Mastering the Mash: Liberate the Soul of Beer from Its Starchy Origins

From our Illustrated Guide to Homebrewing: For those jumping into all-grain brewing at home, here’s what to know about mashing for success.

Dave Carpenter Aug 13, 2023 - 21 min read

Mastering the Mash: Liberate the Soul of Beer from Its Starchy Origins Primary Image

“This—this is merely my way—Where is yours?” I thus answered those who asked about The Way. “For The Way does not exist!”
— Friedrich Nietzsche, Also sprach Zarathustra


Mashing grain is what makes beer beer. Yes, hops, yeast, and water certainly play important roles, but it is only through the mash, whether performed in your house or in the process of manufacturing malt extract, that the soul of beer is liberated from its starchy origins.

Mashing grain is to beer as crushing grapes is to wine, as pressing apples is to cider, and as collecting honey is to mead. It is the fundamental process that makes beer possible, the method by which brewers use naturally occurring enzymes in malted barley to convert starches into fermentable sugars.


In this chapter, we cover the basics of mashing your own grain. Much more can be (and has been) written on this topic than we could possibly begin to cover here, but the lessons you learn here will get you off on the right foot and serve you well for many batches to come.

What the Mash Does

What happens when hot water and crushed grain come together is incredibly complex, and this book is far too brief to even attempt an in-depth treatise on mashing grain. But just as one need not understand the workings of the internal combustion engine to drive a car, one needn’t necessarily understand every aspect of mashing grain to make great beer.

Several processes are at work during the mashing of malt, but the number one process you need be concerned with is the conversion of starches to sugars. And this conversion comes down to two fundamental enzymes:

  • Alpha amylase (α-amylase)
  • Beta amylase (β-amylase)

Alpha amylase does its best work in the 150–160°F (66–71°C) temperature range. It converts complex starches into long chains of sugars. Yeast doesn’t readily ferment such sugars, so a mash temperature that favors alpha amylase tends to create less fermentable wort, which leaves residual body and sweetness in the final beer.


Beta amylase is most active in the 130–150°F (54–66°C) temperature range. It works by snipping the ends off long-chain sugars to create simpler sugars. Yeasts can easily ferment these simple sugars, so a mash that favors beta amylase will yield more fermentable wort, giving the final beer a drier finish and thinner body.

Thus, adjusting the mash temperature warmer or cooler affects the body and sweetness of the final beer by favoring alpha or beta amylase, respectively. If you really get into all-grain brewing, you’ll encounter plenty of other enzymes, but these are the only two you need to know about to get started.

Crushing Grain

Malt needs to be milled, or crushed, before it can be mashed to extract fermentable sugars. In general, finely crushed malt yields better efficiency than coarsely crushed malt, but this isn’t the whole story. The outer husks of barley kernels are an important part of the lautering (wort separation) process, so you want to keep those as intact as possible.

A crush that is too fine turns the internal starch into flour and shreds the barley husks into small pieces. A fine crush boosts extract efficiency, but the damaged husks are less able to filter the wort, making lautering difficult. Too coarse a crush causes the opposite problem. Intact barley husks make for easy lautering, but the starchy endosperm remains intact as well, which means that alpha and beta amylase can’t easily get to the starch.


A good crush, therefore, strikes a compromise, combining acceptable extract efficiency with good lautering properties. It minimizes the sizes of the crushed starch kernels and maximizes the sizes of the husks. The malt mill at your homebrew store is probably set to strike this compromise. If you have a malt mill at home, you can experiment with various settings to achieve the perfect compromise for your system.

Commercial breweries often wet mill their malt, which involves hydrating dry malt with hot water or steam as it enters the mill. This makes the malt husks more pliable, which helps them remain intact as the starchy endosperm is crushed into fine pieces. You can achieve similar results by spritzing your malt with a spray bottle 20 minutes or so before crushing it. Just give the malt a good mist, stir, and repeat until it feels slightly moist. Not wet, just damp—“less dry,” even. Then crush your malt as usual.


Brewers create different kinds of wort by following what is called a mash schedule, mash regimen, or mash protocol. With knowledge of how different enzymes work, an advanced brewer can favor each enzyme for varying lengths of time. A mash schedule is just a timetable of different temperature steps, called rests, and how long each rest should be held.

Single-Temperature Infusion Mashing

Most all-grain homebrewers (and, for that matter, most American and British craft brewers) depend almost exclusively upon the single-temperature infusion mash. It’s all you need to brew most styles of beer with well-modified malts (see Chapter 2 for more about malt modification).


In a single-infusion mash, you add (infuse) a specified quantity of hot water to crushed malt to achieve a specific mash temperature. The mash is held at that temperature for an hour or so, then the mash is complete. Changing the temperature of the mash changes the fermentability of the wort. As I discuss above, a temperature of 146–152°F (63–67°C) favors beta amylase, yielding wort that is relatively dry and light-bodied. A low mash temperature is perfect for many Belgian ales and refreshing summer lagers.

A mash in the range of 152–158°F (67–70°C) favors alpha amylase, which results in beer with lots of body and residual sweetness. A high mash temperature is ideal for any beer where a thick, viscous body is desired, including many British styles and so-called “session” beers.

Most of the beer you make will use a rest around 152–154°F (67–68°C), which offers a good compromise of beta amylase and alpha amylase activity. This is a great temperature to aim for if you don’t want to think about it too much.

Multistep Temperature Mash

In a multistep temperature mash, the mash is carried through a series of rests, or temperatures, that are held for a certain period of time. A typical mash regimen might include the following:

  • A protein rest at 113–130°F (45–54°C)
  • A beta amylase rest at 140–150°F (60–65°C)
  • An alpha amylase rest at 160–165°F (71–74°C)
  • Mash-out at 170°F (77°C)

Such a mash protocol is most appropriate when the malt isn’t fully modified or for brewers interested in German brewing practices. Homebrewers who want to execute a stepped temperature mash typically use a direct-fired mash tun or similar vessel to raise the mash temperature through the various steps. With some planning, homebrewers who mash in an insulated cooler can pull off a multistep mash by adding infusions of boiling water to achieve the steps.

Mashing Logistics

Strike water is the name given to the brewing liquor that is mixed with the crushed grain to start the mash. Typically, strike water is heated to several degrees above the target mash temperature. The precise temperature of the strike water depends on the temperature of your grain, the temperature of your mash tun, and even the mash tun shape, size, and material.

It’s worth the small outlay of cash to purchase good-quality brewing software to help you make these calculations. But when you’re just getting started, estimating a strike temperature that’s about 10–15°F (6–8°C) hotter than your intended mash temperature should get you close. When your strike water has reached the right temperature, it’s time to mash in. Rather than add all of the grain and water to your mash tun at once, I recommend combining them in stages:

1. Add half the strike water to the mash tun.
2. Add half the crushed grain and stir well to mix.
3. Add the remaining strike water to the mash tun.
4. Add the remaining grain and stir well to mix.


After you’ve mashed in, let the mash rest for 5 minutes, then check the temperature. If it’s too low, add some boiling water to raise it. If it’s too high, toss in a handful of ice cubes to lower it. The mash tun should maintain the temperature throughout the mash, so once it has stabilized, there’s no need to keep checking.

Don’t worry if your mash comes in a couple of degrees low or high. With experience you’ll learn how to predict this. For now, as long as your mash is somewhere between 150°F (66°C) and 155°F (68°C), that’s good enough.

About 20 minutes before the mash is finished, start heating sparge water (more about the sparge in the next chapter). The amount of sparge water you need changes from one batch to another, so always heat a little more than you think you’ll need. The target temperature for sparge water is 168–170°F (75–77°C).

When Is the Mash Complete?

Many homebrewers make great beer without ever checking that the mash has fully converted. If you buy crushed malt from your local homebrew store and ensure that the mash temperature remains within a few degrees of the target temperature, then an hour-long mash should result in sufficient conversion in most cases.


Nonetheless, if you’d like to check for conversion, doing so is simple. You need some tincture of iodine (available at drugstores) or some undiluted Iodophor sanitizer:

1. Remove a small sample of wort from the mash tun and place it on a white saucer, taking care to remove only liquid and no grain material.
2. Add a single drop of iodine or Iodophor to the wort sample and mix thoroughly.
3. If the iodine turns black, a good deal of residual starch remains in the mash, and you should leave it for another 15–30 minutes. If the iodine remains yellow-red, then the starches have been fully converted.

The color can be difficult to discern for dark wort (such as stout), and the iodine test is far from perfect. But if you’re nervous about conversion, it may help reassure you.

A Few Notes on Water

Water chemistry is a topic unto itself and can easily fill an entire volume. (In fact, it does. See Water: A Comprehensive Guide for Brewers by John Palmer and Colin Kaminski.)


But water quality is crucial to all-grain brewing, so you can’t ignore it altogether. A few styles such as Czech Pilsener, Irish stout, and Burton IPA may benefit from a sophisticated understanding of water chemistry. But it’s better to start simply and adjust your process as you gain experience than to worry about water from the outset.

Resist the temptation to start adding this and that to your water because you read somewhere that Burton water has so many parts per million (ppm) of sulfate, and yours only has 4 ppm. Tweaking ions certainly affects the flavor of your beer, but this should be a secondary consideration to mash pH.

Mash pH

The pH is roughly a measure of how acidic a substance is. To understand pH as a beginning brewer, you need to know only four things:

  • A solution with a pH of less than 7 is said to be acidic.
  • A solution with a pH of exactly 7 is said to be neutral. Pure water has a pH of 7.
  • A solution with a pH higher than 7 is said to be basic.
  • The optimal pH for a mash of malt and water is in the range of 5.2–5.6.

Chemists can dig into textbooks to understand why this is the case. The rest of us need only remember that when we measure the pH of a mash, we want it to be in the 5.2–5.6 range. Given this ideal range and given that dissolved substances can affect that pH, our main goal as brewers is to ensure that the blend of dissolved ions and molecules results in a mash pH that’s in our target range. And the two biggest players are calcium and bicarbonate:

  • Calcium (Ca) generally lowers mash pH. It helps alpha amylase work better at starch conversion. It even aids in settling trub and yeast at the end of fermentation. You want calcium on your side.
  • Bicarbonate (HCO3-1) generally raises mash pH. It reduces fermentability. And it discourages sedimentation. In other words, bicarbonate is not usually your friend.

At the risk of oversimplifying a very complex situation, calcium and bicarbonate play opposite roles. By tweaking these two ions, you can often move a mash pH into the desirable range of 5.2–5.6. Here, then, is the approach I recommend you take to brewing water as a beginning homebrewer.

  • Obtain a city water report or purchase clean, uncomplicated water if your tap water is unsuitable. You don’t know where you need to go if you don’t know where you start!
  • Determine whether your water, combined with the grain you intend to mash, falls into the pH range of 5.2–5.6.
  • Treat your water to move the mash pH where you want it.

If your tap water is very low in mineral content, congratulations! You can brew just about anything you like by adding things to it. If, on the other hand, your tap water has a very high concentration of dissolved substances, just start with distilled or reverse osmosis (RO) water that you purchase from the store.
Remember that it’s the mash pH that matters, not the pH of the water you add. Most water has a pH greater than 7, while grain malts contribute acidity. Generally speaking, the darker the grain, the more acidity it will lend to the mash. Very light malts, however, may not be acidic enough to get the pH of the mash down into that 5.2–5.6 range.

The most accurate and easiest way to measure mash pH is to invest in a digital pH meter. However, pH meters don’t come cheap, and they can be somewhat fussy in terms of maintenance, requiring periodic calibration. A decent alternative is to use pH test strips designed for brewing. Simply dunk the end of the strip into your mash and compare the resulting color against a scale on the side of the package. It’ll get you in the ballpark.

How to adjust pH

The following additions can be used to acidify the mash (lower pH):

  • Gypsum (CaSO3) is best used in styles that benefit from hard water. Think Irish and English ales, including Irish stout and Burton IPAs.
  • Calcium chloride (CaCl2) is more neutral and is the preferred way to introduce calcium without also adding sulfate.

If you happen to need to raise the mash pH, then turn to these:

  • Baking soda (NaHCO3) raises mash pH and contributes sodium.
  • Chalk (CaCO3) can also raise the pH, but it’s not as effective as baking soda. However, it’s good to consider in cases where baking soda might lend too much sodium.
  • Calcium hydroxide (Ca(OH)2) must be handled carefully, but it is very effective at raising mash pH. Look for pickling lime in the canning section of your supermarket or cal in Latin markets—it’s the substance involved in the nixtamalization of maize to make masa harina.

If your overall water profile looks good, but you’re having trouble hitting the desired mash pH, you can also adjust mash acidity using other kinds of products.

  • Sauermalz, or acidulated malt, is a German pilsner malt that has been acidified using naturally occurring Lactobacillus bacteria. The German Reinheitsgebot prohibits water additions, but Sauermalz can drop the pH without such additions. Simply substitute a portion of the base malt with Sauermalz. Roughly speaking, a grist containing 1 percent Sauermalz will experience a 0.1 drop in pH. Two percent drops the pH by 0.2, and so on.
  • Lactic acid is available in an 88 percent pure form from most homebrew stores. Only a few drops are needed, and it’s very effective. Add a drop or two, stir the mash, and test the pH.


Chlorine has done wonders for modern sanitation and is incredibly effective at eliminating waterborne pathogens such as cholera. Unfortunately, chlorine can interact with compounds found in malt and create dull, plastic-like flavors in your beer. If you start with bottled water, then you don’t need to worry about chlorine, but those who draw from municipal sources may need to take steps to eliminate it.

The easiest way to remove chlorine from your brewing water is to simply draw your water from the tap the day before you plan to use it and let it stand overnight. Chlorine will naturally escape into the air. Boiling accelerates this evaporation.


Unfortunately, many municipalities have switched to using a combination of chlorine and ammonia, which react to create what are known as chloramines. An effective way to reduce chloramine levels in your water is to add potassium metabisulfite, also known as Campden tablets. Usually half a tablet will do the trick for a 5-gallon (19 l) batch.

To use a Campden tablet to remove chloramines from your tap water, draw the entire volume of water that needs to be treated, including mash, sparge, and top-up water. For a 5-gallon (19 l) batch, this is usually around 8–10 gallons (30–38 l), depending upon the grain bill (more grain means more water lost to absorption). Crush half a Campden tablet into powder and add it to the water. The reaction takes only a couple of minutes, but just to be safe, wait for 5 to 10 minutes before you begin heating the water for mashing and sparging.

Moving On

Once your mash has completed conversion, it’s time to move on to the next step: lautering. This is the process by which we separate the barley sugar water from the spent grain and collect it for brewing.

This is an excerpt from our Illustrated Guide to Homebrewing by Dave Carpenter. Want to read the whole thing? Download it here.