Section 3 – Brewing All-Grain Beer
Chapter 16 - The Methods of Mashing
In chapters 14 and 15 you learned about the chemistry in the mash tun. In this chapter we will discuss how to physically manipulate the mash to create a desired character in the wort and the beer. There are two basic schemes for mashing: Single Temperature—a compromise temperature for all the mash enzymes, and Multi-Rest—where two or more temperatures are used to favor different enzyme groups. You can heat the mash in two ways also, by the addition of hot water (Infusion) or by heating the mash tun directly.
There is also a combination method, called Decoction Mashing, where part of the mash is heated on the stove and added back to the main mash to raise the temperature. All of these mashing schemes are designed to achieve saccharification (convert starches to fermentable sugars). But the route taken to that goal can have a considerable influence on the overall wort character. Certain beer styles need a particular mash scheme to arrive at the right wort for the style.
Author’s Note 2025: While the above statements about multiple rests and decoction are still true in theory, in actual practice the vast majority of craft brewers produce all of their beers using a single infusion mash. Why? Because with today’s well-modified malts – it works – even for lagers. So, keep this in mind as you read all about the different mash methods. If you want to do multi-temperature decoctions for the fun of it, that’s fine, but you don’t have to.
Single Temperature Infusion
This method is the simplest and does the job for most beer styles. All of the crushed malt is mixed (infused) with hot water to achieve a mash temperature of 150–155°F (65-68°C), depending on the style of beer being made. The infusion water temperature varies with the water-to-grain ratio being used for the mash, but generally the initial “strike water” temperature is 10–15°F (5-8°C) above the target mash temperature. The equation is listed below in the section, “Calculations for Infusions.” The mash should be held at the saccharification temperature for about an hour, hopefully losing no more than a couple degrees. The goal is to achieve a steady temperature.
The best way to maintain the mash temperature is to use an ice chest or picnic cooler as the mash tun. This is the method I recommend for the rest of the book. Instructions for building a picnic cooler mash/lauter tun are given in Appendix E.
Generally I recommend a water to grist ratio of 1.5-2 quarts per pound (3-4 liters per kilogram), and a strike water temperature of 160-165°F (70-74°C). It may help to start out with a lower grist ratio of 1.5 qts./lb. (3 L/kg) in case you undershoot the target temperature. If at first you don’t succeed, you can add more hot water according to the infusion calculations to make up the difference. It is always a good idea to heat more water than you think you’ll need in case your mash temperature comes out lower than expected. Pre-heating the mashtun with hot water will help you achieve your predicted temperatures more consistently.
Multiple Rest Mashing
A popular multi-rest mash schedule is the 104–140–158°F (40–60–70°C) mash, using a half hour rest at each temperature, first advocated for homebrewers by George Fix. This mash schedule produces high yields and good fermentability. The time at 104°F (40°C) improves the hydration of the mash and promotes enzyme activity.
As can be seen in Figures 91 and 92—Enzyme Ranges, several types of enzymes are at work, liquefying the mash and gelatinizing the starches in the endosperm. Varying the times spent at the 140°F (60°C) and 158°F (70°C) rests allows you to adjust the fermentable sugar profiles. For example, a 20 minute rest at 60°C, combined with a 40 minute rest at 70°C produces a sweeter, more dextrinous beer, while switching the times at those temperatures would produce a drier, more attenuated beer from the same grain bill. You can also change the rest temperatures to change the profiles. For instance, you could rest at 145°F (63°C) and 155°F (68°C) to improve gelatinization and beta amylase activity to make a more attenuable wort.
If you use a moderately-modified malt, such as Briess Pilsen malt, a multi-rest mash will produce a better yield than a single infusion. These malts often need a protein rest to fully realize their potential. The mash schedule suggested by Fix in this case is 122–140–158°F (50–60–70°C), again with half hour rests. The rest at 122°F (50°C) takes the place of the hydration rest at 40°C and provides the necessary protein rest. This schedule is well suited for producing continental lager beers from moderately-modified malts. These schedules are provided as guidelines. You, as the brewer, have complete control over what you can choose to do. Play with the times and temperatures and have fun.
Multi-rest mashes require you to add heat to the mash to achieve the various temperature rests. You can add the heat in a couple of ways, either by infusions or by direct heat. If you are using a kettle as a mash tun, you can heat it directly using the stove or a stand-alone hotplate. (See Figure 98)
The first temperature rest is achieved by infusion using the single temperature mash method described above. The subsequent rest(s) are achieved by carefully adding heat from the stove and constant stirring to avoid scorching and heat the mash uniformly. After the conversion, the mash is carefully poured or ladled from the mash tun into the lauter tun and lautered. The hot mash and wort is susceptible to oxidation from hot side aeration (HSA) due to splashing at this stage, which can lead to long-term flavor stability problems.
If you are using a picnic cooler for your mash tun, multi-rest mashes are a bit trickier. You need to start out with a stiff mash (e.g. .75–1 quarts per pound of grain or 1.5-2 liters per kilogram), to leave yourself enough room in the tun for the additional water. Usually only 2 temperature rests are possible with this method because the amount of heat necessary to change the temperature of the mash increases with each addition. Reaching a third rest is possible if the change in temperature is only a few degrees. For example, raising the mash temperature for 8 lbs. of grain from 150°F to 158°F at a mash ratio of 2 quarts per pound would require approximately 2.7 quarts of boiling water.
Infusion Calculations
(updated 2025)
These calculations allow you to estimate the amount of heat provided by a volume of hot water so you can predict how much that heat will change the temperature of the mash. This method makes a few simplifications, one of which is the assumption that no heat will be lost to the surroundings, but we can minimize this error by pre-heating the tun with some boiling hot water. Pour a gallon or two of boiling water into your cooler (before you add the grist), swirl it around and let it sit for a few minutes with the lid on, and then dump it. By preheating the cooler just before you add your grist and strike water, most of the infusion heat will go to the grist rather than the cooler, and you infusion calculations will be more accurate.
Most of the thermodynamic constants used in the following equations have been rounded to single digits to make the math easier. The difference in the results is at most a cup of hot water and less than 1°F. Experience has shown the equation to be fairly reliable and consistent batch-to-batch, as long as you pre-heat the tun.The calculation for the initial infusion only depends on your initial grain temperature, the target mash temperature, and the ratio (R) of water-to-grain in quarts per pound. The amount of grain is taken into account in the ratio.
These equations also work for liters, kilograms and degrees Celsius. The thermodynamic constant 0.4 doesn’t change because it means that the grain has 40% of the heat capacity compared to the water.
Dry Grain Infusion Equation Strike Water Temperature Tw = (.4/R)(T2 - T1) + T2
Mash Infusion Equation Wm = G(.4 + R) (T2 - T1)/(Tw - T2)And Volume of water, Wv = Wm/⍴where:G = The amount of grain in the mash (in pounds or kilograms).R = The weight ratio of water to grain liters/kilogram. Wm = The weight of boiling water added (in pounds or kilograms).Wv = The volume of water added (in quarts or liters).⍴ = density of hot water (2.055lbs/qt. or 0.985 kg/L)T1 = The initial temperature (°F or °C) of the mash.T2 = The target temperature (°F or °C) of the mash.Tw = The actual temperature (°F or °C) of the infusion water.The infusion water does not have to be boiling, a common choice is to use the sparge water at 170°F (77°C). Then Tw becomes 170°F and more water will be needed to make up the additional quantity of heat. But it works better with hotter water.
Multiple Rest Infusion Example
This example will use three rests. We are going to mash 10 lbs. (4.54 kg) of grain at an initial volume ratio Rv of 1 qt/lb., through a 122°F, 149 °F, and 158 °F (50, 65, and 70°C) multi-rest mash schedule. For the purposes of this example, we will assume that the temperature of the dry grain is 70°F (21 °C). The first infusion will need to take the temperature of the mash from 70°F to 122°F (21 to 50°C). Remember, you may want to add one or two degrees to these targets to account for heat lost to the tun, but I will not do that for these examples.
1. We will start with an initial water to grist ratio (Rv) of 1 qt/lb. Using Table XX, this equates to R of 2.06. This means that we will use about 10 quarts or about 9.5 liters for the volume of the initial infusion. Note that R (w/w) is unitless and does not need to be converted when switching to liters and kilograms. Vw = G x R/ρ = 10 x 2.06/2.055 = 10 quarts Vw = G x R/ρ = 4.54 x 2.06/.985 = 9.5 litersUsing the single infusion equation, the strike water temperature is: Tw = (0.4/R)(T2-T1) + T2= (0.4/2.06)(122 - 70) +122 = 132°F= (0.4/2.06)(50 - 21) +50 = 55.6°C
2. For this example, we will assume our mash has not lost any heat during the rest and is still at 122°F (50°C). In reality, you should measure the temperature and use that value as T1 in the equation. Our mash currently contains 10 quarts (9.5 L) at a water to grist ratio of 2.06. We need to use the mash infusion equation for the second infusion to raise the temperature to 149 °F. We will assume that our boiling hot water for the infusions has cooled somewhat to 205 °F (96°C). Wm = G(S + R)(T2 - T1)/(Tw - T2)Wv = Wm/ρ Wm = 10(.4 + 2.06)(149 - 122) ÷ (205 - 149) = 11.86 pounds of hot waterWv = Wm/ρ = 11.86/2.055 = 5.8 quartsWm = 4.54(2.46) x (65 - 50) ÷ (96 - 65) = 5.4 kgWv = Wm/ρ Wv = 5.4/.985 = 5.48 liters
3. For the third infusion, the total water volume is now 10 + 5.8 = 15.8 qt. We need to recalculate R. The current mash temp is 149°F (65°C), and the target is 158°F (70°C). The temperature of the infusion water is still 205°F (96°C). R = (Wv x ρ) /G = 15.8 x 2.055 ÷ 10 = 3.25 Wm = G(.4 + R)(T2 - T1)/(Tw - T2)Wv = Wm/ρ Wm = 10(3.65)(158 - 149) ÷ (205 - 158) = 6.99 pounds of hot waterWv = Wm/ρ = 6.99/2.055 = 3.4 quartsWm = 4.54(3.65) x (70 - 65) ÷ (96 - 70) = 3.19 kgWv = Wm/ρ Wv = 3.18/.985 = 3.24 liters The total volume of water required to perform this schedule is:10 + 5.8 + 3.4 = 19.2 qt, or 4.8 gallons.The final water volume to grain ratio has increased to 1.92 qt/lb (19.2 ÷ 10). The final weight to weight mash ratio is :10 x 2.055 + 11.86 + 6.99 = 39.4/10 = 3.94 Note to Liters, Kilograms, °C natives: If you had been conducting this mash from the beginning using the same amount of grain (4.54 kg) but using liters, your nominal Rv would have been 2 liters per kilogram, and your R (w/w) would have been 1.97 . R for the second infusion would have been 3.11, and the final R would have been 3.79. These differences demonstrate that while 2 quarts per pound is very similar to 4 liters per kilogram, they are not exactly the same.
3. For the third infusion, the total water volume is now 10 + 5.8 = 15.8 qt. We need to recalculate R. The current mash temp is 149°F (65°C), and the target is 158°F (70°C). The temperature of the infusion water is still 205°F (96°C). R = (Wv x ρ) /G = 15.8 x 2.055 ÷ 10 = 3.25 Wm = G(.4 + R)(T2 - T1)/(Tw - T2)Wv = Wm/ρ Wm = 10(3.65)(158 - 149) ÷ (205 - 158) = 6.99 pounds of hot waterWv = Wm/ρ = 6.99/2.055 = 3.4 quartsWm = 4.54(3.65) x (70 - 65) ÷ (96 - 70) = 3.19 kgWv = Wm/ρ Wv = 3.18/.985 = 3.24 liters The total volume of water required to perform this schedule is:10 + 5.8 + 3.4 = 19.2 qt, or 4.8 gallons.The final water volume to grain ratio has increased to 1.92 qt/lb (19.2 ÷ 10). The final weight to weight mash ratio is :10 x 2.055 + 11.86 + 6.99 = 39.4/10 = 3.94 Note to Liters, Kilograms, °C natives: If you had been conducting this mash from the beginning using the same amount of grain (4.54 kg) but using liters, your nominal Rv would have been 2 liters per kilogram, and your R (w/w) would have been 1.97 . R for the second infusion would have been 3.11, and the final R would have been 3.79. These differences demonstrate that while 2 quarts per pound is very similar to 4 liters per kilogram, they are not exactly the same.
Figure 98—Mashing in the kitchen — The grist is added to the cooler and infused with the strike water to bring the mash temperature to the desired rest temperature. Additional boiling water can be added to raise the temperature to a second rest, if desired. During the mash, sparge water is heated on the stove. After mashing, additional water is added (if necessary) to bring the wort volume to half of the intended boiling volume, and the first runnings are drained to the boiling pot. The sparge water is then added to the mash tun, stirred thoroughly, and allowed to steep for 15 minutes before recirculation and draining. The full wort is then placed on the stove and boiled with the hops.
Figure 99 - Oh the anachronism! In the early 2000's, Volkswagen had a marketing campaign with the slogan, "Fahrvergnügen" which means, "the joy of driving". I borrowed the design to create this image to indicate the "joy of 3 step decoction". I like it.
Figure 100—Use this diagram to help you plan your decoction mash. If you are going to do a Zweimaischverfahren, start at the Double Decoction box and infuse your mash with hot water to achieve a protein rest. Next, pull your first decoction according to the decoction step description, and add it back to your mash to achieve the conversion rest. Then pull your second decoction according to its description to achieve mashout. Use the measuring cup or a saucepan to transfer the decoctions. You can use the decoction calculations presented on the next pages or just wing it and watch your thermometer. Good Brewing!
To Rest, or Not to Rest, That is the Question...
When should you do a protein rest?
A protein rest is done for two reasons: to improve the breakdown of the endosperm in less-modified malts, and to increase the FAN in high adjunct worts. Malts with an S/T ratio or Kohlbach Index of 36-40% benefit from a protein rest to further degrade the protein matrix around the starches of the endosperm. If the S/T ratio is less than 36%, then a longer protein rest and the boiling action of a decoction mash will probably be necessary to fully release the malt starches into the mash.
You can also do a protein rest in mashes with a high proportion adjunct (>30%) of unmalted wheat, oats, or rye in the mash. Unmalted starch adjuncts like wheat, oats, and rye contain little soluble protein that can be converted to FAN. Corn (maize) and rice contain very little protein at all. A protein rest helps provide more soluble protein and FAN to the wort that will actually improve head retention and promote a healthy fermentation. Protein rests are common practice in well-modified, high adjunct commercial brewing.
If you do a protein rest on a well-modified all-malt beer, you will not ruin it, but you are really not helping it either. A really long protein rest, for over 30 minutes, could potentially degrade too much of the foam-positive soluble protein into amino acids to have the best head retention, but it will not be “ruined.”
Decoction Mashing
[figure 99 – Zweimaischverfahren]
Equipment Needed: Cooler mash tun 4 gallon heavy stockpot (aluminum preferred) 1 quart Pyrex glass measuring cup ThermometerDecoction mashing was developed to get the best extraction from the old-time Northern European barley strains that depended on overwintering to germinate, and were more difficult to malt and modify. Decoction mashing provided for better breakdown and solubilization of the starches and better extraction from those less-modified malts. Beer connoisseurs claim better malt flavor and aroma from decoction mashing of those malts. These days less-modified malts are hard to find, but decoction mashing is still useful for extracting that extra bit of malt character for bock and Oktoberfest style lagers. In addition, the decoction mashing provides for increased hot break and clarity in the wort. The pH from decoction mashes has been shown to be .1-.15 pH units lower than the same wort from an infusion mash.
Decoction mashing is a good way to conduct multi-step mashes without adding additional water or applying heat to the mash tun. It involves removing a portion of the mash to another pot, heating it to the conversion rest on the stove, then boiling it, and returning it to the mash to raise the rest of the mash to the next temperature rest. The portion removed should be pretty stiff, no free water should be showing above the top of the grain. The decoction should be held at conversion rest temperatures (150-155°F / 65-68°C) for 10-15 minutes before being boiled. Stir contstantly!
You can use a decoction to move to any temperature rest you want, but it was traditionally used to move the main mash from a dough-in rest to the beta glucanase/protein rest, to the conversion rest, to mashout. This three step decoction process is called, “Dreimaischverfahren.” As lager malts became more modified, the dough-in stage was dropped, and the main mash was initially infused to the protein rest temperature. This two step decoction for taking the mash from protein rest to conversion rest, and then to mashout is called, “Zweimaischverfahren.” You can also do a single decoction from conversion to mashout.
According to Greg Noonan, author of The Seven Barrel Brewer’s Handbook, the important thing when brewing for extra malt character is not the number of decoctions, but the time spent boiling (one of the decoctions) to develop the Maillard reactions and flavors. He recommends boiling for 20-45 minutes. What this means to me is that you can use triple decoctions with less-modified malts, double decoction with moderately-modified malts, and single decoctions with well-modified malts to achieve the same degree of extract, and (hopefully) the same sorts of malt flavors, by adjusting the boiling time of the main decoction. Maillard reactions are complex though; you would probably have to experiment a bit to find the flavors you were looking for. See Figure 100 for a diagram of the decoction process and keep your thermometer handy.
For recipes and more insight on when to use decoction mashing, I encourage you to read books like: New Brewing Lager Beer by Greg Noonan, Radical Brewing by Randy Mosher, Designing Great Beers by Ray Daniels, and some of the Classic Beer Styles books by Darryl Richman, Eric Warner, and George Fix.
Decoction Calculations
(updated 2025)
The key difference with decoction mashing is in the way heat is added to the system. With infusion mashing, hot water is always being added to the system. Decoction differs in that a volume of mash is removed from the tun, heated to boiling on the stove, and returned to the tun to raise the mash to the next temperature rest.In essence, the amount of heat needed raise the temperature of the main mash, minus the decoction, has to equal the amount of decoction multiplied by its heat. The equation for estimating the volume of the decoction to pull and add back to the mash is given by:
Vd = Vm x (T2-T1)/(Td-T1)Where: Vm is the volume of the main mashVd is the weight of the decoction, Td is the temperature of the decoctionT2 is the target temperature of the next restT1 is the current temperature of the mash
Note that this equation calculates the volume of the decoction and not the weight. Thermodynamically, weight is the proper factor, but this equation calculates a conservative estimate that provide slightly more decoction to work with than if we had calculated a precise amount based on the relative water to grist ratios of the mash and weight of the decoction. The big unknown in the equation is the total volume of the mash, which can be measured or calculated using the grain weight and the water volume to grist ratio (Rv):
V = G x (R + 0.38) For pounds and quartsV = G x (R + 0.8) For kilograms and literswhere:V = total volume (quarts or liters)G = (dry) weight of grain (pounds or kilograms)Rv = water to grain ratio of the mash (qts/lb. or L/kg)
Vd = Vm x (T2-T1)/(Td-T1)Where: Vm is the volume of the main mashVd is the weight of the decoction, Td is the temperature of the decoctionT2 is the target temperature of the next restT1 is the current temperature of the mash
Note that this equation calculates the volume of the decoction and not the weight. Thermodynamically, weight is the proper factor, but this equation calculates a conservative estimate that provide slightly more decoction to work with than if we had calculated a precise amount based on the relative water to grist ratios of the mash and weight of the decoction. The big unknown in the equation is the total volume of the mash, which can be measured or calculated using the grain weight and the water volume to grist ratio (Rv):
V = G x (R + 0.38) For pounds and quartsV = G x (R + 0.8) For kilograms and literswhere:V = total volume (quarts or liters)G = (dry) weight of grain (pounds or kilograms)Rv = water to grain ratio of the mash (qts/lb. or L/kg)
Adjunct Mashing Procedure
I wanted to open this section with the Monty Python line: “And now for something completely different…” But that’s wrong. It’s actually something completely the same, being just a combination of some of the methods we have already discussed. To brew with starch adjuncts, you need to do is hydrolyze and gelatinize the starches so the amylase enzymes can break them into fermentable sugars. Accessibility is the key. You can gelatinize the starches by just boiling them, but you can do it more effectively by using a combination of enzymes and heat.What about flaked adjuncts like corn (maize) and oats? Aren’t they already pre-gelatinized? Yes, to a degree. Gelatinization is not like being pregnant, it’s like cooking. Actually it is cooking. Instant oats are more gelatinized than old-fashioned rolled oats. Also, just because an adjunct is flaked and pre-gelatinized does not mean that it is fully accessible to the mash enzymes. It helps to grind the rolled flakes too, especially the big flakes like barley, oats, rye, and wheat.
Rice and corn (maize) contain very little beta glucan and protein. There is no need to do a beta glucanase rest when mashing these grains. Unmalted barley has a lot of beta glucan as do unmalted rye, oats, and wheat, and a beta glucanase rest is necessary for good lauterability. If you are using malted wheat, oats, or rye, you don’t need a beta glucan rest, but you will probably want to include a protein rest to break up the higher levels of higher molecular weight proteins these malts contribute if you are using more than 20% in your grain bill. And lastly, you may want to include rice hulls into the mash to help with lautering. The husk of malted barley constitutes about 5% of the weight, so if you are 20% malted wheat (which has no husk) in your brew, you would want to add at least 1% of the total grain bill weight in rice hulls to make up for it. Rice hulls are probably going to be necessary with wheat beers, rye beers, and high adjunct beers like American lager. The corn and rice don’t have the beta glucan that makes lautering difficult, but the high proportion of no-hulls will affect the lauterability all the same. I have not needed rice hulls for oatmeal stouts.
To conduct a cereal mash, I recommend that you use a heavy stock pot that can hold at least 4 gallons. To conduct a cereal adjunct mash:1. If the adjunct is not flaked, then grind it a few times in your roller mill or use small coffee grinder, or a hammer, but you need to break it down for the best results. 2. Combine your cereal grist with about 25% by weight of base malt, and infuse it at a ratio of 2 quarts per pound (4 liters per kg) to the first temperature rest. Barley, oats, rye, and wheat should be started at 113°F (45°C) for a combined beta-glucan and protein rest. (You can cover all your bases that way.) You can start corn and rice at the beta amylase rest of 145°F (63°C). Try not to exceed a 4:1 ratio of adjunct to malt to avoid diluting the enzymes too much. 3. Hold the mash at the beta glucanase rest for about 15 minutes, and then heat it slowly, stirring constantly to get to the conversion rest. Barley, wheat, oats and rye can be fully converted at 155-158°F (68-70°C). Corn and rice will need higher temperatures to assure gelatinization, 165-172°F (74-78°C), but the barley enzymes will convert any pre-gelatinized starch from rolling/flaking.4. Next, bring the mash to a gentle boil for about 10-15 minutes to fully gelatinze all the starches. There should be few if any crunchy bits left.5. The main mash can be infused and waiting at whatever temperature rest is appropriate for your recipe. You can use this hot starch soup as a decoction for your main mash to reach the next rest temperature, or wait for it to cool to the saccharification temperature if you are doing a single rest mash. Keep in mind that you may need a short protein rest for your main mash to generate more FAN if you are using a high proportion of low protein adjunct.6. You can conduct further decoctions as necessary to finish the mash and then add rice hulls as necessary to help lautering. Good Brewing!
Summary
There you have it: the two or three methods of mashing, and the calculations to take out the guesswork. Most brewers keep it simple and use single rest infusion in a picnic cooler. It is the easiest method for producing an all-grain wort. Decoction mashing used to be the hallowed domain of expert all-grain brewers, but it is just another tool that any brewer can use to gain an extra malty edge on a pale wort. The most common homebrewing mash schedule consists of a water-to-grain ratio of 1.5 quarts per pound (3 L/kg) and holding the mash between 150-155°F (65-68°C) for 1 hour. Probably 90% of the beer styles in the world today can be produced with this method. The next chapter describes the different methods for conducing the lauter, i.e., getting the wort out of the grain.