The Mash Tun

mash tunThe most important elements of a mash tun are that it will hold heat well over a duration of a mash of around 60-90 minutes and that the grain can be seperated from the liquor easily, plus it being easy to clean.

There are numerous mash tuns available on the market. The picnic cool box with a manifold in the bottom connected to a tap on the outside to separate the grain and wort are probably the most common. The clear advantage of using an insulated box is the very fact that it’s insulated, with mash temperature being such an important part of the brewing process, you’ve got a product ready made to hold temperate. The manifold in the bottom comes in several variations such as a copper pipework system with holes drilled into the pipes to allow wort to flow through but not grain A stainless steel braided hose is another option. The main objective is whichever mash tun you use it needs to be able to separate the liquid from the grain.

Another type of mash tun would be a vessel with a false bottom an outlet is connected below the false bottom and only the wort can get past this false bottom. The simplest form of creating a mash tun like this is to drill hundreds of small holes (smaller than your crushed malt) in the bottom of a fermenting bin, this is in effect is the false bottom. This is then inserted into a fermenting bin with a tap at the bottom and the whole thing wrapped up in insulation or blanket so the mash tun can retain temperature. This method of building a mash tun is as basic and cheap as it gets but is still very effective and will produce beer just as good as any other mash tun.

The next variation for mash tuns are those that can be heated. So far the options would only really be good to do single infusion temperature mashes. If you wanted to perform a step mash then it would be difficult to raise the temperature in the mash up through the necessary increments. A vessel that can be heated would be able to perform a step mash and options for these often are constructed from stock pots with false bottoms that can be heated via a burner. In essence they perform the exact same function as the other mash tuns we talked about apart from the construction material.

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Mashing In

Mashing needn’t be thought of as hard. This is the most common conception of why people that I have spoken to anyway don’t make the step from extract to all-grain. If you have ever sat an wondered if your homebrew could be a little more complex and you want to know exactly what goes into your beer than Mashing is the way forward.

I am just going to lay out the basic steps required because in essence that’s all it is and there is no reason to make it more complicated in your head without having tried it.

OK here it is for a basic mash:

1. Crushed malted grains in the quantities of whatever recipe you are using are added to a mash tun with water that is heated to 72°C (or strike water temperature as discussed in a moment). You will need a thermometer for this as the temperature is the important part for the chemical processes that will happen in the mash. This process is called “doughing in” you need to make sure the grains are stirred thoroughly and all of it is soaked.


2. The temperature of the mash should have dropped to around 66-67°C by this addition of malt. If not add hot or cold water to bring to the correct temperature.


3. Leave the grains to mash. This is called a “rest” and is the longest part of the process and the part where you do nothing. You need to leave the mash to convert starches to sugars and perform other chemical process for around an hour and a half. You only really need to sporadically check the temperature hasn’t dropped below 63°C, if it has add boiling water. I don’t bother checking for around an hour into the mash as my mash tun is fairly well insulated.


4. Toward the end of the rest you need to be heating water (liquor in brewing terms) in preparation to sparge (run off the sugary wort and rinse the malt) which leads onto the next part of the brewing process.


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Calculating Strike Water Temperature For Mashing

When you first start all grain brewing or partial mash there are all sorts of thing that you need to start worrying about that you might not necessarily need to consider when you brew with kits or extract. Whilst you are a lot more involved and there are more variables to consider for example, water adjustment, water needed, mash volume and mash temperature just to name a couple of things that you need to include in your calculations before you even begin brewing.

When you come to brew your first batch this seems like a whole lot of hassle I know for me I was all over the place trying to figure out what was needed and when I should use it. When you get a few batches under your belt however these thing become second nature, just par for the course.

Strike Water Temperature

When I say strike temperature I am talking about the temperature of the water needed to achieve your desired mash temperature.

Say for example you want to hit a mash temperature of 67°C / 153°F we need to take into account what drop in temperature is going to occur when you add water to the mash tun and then add grain or if there is already water and grain in the tun. There is calculators and software available to calculate this for you, but why not give it a try by hand first.

Single Infusion Mash – Calculating Strike Water Temperature

The most common mash you are going to perform is a single infusion mash that only requires a rest at one temperature. For this type of mash you generally want the grain to sit between 65°C – 68°C (150°F – 155°F) for an hour for proper conversion.

With this in mind you’ll need to calculate the initial temperature we need to bring the strike water up to so that when we add it to the mash tun and add the grain it sits in the correct temperature range, below is the equation you need to use to find what this initial infusion temperature:

If you are using Fahrenheit, Pounds and Quarts then you’ll need to change the constant of 0.41 to 0.2

Strike Water Temperature Tw = (0.41 / R)(T2 – T1) + T2


  • Wa = The amount of infusion water to add
  • Wm = The total amount of water in the mash
  • T1 = The initial mash temperature (temperature of dry grain for initial infusion)
  • T2 = The target mash temperature
  • Tw = the actual temperature of the infusion water
  • G = The amount of grain in the mash


Mash Infusion Equation

To calculate the effect of an addition of water will have on a mash for example to bring the mash temperature up to hit mash out temperature or to perform a multi step mash we need to use the following equation:

Again you’ll need to substitute in 0.2 if you are using Lbs, Fahrenheit and Quarts


Wa = (T2-T1)(0.41G + Wm) / (Tw – T2)


An Example of Calulating Mash Temperature

Ok so with the above equations in mind let’s run through an actual calculation. Let’s say we are brewing a beer where we want the mash to sit at 67°C (152°F) for 60 minutes and then bring up the mash temperature to 74°C (165°F) to mash out. The temperature of our grain is 18°C

Using the initial infusion equation – Strike Water Temperature Tw = (0.41 / R)(T2 – T1) + T2 we would get the following.


(0.41 / 2.5) x (67-18) + 67 = 75°C


So we would need to heat our initial strike water to 75°C to hit our desired mash temperature of 67°C.

Calculating the addition required to raise the temp to mash out

We would then need to calculate how much of an addition of water is needed to hit the mash out temperature of 74°C. We will also assume the mash has cooled a few degrees to 65°C, our grain bill is 4kg and initial mash liquor is 10 litres. If we add recently boiled water that has cooled to 95°C we will need to use the following equation – Wa = (T2-T1)(0.41G + Wm) / (Tw – T2) achieving the following


(75 – 65) x (1.64 + 10) / (95 – 75) = 5.82 litres


So we would add 5.83 litres of 95°C water to take the mash from 65°C to 75°C.

Bear in mind there is software out there that will do all of this for you, but like a lot of the brewing maths I think it’s a good idea to know whats going on before you blindly plug figures into a computer. Doing calculations by hand first of all just gives you that little extra understanding.

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Separating Wort From Grain

RecirculatingDuring the mash the enzymes have done the job and extracted the sugars and dextrins from the grain to create a wort, now we need to get the wort out and leave the grain behind. This procedure is called lautering.

Earlier we looked at different types of mash tun and talked about the false bottom or manifold that allows the wort out but the grain is too large to pass through and is stopped from reaching the outlet. This is only part of the process, the manifold or false bottom is just the to stop large particles from running out the mash tun, it’s the grain and particularly the husks that are important to achieving a good run off. As you open the tap to the mash tun the wort starts running through the bed of grain compacting it, the very first running will be full of particles and flour that are the result of the crushing of the malt. As the grain bed compacts down the particles get caught in the husks and the runoff becomes clearer and debris free, it’s the grain itself that becomes the filter and a large part of lautering is controlling this flow through the grain bed to keep as much of these particles out of the wort and left in the mash tun.



As the first runnings come out the wort will be full of grain particles and debris, the first few litres should be drawn out into a jug and poured back into the top of the mash tun, recirculating it. Ideally we want the wort being run off to be a clear of debris as possible, after a few minutes of recirculation the wort should run relatively clear and the wort can be collected in the boiler.


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Sparging is the term used to describe rinsing the grain bed to extract as much of the sugar left in the mash as possible, the consequence of this sparge also increases the amount of wort collected from the mash. The liquor used in the mash is usually in ratio to the amount of grain used in the recipe, somewhere along the lines of 2.5 – 3.5 litres of water per kilogram of grain, this amount of liquor is then run off whilst the sparge is performed to reach the level of wort for the brew length.


Sparge liquor is heated to around 75 – 80°C this increases the solubility of the sugars in the wort and makes the whole mash less viscous which aids the run off. If the wort is run off too quickly the grain bed will compact to much and the sparge liquor won’t run through the grain bed resulting in a “stuck mash”. Running off and sparging slowly will keep everything flowing smoothly.

There are two main methods of sparging available to the homebrewer, one is fly or continuous sparging and the other is batch sparging both have their own advantages and disadvantages.

Fly Sparging

spargingContinuous sparging, also known as fly sparging is the most efficient method of sparging in the sense that it will extract the most amount of sugars from the mash. This method of sparging involves running of the wort as normal, starting slowly and recirculating to avoid compacting the grain too much. Then as the level of wort is just above the grain bed, slowly adding the sparge liquor at the same rate as the wort running out of the mash tun. The sparge liquor is sprinkled onto the grain bed to avoid disturbing the structure of it through a sparge arm or a similar sprinkling device. A sparge arm in most cases will look like a large T-shaped pipe with holes drilled all the way along it, the arm is suspended above the grain bed and the sparge liquor pumped through it. As the water is pushed through the sparge arm the whole thing rotates due to the way the holes are drilled, this evenly distribute the sparge liquor across the grain bed.

As mentioned before the extract of sugars from the mash is most often highest with fly sparging, this is why almost all commercial breweries use this method. The home brewer though may not or need not be as concerned with the extraction efficiency and more with time and the amount and cost of equipment as this method of sparging takes more of both. A method of sparging available to the homebrewer who doesn’t have the same concerns as their commercial counterparts is batch sparging.

Bach Sparging

Batch sparging is simpler and requires less equipment than the continuous version. The process involves running off the mash and recirculating as before to attain a clear run off, then collecting these first runnings until the mash tun is completely emptied of wort. The outlet is then closed and the mash tun recharged with sparge liquor to attain the required amount of wort for the brew length. The whole mash and sparge liquor are vigorously stirred to aid the extraction and rinsing of sugars and left to settle for around 15 minutes. The runoff process is then restarted with recirculation as before to collect the second runnings, the mash tun is emptied again and both runnings combined. The speed of the batch sparge is a definite advantage and the only real downside is a small loss in extraction, this might sound bad but on a home brew scale it relates to a relatively small amount of grain being added to the recipe.

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Performing A Mash Out?

What Is A Mash Out?

A mash out, put simply is a method of raising the temperature of the mash just before the sparge is started. Usually, the temperature of the mash is raised to around 75-77°C (167-170°F) or thereabouts which does a few things.

First off, all the activity of the enzymes working at converting starches to sugars is halted as the temperature deactivates them. The higher temperature also has the effect of making the mash less viscous and flow more freely.

Mash Out

So Why Perform A Mash Out

To be honest the only reason I would consider a mash out is if I thought there would be problems with the sparge getting stuck or not flowing freely. Using a mash out to fix the ferementable profile and stop any further conversion is in my opinion of minimal effect.

If you sparge continuously then you are going to be raising the temperature of the mash anyway as part of the process. This is what happens in commercial breweries that perform single infusion mashes. They have no way to raise the temperature of the mash except when running the sparge which will be with significantly hotter liquor at around 77°C (170°F)

So how do you know if you’re going to have issues sparging freely. It’s quite simple and something you should be able to tell before you even begin brewing. If there is a large quantity, say more than 20-30% wheat or oats for example the sparge will be more liable to getting stuck in part because they have no husks to act as a filter. Raising the temperature with a mash out increases the viscosity of the mash and frees everything up.

Another reason to use a mash out would be if you have a particularly thick mash i.e. the grain to water ratio is close. A thicker mash increases the concentration of sugars and consequently increases the viscosity making the sparge difficult. Similarly if for some reason over the course of the mash you lose a lot of temperature it has the same effect.

A good analogy of this would be to compare the thickness of the mash to oil in an engine. When the engine is running and heating up the viscosity of the oil changes making the oil flow more freely.

Performing A Mash Out

If you can apply direct heat to the mash tun then it’s simply a case of doing so and stirring the mash to avoid creating hotspots until you reach the desired mash out temperature around 75-77°C (167-170°F).

If you cannot apply direct heat to the mash tun then an addition of hot water is the simplest way of achieving mash out temperature. Take a look at the strike water temperature article and calculate the addition of water needed to raise the temperature as desired. A more complex version of this would be to do a decoction but frankly unless doing a decoction mash is more effect than it’s worth.

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