Understanding All-Grain and Partial-Mash Brewing

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This page gives an insight into aspects of all-grain and partial mash brewing, providing information on what sets it apart and what is involved in each step. We strongly advise that you read it thoroughly before getting stuck into all-grain and partial-mash brewing.

All-grain and partial-mash brewing gives the home-brewer far more control over the final brew. Extract brewers rely on the maltster to convert and extract fermentables from the grain for them. All-grain and partial-mash brewers reclaim this process, giving themselves total control over the final product. In addition, the extra processes involved allow for a whole range of ingredients to be used which are not utilised in extract brewing. While it is true that the main base malts and styles can be found in extracts, lots of specialty malts and adjuncts cannot.

The method of transforming the raw material to fermentable sugar is known as mashing and in itself is a pretty straightforward process. The mash comprises of steeping crushed grain in hot water, this causes the starches in the grain to start to gelatinize. As a result, the starches become vulnerable to attack from enzymes, this breaks down the starches into sugars. The released sugars merge with the water to form wort. The grain is then extracted from the wort, and the wort continues the brewing process in a similar way to extract brewing. The main difference between all-grain and partial-mash brewing is that in partial-mash brewing, the mashing procedure is used to supplement extract brewing, whereas in all-grain brewing, extract is not used at all.

Propane Burner

Because all-grain brewing requires a bigger pot and a greater volume of liquid, a propane burner is commonly used as a heat source.

Mash Tun

The main apparatus required to conduct a mash is a mash tun. Lots of brewers combine the mash tun with a lauter tun, which is used to extract the wort from the grain. When combined, it is referred to as an MLT. A common form is a picnic cooler with a spigot at the bottom. The cooler maintains the mash temperature which is vital for good starch conversion. The wort is removed from the cooler through the spigot.

To prevent the grain from flowing out of the cooler along with the wort, a manifold is sometimes positioned at the bottom of the cooler which allows the water to flow equally through the grain. Alternatively, a screen or braided steel is used. The aim of both techniques is to use the grain as a natural filter, removing particles from the wort.

If you do not have a mash tun, there are a number of work arounds. One popular method is to place the grain into a large nylon bag, which are available at many homebrew shops. The bag can be added into the kettle or used as a strainer inside a picnic cooler. This method is known as “Brew in a Bag” and is very popular, it is particularly versatile as it can be used with or without sparging, or in partial-mash or small batches of all-grain brewing


Before it can be used, the malted barley must be ground or crushed. Plenty of home-brew stores will pre-crush the grains for you, or allow you access to their mill for you to crush it yourself. This is a great way to get to grips with mashing, as it avoids the necessity of purchasing your own mill.

Ready to Mill Grain

The degree and kind of crush is very important to the mash process. The starch must be broken up in order to make it accessible to the mash—the smaller the particles, the larger the surface area and hence the easier it is to convert them into sugars. But if it is too fine, you will get a consistency similar to glue when it is added to water. Making the lautering process (extracting the wort from the grain) much harder. Another important factor to keep in mind is the husk of the grain, as this is what will form the filter bed, allowing extraction of the wort. Preferably, the husk should retain its integrity and be separated from the grain. If the husks are ripped into small pieces they will not form an effective filter and this will affect flavours later.

Doing the crushing yourself provides another level of control. The capability to extract the sugars from the grain is relies on how well the grains have been crushed and as they say, if you want something doing well, do it yourself! A major part of making great beer is being able to control as many processes as you can and do so repeatedly.

Milled Grain

There are two main kinds of mills that are used in homebrewing. The Corona-style mill is relatively inexpensive and is very effective. The mill functions by pushing the grain through a set of rotating plates. As they proceed, the plates crush and tear the grains apart. There are two disadvantages to this type of mill, firstly, they are difficult to adjust with any kind of precision and they need to be tuned often. As such, they are generally less consistent. The second issue is that they tend to rip the grain husks apart, which, as mentioned earlier, can negatively affect the natural filter effect, which can add unwanted flavours.

Corona Mill

A corona mill

The second type of widely available mill is the roller mill. Roller mills push the grain between two (or more) rollers, producing in a true crush. The grain is successfully separated from the husk with a small amount of tearing. It is simple to adjust them and is much more consistent than a corona-style mill. The main disadvantage is the price, which can be easily two or three times as much as a corona-style mill.

Roller Mill

The rollers on this roller mill provide fine tuning over the crush.


The extract potential of grain is a combination of the amount of starch in the grain, and your ability to transform those starches to sugars, which is a measure of your efficiency. As a homebrewer, 100 percent efficiency is unobtainable, as this can only be achieved in a laboratory, but your efficiency can be contrasted against the ideal to determine how efficient your process is in transforming starches to sugars and finding those sugars in the wort. Increased efficiency can be achieved by decreasing the particle size of the grain – making it finer. The problem with this is that if the grain becomes too fine, when the wort is extracted, it stops acting as a filter and blocks the entire operation which makes it extremely difficult to drain the wort effectively.


The Mash

In all-grain and partial-mash brewing, there are two steps which are critical to the outcome of the beer; the fermentation and the mash. Conducting a mash is what separates this kind of brewing from extract brewing. During the mash, the starches from the grain are transformed into sugars by enzymes which are located in the barley. A brewer’s job is to provide conditions which are optimal for this conversion, factors such as wort thickness, temperature and amount of enzymes present need to be adjusted.

Once you have allocated a mash tun and have your grains crushed and ready to go, it is time to begin the mash. The first step is to bring your strike water to the appropriate temperature. The strike water is the water that will be mixed with the grain at the start of the mash, but this raises two important questions—how much water and at what temperature?

The Science of the Mash

It is definitely possible to brew outstanding beer and not understand what’s taking place during the mash. However, having a better understanding of what is taking place will provide you with an insight on what you need to change to tweak your beer to your desires. The goal of the mash is to transform the starches, located within the kernel of the grain into sugars, which is consumed by the yeast during fermentation to produce alcohol.

The bulk of the barley kernel consists of starch. Starch molecules are long chains of glucose, a simple sugar. By themselves, starches are not fermentable; as such they must be converted into the sugars which they are made up of. Through the malting process a number of enzymes are secreted which, under certain circumstances, will transform the starches into shorter glucose chains. These shorter chains contain molecules such as maltose, a particularly fermentable sugar which is made up of two glucose molecules, and maltotriose, which is made up of three glucose molecules. Dextrins are molecules which are made up of four or more glucose molecules, these are unfermentable. However they provide body and mouthfeel to the beer.

There are two main enzymes which are responsible for this transformation and both become active during the mash; alpha-amylase and beta-amylase. Alpha-amylase breaks down long starch molecules by attacking the middle of them. Beta-amylase is an enzyme which attacks the ends of the starch molecules, both release sugars. As beta-amylase operates at the ends of the glucose chain, it’s activity is increased by alpha-amylase, which essentially creates more ends for beta-amylase to get to work at.

The enzymes must be steeped within a particular temperature range for them to become activated. Each enzyme has a different optimal temperature range, but there is enough overlap within these different ranges to find something that works. Alpha-amylase has an optimal temperature range between 149 and 153 degrees Fahrenheit. It will continue to work at higher temperatures, up to a point, where it will completely stop working. Beta-amylase works best between 126 and 146 degrees Fahrenheit.

In general, both enzymes will operate at an acceptable rate together between 145 and 158 degrees Fahrenheit. As such, this is the temperature range where most mashes are conducted. However, adjusting the temperature to the higher or lower ends of this range will create different flavours. Due to the way that the enzymes function, higher mash temperatures will produce beer with greater body as a higher proportion of unfermentable dextrins are produced. If lower temperatures are used, a higher proportion of fermentable sugars are produced, the result is a beer with lighter body and alcohol content.

When trying to brew a beer with greater body, a mash out is often done, this involves raising the temperature of the wort to more than 170 degrees Fahrenheit. At these temperatures, the enzymes completely cease to work, preventing dextrins from being broken down. It also makes it easier to drain the wort through the grain bed, in the lautering phase which follows.


The volume of water that you are going to need depends on the amount of grain which you will be adding to the mash. As a general rule, you want to add around 1.4 litres of water per ½ Kg. Clearly there will be limits to the amount of grain and water than can physically fit into one pot. If you are using a large amount of grain, you may have to use less water.

Mashes are conducted in a temperature range of 145 and 158 degrees Fahrenheit, with the majority of recipes using a mash between 150 and 158 degrees Fahrenheit. For reasons mentioned earlier, a higher the temperature produces more dextrins, leading to a beer with more body and mouthfeel. A lower temperature, produces a lighter body and higher alcohol content.

Mash Time

The length of the mash – which is essentially the time required for the enzymes to transform the starches into sugars – depends on the temperature of the mash. A mash which uses the high end of the temperature spectrum can take as little as 15 minutes, while a mash at 145 degrees Fahrenheit can take up to an hour and half. So how do you know when the mash is finished? The simplest option is to only mash for one hour. In most cases, this is long enough and is said to be a good compromise for the majority of beers. The second option is to do a starch test, a simple test which involves removing a small sample of wort from the mash tun and adding a drop of iodine to it. If the wort changes to a black/blue colour, the mash is not finished; if there is no observable colour change, you’re finished. When extracting a sample of wort, you only want a few drops, ensure that there is no grain either, as this will cause a false positive.

Insulated Mash Tun

To keep the mash at a constant temperature, some form of insulation is needed. In this image, insulation has been wrapped around the mash tun for the duration of the mash.


Once the mash has finished, the spent grain must be separated from the wort. This is process is known as lautering. For many homebrewers, the mash tun also functions as a lauter tun through a false bottom, manifold, or screen located at the bottom of the mash tun. This allows the brewer to extract the grain as the wort drains from of the vessel.

Mash Tun with False Bottom

This mash tun has a false bottom which assists in lautering.


While the aim of this process is to separate out the wort from the grain, the spent grain is utilised as a natural filter. As the wort flows out of the lauter tun it moves downwards and through the grain bed, this acts as a filter to remove particulate matter and allows the wort to be extracted cleanly. The size of the crush, which was done before the mash, is important here. If the grain was ground to the consistency of flour and the husks were torn to shreds, the grain will not function as an effective filter bed. Instead, the will clog the filter and make it extremely difficult to extract the wort.

Grainy Wort

Prior to filtration, the wort is full of grain.

As mentioned earlier, there is an exchange between being able to use the husks as an effective filter bed, and crushing the grain finer in order to increase the efficiency of sugar extraction from the grain. To increase the crush, and thus maximum sugars, while also having a suitable filter bed, some brewers insert rice hulls to their mash. This increases the amount of material which can act as a filter and has no impact on the taste of the final brew.

When the wort is first drained from the lauter tun, the first few litres should be re-added to the lauter tun in order to be filtered again. This is because the first few litres of wort which is extracted will be cloudy as the grain bed takes a while to act as an efficient. Once the grain bed is functioning correctly, the wort will appear clear and does not need to be re-filtered through.

The method which is used to extract the wort depends on what method of sparging is used.


Sparging is the practice of rinsing the grains to extract excess sugars. Once the mash has finished, the wort is sugary and sticky. As such it will adhere to the grains but can be removed by rinishing with hot water. Homebrewers use two main methods of sparging—fly sparging and batch sparging. Both are capable of producing excellent beers and using one over another is usually just a personal preference.

Fly Sparging

Fly sparging is the type of sparging which is used in the majority of commercial breweries; it is also the traditional method for homebrewing. Also referred to as continuous sparging, fly sparging involves having the wort drawn slowly from the grain bed. As the level of the wort decreases in the mash tun, hot water (around 170 degrees Fahrenheit), known as sparge water, replaces the lost wort, at an equal rate. The top of the grain bed is must not run dry, and it is important that the level of sparge water is kept only slightly over the top of the grain bed. It is also vital that the grain bed is not disturbed, and while not required, most homebrewers use a sprinkler head to gently replace the wort with sparge water. This sprinkler head is commonly gravity fed from a hot liquor tank.

Fly sparging is the number one choice for commercial breweries as it permits greater extract efficiency, and in a well-designed fly sparge system, homebrewers can also reach very good extract efficiencies. Another advantage of fly sparging is that less water is required compared to batch sparging. The volume of sparge water that needs to be used depends on the amount of water used in the mash. If you’re making a beer which has a very large grain bill, it will require more water in the mash, compared to a beer with a smaller grain bill. Because there are limits to the volume of liquid that any system can hold, the more wort that is drawn from the mash, the less sparge water that can be added.

Fly Sparge

Lots of mash tuns are available to purchase which come with false bottoms, these allow for even drainage when fly sparging.

Nevertheless, there are disadvantages to fly sparging. As the end of the sparge approaches, the pH of the water increases and needs to be monitored. Should the pH rise above 6, tannins will be obtained from the grain husks, this causes an undesirable astringency.

Another disadvantage associated with fly sparging is the challenge of ensuring that the sparge water is running evenly through the grain bed. If the wort/sparge water is flowing too fast, it is said to channel through, instead of gently diffusing through the grain bed. If channeling takes place, only the zones of the grain bed which have sparge water running through them will have their sugars fully extracted, hence lowering your extract efficiency. The manifold positioned at the bottom of the MLT is used to draw wort from numerous areas in order to avoid channeling.

Another further disadvantage of fly sparging concerns drawing off the wort off too quickly and  so compacting the grain bed. It is important that the grain bed stays loose in order for the sparge water to gently run through it. If the grain bed packs down, it will cause the sparge water to again no longer flow evenly through, causing channelling and again decreasing efficiency. If the grain bed compacts too much, the MLT can become clogged, and no more sparge water will flow from the MLT.

Batch Sparging

Batch sparging involves allowing all of the wort to first drain from the MLT, prior to the addition of any sparge water. Once the wort has all been extracted, the MLT is filled with sparge water and the grain bed is disrupted. Once the grain bed has been disrupted, commonly through stirring, the sparge water is fully drained from the MLT.

This method is not popular in commercial breweries as it is said to have a lower extract yield compared to a well conducted fly sparge. However, for a homebrewer this method is simple, and while the yield may be slightly lesser than fly sparging, it can be countered by adding a small amount of extra grain. In a large scale, commercial brewery, the extra grain which would be required to counter the lower efficiency would be a huge amount. However, in a standard 5-gallon batch brewed by a lowly homebrewer, the cost is negligible.

If the difference between extract potentials was the only worry, the main question would be, by how much does it differ? Some studies have been conducted at most, a difference of .004 gravity points was observed and many studies claim to have no difference at all. While these experiments are not definitive, it does show that the extra efficiency obtained by fly sparging is limited at best.

The process of batch sparging is much simpler too, instead of a manifold positioned at the bottom of the MLT, a simple screen is used, simply to prevent the grain from leaving along with the wort/spage water. In addition, because the mash tun is totally drained, channeling is less of a concern.

Batch Sparge

This MLT has a piece of screening in order to stop the grain from clogging up the pipe. This is ideal for batch sparging.

There is one more alternative to batch and fly sparging: no-sparge. This is exactly what is sounds like, sparging is skipped altogether. A very thin mash is required, usually with around 3.5 litres of water per 0.5 kg. The wort is just drained from the grain bed or, like in the Brew in a Bag method, the grains are raised out of the wort. As you can expect, the no-sparge method has a lower extract efficiency compared to fly sparging and batch sparging. Nevertheless, the technique is straightforward and requires no additional equipment.

Brew in a Bag (BIAB)

The Brew in a Bag method is a type of brewing which was created by homebrewers in Australia. It is basically a no-sparge method of brewing which is particularly simple to conduct. Essentially, the mash is achieved by inserting the grain into a bag which can later be removed. No sparging is done. As such is requires very little specialised equipment and is a great way for extract brewers to start the transition into all-grain or partial-mash brewing.

Supposing you already have a large pot (around 10 gallons for a 5-gallon brew), the extra piece of equipment required is a large nylon or polyester bag. Lots of homebrewers fashion their own bags using a fabric known as Swiss voile which can be found in most fabric shops. The bag needs to be large enough so it can totally line your pot and have lots of excess at the top so that you can grab it bag and lift it out once the mash has finished.

The grains are crushed very fine and added to the bag. In this technique, the mash is very thing, with around 3.5 litres of water per 0.5 kg of grain. Once the water has reached temperature, the bag is added to the pot and the pot, covered and insulated. Like other methods, the mash is conducted for roughly an hour. You can do a mash out, but it not required. Once the mash has finished, the bag is raised out and allowed to drain back into the pot. Normally, BIAB is a no-sparge method of brewing. When the majority of the wort has been drained from the bag, give it a squeeze to get as much out as possible.

From here on, simply follow the normal method of bringing the wort to the boil, adding your hop additions, chilling, pitching and fermenting.

The Boil

When extract brewing, the main reason for an extended boil is to guarantee correct hop utilization in order to achieve proper bittering. There are lots other advantages to a full boil; however, these have already been achieved by the maltster through the production of malt extracts. When brewing all-grain or partial-mash, you need to perform the boil yourself.

The Boil

The boil normally lasts between one and one and a half hours, and provides numerous benefits to the brewer. Firstly, it has an effect on hop utilization, the bitter flavour presented by hops comes from their alpha acids, this number is often on the package which the hops come in. Alpha acids are not directly soluble in water, as such they must be isomerized first, and this involves slightly altering their molecular structure in order to make them more soluble in water. The amount of isomerization which takes place is dependent on time, the longer the boil continues, the more bittering compounds are dissolved into the wort. This is why bittering hops are added at the beginning of the boil.

The boil also provides protein coagulation. Performing a good rolling boil will help in the coagulation of proteins which are then removed from the wort. This is what forms on the top of the wort when it first begins to boil. Removal of these materials is vital in order to produce a clean and clear beer. In a good boil, the wort looks as though it is folding over on itself. As the boil continues, proteins join together and ultimately fall out of suspension. When the boil first starts, you need to be wary of boilovers. This occurs when a large amount of foam forms on the surface of the wort, due to this protein coagulation, and spills over. This generally causes a horrible, sticky mess and is something you want to avoid. The wort can be briefly removing the wort from the heat, or stirring it to break up the foam can prevent boilovers.

During the boil, volatile compounds which form during the earlier steps are removed through evaporation. Dimethyl sulfide (DMS) is a molecule which is produced in hot wort, at high levels it gives the beer a cooked corn flavour. During the boil, DMS evaporates, leaving the wort and therefore giving a cleaner flavour. Because of compounds like DMS, the wort should never be covered during the boil, as this will prevent the evaporation of volatile compounds, causing off-flavours.

Lastly, a good rolling boil assists in the expansion of flavour and colour compounds within the wort. Maillard reactions are browning reactions, the same which takes place when you make toast. Due to the heat involved in the boil, Maillard reactions take place within the wort. The flavours which are produced from these reactions are responsible for the richness of the malt flavour, apparent in some darker beers.


Once the boil has finished, the wort needs to be chilled as fast as possible to the temperature that you’re going to pitch the yeast at. This is done using a wort chiller or an ice bath. Like the boil, prompt cooling of the wort results in protein coagulation, which increases clarity.


In addition to this, chilling the beer promptly slows the evaporation of volatile compounds. The flavour and aroma characteristics released by hops which are added at the end of the boil would be evaporated off if they were included at the beginning of the boil. Therefore chilling the wort prevents the evaporation of these volatiles, preserving both the hop aroma and flavour.

Lastly, the wort needs to be reduced down to the yeast-pitching temperature, pitching the yeast at a temperature which is too high leads to the development of off-flavours. When the yeast is first added to the wort it undergoes a growth phase before fermentation takes place. In the growth phase, precursors of the adult yeast cells are produced, these are later removed by the adult yeast cells. If the temperature is too high when the yeast is pitched, these precursors explode in number and are not removed, causing the development of off-flavours.

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