Beer Mash: Complete Guide on how to do It!

For those who are just starting out in the world of homebrewing, the word “Mashing” may sound familiar. But what is it really and how is it done?

In this article, I am going to tell you what mashing really is, the different types of mashing there are, how to do it effectively, the ideal temperature at which it should be done, the different elements you will need to do it, and much more!

So, without further ado, let’s get started!

The Mash consists of mixing hot dechlorinated water with the ground grain (generally in a 3:1 ratio) and keeping it at a temperature of between 62 and 72 degrees Celsius, which after 60 minutes results in the wort that has all of the sugars necessary for fermentation to produce beer.

What is the Mash?

The mash is the process in which, from malt and water, we obtain wort and grain leftovers, and this wort is composed of water (approximately 85%, depending on the concentration) and extract.

The extract is, essentially, all the substances dissolved by the water, mostly coming from the malt (and adjuncts in case they have been added) through the mashing process using adequate mashing times and temperatures for the correct enzymatic action to take place.

This extract is the substrate on which the yeast will act on during the fermentation stage and is composed of fermentable sugars, Alpha Amino Nitrogen (AAN), vitamins, and minerals.

Types of Mash: Basic, Step Mashing, Decoction, and Partial Mash

There are several mashing methods out there, but nowadays, the simplest and most widely used one is the basic/simple mash, which consists of making a mash with the total amount of grain and a volume of water (hot and dechlorinated) with a water-to-grain ratio of between 2:1 and 4:1, depending on the style of beer you are going for.

Once this mix is done, it is left to “mash” at a fixed temperature for approximately 20 minutes and then heated up to a different temperature and left there to sit for another 40 minutes.

Another widely used method is step mashing which consists of starting the mash at a lower temperature and gradually increasing it until a target temperature is reached in order to allow for the optimum enzymatic action since they act differently depending on the temperature.

On the other hand, the decoction technique consists of taking a portion of the mash (the thickest and most concentrated one), boiling it, and then mixing it together again with the mash which is automatically heated up when mixed.

Finally, a method that is not so widely used is the partial mash which consists of infusing all the grain with water at a single temperature, usually for around an hour but with a much smaller amount of grain, which is then replaced by a malt extract that is responsible for adding the rest of the fermentable sugars.

Let us look at each one in more detail:

Simple Mash

Assuming that you will perform a classic mash (3:1 water-to-grain ratio), you need to, for example, heat up 12 liters of water to 65°C and then incorporate little by little the 4 kg of ground malt stirring continuously so that no lumps are formed.

Once this part of the process is finished, you should be left with a mash at approximately 62°C, which you are going to let rest for 20 minutes stirring intermittently and controlling the temperature (it should be maintained at 62°C +-1). More on this later on.

Once this time has passed, the mash is heated up again, stirring so that it remains homogeneous until it reaches 72°C where it is left to rest for another 40 minutes, also stirring occasionally and making sure that the temperature doesn’t fluctuate.

Stepwise Mash

The stepwise mashing technique consists of starting the mash at about 40°C and raising the temperature by 10°C allowing for 25-minute breaks between each step until it finally reaches 80°C.

This method was used in the past to provide each enzyme with a certain amount of time at the optimum working temperature to extract all of the sugars from them.

Nowadays, it is not necessary to carry out this process to be able to extract all the sugars optimally since malts have been genetically modified.


Decoctions have the advantage of modifying a greater amount of insoluble components since they “burst” during the boil.

The disadvantages are the inactivation of enzymes during the boil, the stronger color obtained (due to the Maillard reactions at boiling temperature), the loss of a greater quantity of aromatic compounds, and, not least, the high energy costs.

Nowadays, with the use of well-modified malts, it is not necessary to carry out this type of technique except when brewing some special beers.

Partial Mash

A partial mash can be done with any of the techniques previously mentioned and by adding some malt extract. This method is quite usual when “Brewing in a bag”, but more on this in a second.

Essentially, using malt extract can help you skip many of the usual brewing steps, such as malting, mashing, filtering, etc., since the sugars don’t need to be extracted from the grain via some of these processes.

Brew in a Bag vs. regular mashing

The brew-in-a-bag method basically consists of putting all of the grain into a micro-perforated bag that allows water to enter but does not let solid matter out, such as the grains.

This bag is then used to mash right inside the kettle and allows you to simply lift up the bag once the mash is complete, making it especially easy for beginners since having a kettle with a false bottom isn’t something most brewers who are just getting started have access to.

Advantages of bag mashing

  • Saves space since you only need one pot.
  • Avoids possible clogging of valves and pumps
  • Easy to clean (all the grain stays inside the bag)
  • The bags are very cheap and easy to obtain.

Cons of bag mashing

  • Difficult to remove the bag due to its weight.
  • Generally, lower yields.
  • The bag can break or even burn if the flame is too high and the bag is touching the bottom of the kettle.
  • Over time, the bag absorbs some of the color of previous batches, which might affect the color of future ones.

Elements you Need for the Mash

The following is a list of all the elements necessary to carry out a classic mash:

  • Kettle with a false bottom, adequately insulated, and with an extraction valve (A regular kettle/large pot and a brew bag can be used instead).
  • Ground Grain.
  • Hot water with salt modification depending on the style.
  • Acid to modify the PH of the wort (the most used ones are citric and phosphoric)
  • A spoon or brewing paddle for stirring the mash.
  • Measuring instruments such as a refractometer and ph meter.

Guide on how to Mash

Now that you know all about the different types of mashing processes, it’s time to get into the nitty-gritty and show you step by step how to do a simple mash yourself.

Before getting started, however, and if you haven’t bought your grain pre-ground, you will need to grind it yourself, and this needs to be done in a very specific way: The grain needs to be uniformly crushed since you don’t want too much grain dust/flower (about 10% is recommended) and the same goes for the number of grain husks (10% is recommended for a good bed).

Step 1: Mash in

Preheat the water to the required temperature (generally around 62°C mark) and then you can proceed to add the malt and adjuncts while stirring using a spoon or a brewer’s paddle to prevent lumps from forming.

When stirring, do so relatively gently since you don’t want to incorporate too much oxygen at this stage.

Step 2: First rest

Once the temperature is stabilized at 62°C (heat up if necessary), it is left to rest for 20 minutes, stirring occasionally and checking that the temperature does not drop too much. In this step, the Beta-Amylase enzyme is the one that’s being allowed to act.

Step 3: Second rest

Here, the wort is heated up to about 72°C and left to rest for 40 minutes from the moment the temperature is reached.

Once the 40 minutes are up, it is recommended to perform an iodine test to confirm that the mash is actually finished, and if not, just let it sit for a few more minutes.

Step 4: Prior to Sparging

In this last step, to finish the mashing process, the mixture is brought slightly above 75°C to reduce the viscosity of our wort and stop the enzymatic action. Alternatively, you could simply pour in hot water until the entire mixture reaches the desired temperature.

Now that your mash is ready, you can proceed to sparging, boiling, etc.

How temperature affects the mash

The mash temperature is a crucial factor in obtaining the desired fermentation profile in terms of attenuation and residual sugars, and the optimum temperature range is between 62°C to 72°C.

If you mash close to the lower limit, the activity of the Beta-Amylase enzyme is promoted, which acts on the ends of the starch chains, generating a highly attenuated wort that will give us a dry, low-bodied beer.

On the other hand, if you mash at high temperatures (close to 70°C), this will facilitate the activity of the Alpha-Amylase, an enzyme whose job is to leave longer starch chains, resulting in a full-bodied beer with residual sweetness.

Ideal temperatures at which to Mash

This depends 100% on the style of beer you are brewing. For example, in blond beers with a dry finish such as American lager, Kolsch, Pilsner, etc., the optimum mashing temperature ranges between 62/64°C, while in darker, full-bodied styles, such as porter, Irish stout, etc., the optimum mash temperature should be around 68°C.

Most hoppy styles require a mash temperature that is in the middle of the two extremes (64/66°C) in order to produce a wort with good attenuation but which also leaves some residual sugars to support the amounts of hops that will be added later.

What are the rests?

Rests in the mash consist of raising the temperature to a certain point and then letting it sit for a specific amount of time. Each group of enzymes has an optimum temperature range in which they act in the best way on the different compounds of the wort. The most important ones to take into account are those that act on starch chains:

  • Alpha-Amylase: optimum temperature between 70°C and 75°C. A resting time of approximately 40 minutes should be given.
  • Beta-Amylase: works best between 60°C and 65°C with an optimal resting time of about 20 minutes.

How long should the grains be mashed?

The general rule of thumb says that a 60 minute mash is sufficient to complete starch conversion (saccharification).

To make absolutely certain that the mash has been completed successfully, you can do what is called the iodine test, which consists of taking a sample of wort and adding a few drops of iodine, and depending on the color, it will let you know if the mash is done or if you need to let it sit a while longer.

If it turns blue, you need to let it sit a while longer. Otherwise, the color won’t change at all.

Ideal Mash PH

The optimum pH of the mash is in the range of between 5.2 and 5.6, which offers the following advantages.

  • Better fermentation and greater attenuation
  • Better enzymatic activity (proteases, glucanases, phosphatases, amylases).
  • Decreased wort viscosity resulting in higher filtration speed.
  • Better protein breakdown and optimal trub separation.
  • Lower color worts are obtained
  • Faster diacetyl absorption during fermentation.
  • Improved flavor stability

How to raise or lower the pH of the mash

In brewing beer, the ideal pH levels used are generally below that of regular water, which is why acids are used to lower the pH of the wort, the most commonly used being citric and phosphoric acids.

It is extremely important to control the amounts you use because if you overdo it, there is no way to raise it back up again.

Although it is true that some minerals, such as calcium carbonate or bicarbonate, help to counteract the acidity of the wort, but they are only used in styles that include roasted malts such as a porter or a stout, but even so they are not useful for raising the PH ranges.

Is it convenient to mill the grains yourself or buy them milled?

It is definitely much better to grind the grain immediately before starting the mash (4 hours maximum) since when stored it becomes prone to contamination due to its greater absorption of moisture and oxygen.


The mash is the initial stage in the brewing block, so any mistake you make will be carried over to the finished beer. It is of utmost importance to respect the 3 main variables at this stage: temperature, PH, and mashing times.

Once this stage is finished, you will obtain what is called the “first wort”, which will be ready to be boiled and once that’s done, you can transfer this “final wort” into the fermenter.

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