not equipped with heating jackets. The norm is to sparge with water at ~170 °F (76 °C) and allow the mash to heat up to some temperature between 152 °F (67 °C) and 170 °F (76 °C). Why? Because that’s how it’s done! There may be a more reasoned answer than that, but it’s not much different. And the answer is that the hot water tank is maintained at 170 °F (76 °C) because that’s a great strike water temperature for mashes at 152 °F (67 °C) and it’s also really handy to have strike and sparge water stored in the same tank.

Decoctions are always described to be a royal pain, but a single decoction at the end of a single temperature mash is pretty darn easy.

I am sure some readers are thinking about astringency and not wanting to sparge too hot. Yeah, yeah, but what about brewers using stepped mashing and/or decoctions? These brewers typically heat their mashes to ~170 °F (76 °C) at the end of the mash to fully convert the mash, stop enzymes, decrease viscosity, and to boost extract yield. They also sparge with 170 °F (76 °C) water.

Both methods work well and, in practice, infusion mashers usually leave a bit more extract in the spent grain bed for a variety of reasons, including their lower mash temperature during sparging. I like your method because it makes sense and does not just randomly heat up the mash. You are targeting 170 °F (76 °C), achieving your temperature boost with hot water, and then sparging normally.

If you ever want to get a little crazy and uber traditional at the same time, consider boiling about a third of your mash at the end of your rest at 152 °F (67 °C), then mixing this single decoction into your rest mash to achieve your mash-off temperature. Decoctions are always described to be a royal pain, but a single decoction at the end of a single temperature mash is pretty darn easy. And there are several benefits brewers can enjoy including a bump to your extraction yield and it can add some nice malt flavors that isothermal mashing may not lend on its own.

Q When I keg my beer, I force carbonate for two weeks at 14–15 psi. At this time, I have found carbonation is right where I like it and I get just the right amount of head in my glass. This condition lasts until I get about half way though the keg (approximately 11⁄2 months later) when I start getting half beer and half foam. This tends to be worse with hoppier beers. The 14–15 psi is what I calculated to result in 12 psi after pressure loss through my lines. My dispensing lines are about 5–6 feet long. Any ideas what may be causing this?

Marc Kovach
Dover, Pennsylvania

A Your problem is caused by overcarbonation that is slowly occurring over time. Let’s dig into what you are observing over time beginning with your method of carbonation. Based on your question, I am assuming that you are not using the shake and bake method of carbonation where beer is shaken at some pressure to increase the rate of gas absorption. Your method is the set it and forget it method where gas slowly diffuses into beer from the headspace above the beer. I like this method and have no critique of the method. Your problem is your chosen pressure.

Another assumption I am making is that your target carbonation level coincides with the 12 psi at the tap you mention. This is a normal pressure for beers carbonated to 2.57 volumes of carbon dioxide and stored at 38 °F (3 °C) (see the Zahm & Nagel CO2 solubility in beer chart for reference). Carbonating through the headspace is a relatively slow process, where the rate of CO2 flow into beer slows as the dissolved concentration approaches equilibrium with the headspace pressure at whatever temperature the system is set to. In other words, your beer quickly picks up CO2 early in the process, pours well and tastes like you want it to, then it slowly picks up more gas than you want until equilibrium is reached at ~14.5 psi; if your beer is in a 38 °F (3 °C) keezer, the carbonation level is 2.8 volumes of CO2. For readers who prefer g/L of carbon dioxide and bar for pressure, this condition translates to beer at 1 bar
pressure and 5.5 g of CO2 per liter, and for the sake of easy reading I am opting to not repeat this conversion going forward.

If I have misinterpreted your question, hang with me because this general explanation doesn’t have to be correct for the remedy to work . . . but I think I am following what you are doing.

Now let’s look at your draft system. Seems that you have matched your 5–6 feet (1.5–1.8 m) of draft line to match up with 12 psi of pressure; you should be balancing the system to match the equilibrium pressure and temperature of the beer. If you do indeed want 2.8 volumes of carbon dioxide in your beer (great for some styles of beer like weizen or many Belgian-style beers), 14.5 psi at 38 °F (3 °C) is your number. However, your draft line is too short to balance this condition and explains why your beer slowly becomes foamy when poured after a few weeks. In short, your draft system is out of balance. The solution for this particular problem is to increase your draft length to balance the 14.5 psi condition. Based on my explanation above, I don’t believe this is the solution to your problem.

What you need to do is carbonate beer to a typical level of 2.57 volumes (5 g/L) by decreasing your CO2 setpoint to 12 psi (0.8 bar). Assuming you are using 3⁄16-in. ID beer line, your current draft line length fits this system. I am personally a fan of flow-control beer faucets that allow for a bit of fine-tuning when pouring. These faucets provide the best control when the draft line is a bit shorter than calculated because the shorter-than-calculated lines leave a bit of excess pressure to scrub using the flow control faucet. You may find that carbonating to 2.57 volumes takes longer when pressure is reduced to 12 psi, so you may want to do a little beer shaking or rolling the Corny keg to start your carbonation cycle.

Finally, that observation about more challenges with hoppier beers makes sense because these beers often contain very small haze particles from the reaction between hop polyphenols and malt proteins; these little dudes act as nucleation sites for gas breakout during dispense. I hope this helps you solve your dispense issues so that your brews pour properly!

Q My probe accidentally came out of my lagering freezer and I ended up freezing two full kegs of beer. Can they be saved?

Bob Burkhardt
Cameron Park, California

A The good news is that frozen kegs can be saved! I hope you decided to keep your beers, let them thaw, and enjoyed them post arctic chill. Accidentally freezing beers is a common occurrence, even in large and small commercial breweries with, what may seem like, ideal equipment.

Beer freezing can occur from a range of issues. In your case, your temperature probe was somehow pulled from your freezer and your controller did what it is designed to do by telling your freezer’s compressor to keep on chugging. Unfortunately, the controller was operating off of faulty data and continued running until you discovered the issue. Given enough time, the beer in your kegs would freeze to the point where the freeze-concentrated beers’ freezing points equaled the freezer temperature. You’re questioning the effect of freezing on your beers. Well, it depends on what you did after spotting the condition.

Some brewers intentionally freeze-concentrate beer by chilling beer to some temperature where water freezes to ice until the freezing point of the beer equals the environmental temperature (if the vessel is located in a cold environment) or when the beer temperature matches the cooling setpoint and glycol cooling valves shut. So-called freeze point depression and boiling point elevation are examples of colligative properties of water and explain why the freezing point of beer changes as beer becomes more concentrated when water is removed from the liquid system in the form of ice. Your goal was clearly not freezing your beer, but depending on how much ice was removed, you may have decided to convert your beers into unintentional ice beers, whatever that really means!

The traditional ice beer that most brewers know about is eisbock; this style is freeze-concentrated. In the mid-90s, golden-colored ice lagers were all the rage in North America. Labatt developed the Ice Brewing™ process and introduced their Labatt Ice to the world in 1993. This beer contains 5.6% ABV compared to Labatt’s Blue at 5% ABV. U.S. brewers began brewing ice beers shortly after the release of Labatt Ice, but were not permitted to freeze-concentrate beer because of
U.S. law. 

One thing that may have been interpreted as hype with these beers was the smoothness marketed with just about all ice beers. Unlike some marketing, smoothness is actually a thing with ice beer because the cold temperatures and ice crystallization removes polyphenols from beer and reduces astringency. In other words, ice beers have a smoother mouthfeel and finish. The takeaway here is that if you allow your beer to slowly thaw, it very well may end up being improved by the error.

Beer can also freeze because of poorly placed temperature probes or not covering all probes when filling tanks. This is not common for homebrewers, but is a frequently observed occurrence by commercial brewers. How do commercial brewers observe freezing when their tanks are all stainless steel? They see ice chunks in tank bottoms when preparing the tank for cleaning, or hear these ice chunks fall from the tank when racking a tank and hearing large chunks of ice fall from the upper surface of the tank and crash into the bottom of the vessel. In tall tanks, these falling chunks of ice can do real damage to thermal probes and even the bottom of tanks. And many brewers these days have in-line instrumentation or sampling procedures that may reveal freezing. For example, beer color, density, and alcohol readings change when beer is removed from a frozen tank because the top of the tank contains water from melted ice and the bottom of the tank contains beer that is darker in color, more dense, and higher in alcohol than the beer samples at the end of fermentation.

Long story short, frozen beer is not uncommon and allowing a tank to thaw and moving on with your normal brewing process is not the end of the world for affected batches. One freezing scenario that can cause real quality problems is when packaged beer freezes and thaws, especially if there are numerous freeze-thaw cycles. Chill haze, permanent hazes, beta glucan gels, and particulates in the bottom of a bottle or can are some of the things that form in freeze-damaged packages.

Always check on your temperature probe to help prevent similar issues from recurring. Happy brewing and stay chill!

Q An important part of my homebrewing hobby is the development of web-based brewing calculators. The biggest challenge is finding good technical information. Web searches often yield vague results, formulas with errors, or formulas based on non-metric units. Where do professional brewers find high-quality technical information? Which books would you recommend for technical reference purposes? 

Gary Fisk
Americus, Georgia

A I also consider developing my own calculation tools a key part of my hobby and, previously, part of my job as a commercial brewer. I have a pretty handy collection of calculations and will touch on what has been valuable to me along my tool-making journey, starting with your question about sources used by professional brewers. The short answer is brewing school. Whether brewers take brewing classes in universities like Weihenstephan, UC-Davis, KU Leuven, Oregon State, Heriot-Watt, Auburn, and Virginia Tech, or through private brewing schools like Siebel and the American Brewers Guild, the same basic beer math is taught. And these days, it’s all taught using the metric system.

Perhaps the most fundamental group of brewing calculations are those related to wort and brewhouse yield. All schools teach students that kg extract is equal to liters of wort multiplied by the product of wort specific gravity (kg per liter) and wort Plato (kg of extract per kg of wort). This basic relationship opens up a whole set of calculations related to mash calculations and efficiency. Textbooks like Kunze’s Technology Brewing and Malting and The Comprehensive Guide to Brewing (Gabriela Basarová, Jan Savel, Petr Basar, Pavlína Basarová, Tomás Lejsek) include examples of these equations and how they are used. Another really helpful book is Steve Holle’s A Handbook of Basic Brewing Calculations published by the MBAA (Master Brewers Association of the Americas) in 2003.

When it comes to hop math, there is really only one equation universally used and that is how to calculate hop charges based on some level of bitterness in terms of international bitterness units (IBUs). Unfortunately, the golden key that makes hop calculations tick is the elusive utilization term; most brewers refer to tables relating utilization to boil time, wort gravity, and hop preparation type. Some brewers calculate oil contribution based on hop analytics, but this is not commonly used.

There are also a range of brewing calculations related to mashing-in, mash heating and boiling, wort heating, boiling and cooling, and beer blending and dilution. These calculations are all based on fundamental math used in food engineering/processing. Much of this is left out of brewing texts and is the sort of topic often left to classroom lectures. The good news is that Q = MCp∆t is the key to all of the heating and cooling equations (Q is heat energy, M is mass, Cp is specific heat, and ∆t is temperature change). The only obscure constant that can be hard to find is the specific heat of malt. The specific heat of malt and other brewing grains is about 1.8 kJ/kg*Kelvin (0.43 BTU/lb.*F).

Another great source of information about brewing calculations is found on brewing ingredient and process aid specification sheets. My brewing calculation workbook includes separate tabs for usage rates of beer finings, enzymes, and nutrients. These are the sorts of tidbits of information that can easily be added to your library of nuggets as you try new things.

And finally, there is water. I am a picky user of tools and really don’t like any water calculator that I have trialed and wrote my own water tool based on the water basics first laid out by Paul Kolbach in the early 1950s. 

Issue: January-February 2023