Decoction Mash

Whether you’re a seasoned beer meister or a novice homebrewer, you’ve probably heard of using a decoction mash. You may even have a few opinions about it. After all, decoction brewing methods are both ancient and controversial. So it’s no wonder modern brewers love to debate their pros and cons. 

Commercial breweries have indeed moved away from decoction mashing. It’s not a very efficient or streamlined process, and producing a product in bulk is a challenge with a decoction mash technique.  

For home brewers, though, decoction mashing can provide benefits. It can create crystal-clear finished beer and an exceptional malty flavor, similar to what you find in traditional European lagers. And, with modern technology, like thermometers, you can use decoction techniques in a simplified form. 

So, let’s dig into this time-tested technique. Below we discuss decoction mashing thoroughly, covering what it is, where it came from, and how you can do it at home. 

What Is Decoction Mashing? 

Decoction mashing is an all-grain brewing method for increasing the mash-in temperature in incremental steps. Sometimes referred to as a step-brewing technique, it’s both traditional and intense. However, it’s one of the only tried and true ways to mimic classic flavors found in central European beers. 

Decoction mashing is a three-part process that generally looks like this: 

  1. Remove part of the mash from the mash tun
  2. Boil it in a separate container
  3. Return the hot boiled mash to the main mash, which has been holding at a constant temperature. 

This traditional technique was universal to brewing historically. Today, it’s become much more controversial, but we’ll get to that in a moment. 

First, let’s look at the history of decoction mashing techniques. It’ll help us better understand the purpose behind this time-consuming traditional method. And, it will help you decide if it’s worth the extra energy decoction mashing requires. 

History of Decoction Mashing 

Decoction Mashing

Historically, decoction mashing was necessary to brew delicious beer. There were two reasons for this:

  1. Decoction mashing allows for repeatable results without a thermometer.
  2. Decoction mashing creates efficient and delicious brews with under-modified malt. 

Humans have been brewing beer since at least 5,000 B.C. Thermometers, though, weren’t invented by Daniel Fahrenheit until 1709! That meant, for a very long time, humans had to use other means to monitor and control the temperature in their brews. 

In the absence of thermometers, you can reliably increase the temperature of your mash using boiling water. However, adding additional water dilutes the mash and increases its volume. In other words, it might run over the top of the tun, and the results won’t be very tasty. 

So, early brewers probably tried to remove liquid from their mash, heat it, and then add it back. Unfortunately, that creates problems too. Enzymes reside in the liquid portion of the mash, and enzymes are easily denatured at boiling temperatures, rendering them ineffective. 

Though early brewers almost certainly had no clue what an enzyme was, they would have quickly discovered removing, boiling, and adding back the mash water alone doesn’t work. Without enzymatic activity, starches can’t convert to sugar, which means there’s nothing for the yeast to feast on. So, you can kiss fermentation goodbye and say hello to malted grain tea, which is pretty gross, in our opinion. 

It’s likely that early brewers switched tactics and began to follow a decoction mashing method similar to what we might use today. However, instead of pulling liquid decoctions, they switched to pulling out the mash solids with just a little liquid. 

They would boil the grains separately and then add them back to the mash, thereby raising the mash’s temperature in a reliable and repeatable way, without destroying enzymes. 

Doing this had another benefit. Malted barley at the time was under-modified in general. Boiling the grains softens them further by bursting the starch’s cell walls. With the cell walls out of the way, the enzymes can easily get to the starch within. The result is a stronger beer with the same sweet maltiness, which early brewers almost certainly appreciated. 

Decoction Mashing Today: Pros and Cons

Today, we have thermometers and fully modified malts. So, is decoction mashing worth the extra time and effort it takes? 

Well, it depends on who you ask. 

Modern Fans of Decoction Mashing 

Throughout Germany and the U.K., especially, you’ll find many fans of decoction mashing. It’s not because they’re Luddites who refuse to use thermometers. And it’s not because malts are lower quality on the other side of the pond. 

Modern fans of decoction mashing do it because of the flavor it imparts. When you pull grains from the mash tun and heat them to high temperatures, you can induce the Maillard reaction. 

If you like to bake bread or grill meats, you may have heard of the Maillard reaction before. It’s really a series of browning reactions that create malty, toasty flavors, and deeper color. It’s responsible for the crust on your steak as well as on your sourdough loaf. It makes food taste better, and it does the same for beer. 

Proponents of decoction mashing also claim that the process creates superior foam in your final brew. Foam quality and head retention have to do with the proteins in your decoction wort, though. And, decoction mashing techniques vary. 

If you’re using under-modified or moderately modified malts, the protein rest that decoction brewing calls for will break proteins up and provide better head retention. With fully modified malts, larger proteins will break down, and the resulting foam will be unstable. 

So, while decoction brewing certainly affects the foam of your beer, it’s not always for the best. 

What The Haters Have To Say

Many modern breweries and homebrewers have ditched the decoction mash method. They say it’s simply not necessary with today’s equipment. Well-modified malts are readily available, and everyone has access to a thermometer. 

As they point out, an infusion method is far easier, and you’ll get similar results. In addition, adding a little melanoidin malt to your mash will create additional flavors similar to decoction mash methods. 

However, it’s not exactly the same. If you’re a true fan of traditional brewing flavors, the kind you find in real-deal pilsners, Bochs, and hefeweizens, the decoction method is the only surefire way to get there. 

Before You Begin 

If you want to try a decoction mash method, there are a few things to know before you begin. Let’s go over them. 

What Equipment Do I Need For a Decoction Mash? 

Though decoction mash methods were developed without modern equipment, having a few standard pieces can help modern homebrewers. 

You can use a traditional 3-vessel set-up, brew-in-a-bag options, or even an all-in-one system with a decoction mash. On top of that, you’ll need:

  • A decoction kettle: A standard aluminum or stainless steel kettle will work. This is for boiling the decoction, nothing more. So it doesn’t need anything special, like a false bottom or ball valve. Ideally, the volume will be about half of your mash tun.
  • A heat source: This is to boil your decoction, and any heat source will do. Propane, electric, and induction stove-tops all work well. 
  • Scoop or Sieve: This is to transfer the decoction to the kettle. 
  • Heat resistant jug: This is also to transfer the decoction. 
  • Thermometer: It’s true that brewers developed traditional decoction methods before thermometers were around, but make it easy on yourself. A thermometer helps! 

Decoction Volume Calculations

Traditionally, each decoction uses the thickest 1/3rd of the mash. That rule of the thumb came from ancient brewers who weren’t making advanced calculations for their brews. However, it still works well with a 3-vessel all-grain mash system. 

However, homebrewers today use a wide range of equipment, including brew-in-a-bag pieces. So, to be more specific, you can calculate decoction volume using the following formula: 

Decoction Volume = 

Total Mash Volume * (Target Temperature – Starting Temperature) / (Mash Boil Temperature – Starting Temperature)

Make sure the volume of your decoction kettle can handle at least 25% more than your calculated decoction volume to accommodate space for boiling and stirring. 

Types of Decoction Mashing 

If you’re going to use a decoction mash, there are a few ways to go about it. The most traditional technique is known as a triple decoction. Unfortunately, it’s lengthy and rarely used today, even by fans of decoction mashing.

However, understanding it makes practicing other, more modern decoction mash techniques that much easier. So we’ll detail the process in full below, and then we’ll run through double and single decoction mash techniques. 

Triple Decoction

A triple decoction has four mash rests to be aware of: 

  • Acid rest: lowers mash pH and prevents gumminess. Also called the low-temperature rest
  • Protein rest: breaks down proteins for better clarity. 
  • Saccharification rest: adds malty complexity, color, and sweetness. 
  • Mash-out: stops enzyme action and preserves fermentable sugars. 

Traditionally, these rests are long, but many modern brewers who practice triple decoction shorten the rests to account for fully modified malts. 

Ideally, you would use under-modified malts that can withstand the longer rests without breaking down. Some maltsters sell under-modified malts precisely for this reason. 

It’s also ideal to have a brewing partner with this technique. Each time you pull a decoction and bring it to a boil, you’ll need to stir it regularly. It can be tricky to mix your decoction while keeping an eye on your main mash. 

Step One: Mash In 

To start a triple decoction mash, heat your strike water to around 99℉. Remember, brewers developed the triple decoction method before the advent of thermometers, so most of the temperatures are easily identifiable. In this case, the strike water temperature should be just above body temperature; it will feel neither hot nor cold if you were to run your hand through it. 

For light beers, you’ll want 2.3 – 2.6 quarts of water per pound of grist or grain. For dark beers, you need less. 1.4 to 1.9 quarts per pound of grain will do the trick. 

Step Two: Acid Rest 

At around 99℉, the enzyme phytase activates, which will lower the pH of your mash. Allow the mash to rest here for about 20 minutes. 

Step Three: Pulling and Heating the First Decoction

To pull the first decoction, you scoop out the thickest portion of the mash, aiming for about 1/3rd of the total mash volume.

If you’d like to use a more exact measurement, you can use the decoction volume equation we provided earlier. The target mash temperature will be 122℉.

Once you pull your decoction, you’ll heat it in a separate pot (your decoction kettle) to around 150℉. Then, let it rest for 15-20 minutes. The rest allows the starch conversion before you destroy the enzymes with boiling water. 

Be careful not to scorch the grains as you heat them. We suggest heating slowly and stirring regularly! 

Step Four: Boil the First Decoction 

After resting the decoction, it’s time to turn up the heat and

beer from bread

bring the decoction up to boiling. 

For light beers, the decoction boil time is 5-15 minutes. For darker-colored beers, you’ll need to boil them for 30 minutes or more. The longer you boil, the more color and caramel flavors you’ll create. 

Step Five: Return the Decoction Mash for the Protein Rest

After the decoction is done boiling, you’ll return it to the main mash. The goal is to raise the entire temperature of the mash to about 122℉. 

Use a heat-proof jug and a sieve to return the decoction to the mash slowly. Remember, the decoction will be hot, so be cautious and don’t rush. 

Once you reach the target mash rest temperature of 122℉, stop adding the decoction and allow the mash to rest for 15-30 minutes. 

If your mash reaches temperature before adding all of the decoction, chill the remaining decoction separately to 122℉ and then add it back to the mash. 

Step Six: Pull the Second Decoction, Boil, and Perform the Saccharification Rest 

At this point, you repeat the decoction process (steps three, four, and five). 

If you’re using the decoction volume calculation, your target temperature will increase to 145℉. In other words, once you add the second decoction back to the main mash, the temperature should be 145℉. 

Resting the mash at this temperature will create the rich malt flavor you’re looking for as the process converts starch to sugar. You can rest the mash for as little as twenty minutes here, but traditional methods called for resting the mash for closer to an hour. If you’re using under modified malts as we suggested, the longer rest will be beneficial. 

Step Seven: Pull the Third Decoction, Boil, and Perform Mash Out

Repeat decoction steps three, four, and five again. This time the target mash-out temperature is 170℉. 

Then complete the mash-out rest; usually, 10-15 minutes is sufficient. 

Step Eight: Sparge and Finish the Brew 

You can batch sparge, fly sparge, or no sparge. That part is entirely up to you. Then collect the total volume of wort in your brew kettle and finish, just as you would any other brew.  

Single and Double Decoctions 

With fully or moderately modified malts, homebrewers who want to use a decoction mash often shorten the process to double or single decoction. 

The double decoction mash omits the acid rest at the beginning. Instead, you start with the protein rest. Then you’d pull the two remaining decoctions to reach the appropriate saccharification temperature and mash out. 

Single decoction begins with the saccharification rest. You’ll pull one decoction to reach mash-out temperatures. 

Regardless of whether you use triple, double, or single decoction, there are several variations you can make as a brewer to suit your preferred malts. Duration of rests, the heating rate, and the number of rests are all modifiable. 

In the next section, we’ll focus on a much more practical process for a decoction mash. While the above method worked and was undoubtedly ideal for historical brewers, the next method we feature is better for modern-day malts, using standard equipment. 

How To Use a Decoction Mash In Your Next Homebrew 

If you want to develop traditional distinctive flavors in your beer, using a decoction mash is crucial. That’s especially true if you’re brewing a Bavarian or German-style beer. However, you don’t need triple decoction to get there. 

Below, we discuss the Hochkurz technique. Hochkurz is German for “high and short.” The mash begins well above the standard protein rest temperature, and it requires less time there. So, it’s literally a high and short method for brewing beer. 

Hochkurz Technique

The Hochkurz technique is a double decoction method that uses the same process of decocting the thickest part of the mash, heating it, and adding it back in. It looks like this: 

  • First rest at 144℉ for 35 to 45 minutes
  • Second rest at 160℉ for 30 to 45 minutes
  • Mash out at 170℉ for 10-15 minutes

The Hochkurz technique relies on specific temperatures that you need a thermometer to find. Each temperature encourages a particular enzyme. 

The first rest is sometimes called the beta-amylase rest because it encourages the beta-amylase to work quickly. Beta amylase is responsible for cleaving maltose from complex molecule chains, and maltose is the primary sugar for fermentation. So, the first rest is vitally important. 

The second rest encourages alpha-amylase activity. This enzyme also degrades sugar molecules into digestible components, encouraging good fermentation later on. 

Technically speaking, you don’t even need decoction to use the Hochkurz technique. Hot water additions and direct heat methods will also work. 

However, adding extra water means thinning out your mash, which isn’t necessarily ideal. And, direct heat methods may not work with your equipment. So, a decoction is a popular choice for using the Hochkurz technique. 

You do need well-modified malts to make this technique work. Attempting it with under-modified malts will yield poor results because it’s a much shorter method. 

A triple decoction mash process can take between 3-1/2 and 5 hours; generally, the Hochkurz technique takes about two hours. Well-modified malts don’t need the extra rest to convert their starches into sugars, but under-modified malts do. 

Frequently Asked Questions

Before we close, let’s go over a few common decoction mash questions. 

What Styles Benefit Most From a Decoction Mash? 

As we mentioned above, a decoction mash is common for central European beer styles. Continental Lagers like Bochs and hefeweizens do incredibly well with a decoction mash method. 

Pilsners, helles, and dubels are excellent candidates too. A decoction mash will increase their maltiness and provide a better mouthfeel. 

Can I Use My Boil Kettle as a Decoction Kettle?  

Yes. Many homebrewers use their boil kettle as a decoction kettle, but that comes with a significant downside. You’ll have to thoroughly clean out the grain before sparging, which can be a tiresome task. It’s easier to have a separate kettle on hand. 

If I Have Well Modified Malts, Is There Any Benefit to a Decoction Mash? 

With well-modified malts, like an American 2-row malt, a decoction mash isn’t necessary, and in some cases, it may be detrimental. However, many find benefits in using single or double decoction methods with well-modified malts. 

A single, or sometimes double, decoction can add malty flavors, caramel colors, and better mouthfeel even with well-modified malts. The trick is not to rest the mash too long. Traditional resting times suggested in triple decoction methods will hurt the quality of well-modified malts. 

Final Thoughts 

Traditionally, decoction brewing was a beast of a technique. It took a day of babysitting your mash, and most of us don’t have time for that. 

Luckily, modern technology allows you to shorten the process without sacrificing flavor and quality. By using well-modified malts with a single or double decoction, you can increase the sweet, caramel flavor and color of your brews. And we think that’s a very cool thing!  

After all, homebrewing is all about innovation and discovery. Using a decoction mash is one more way to expand the creative potential of your homebrewing and create a tasty beer. It allows you to experiment with malty flavors and caramel colors, creating brews similar to traditional Bochs and pilsners. We call that a win!