This guide will show you step by step how to get started with all-grain/partial mash brewing to create a delicious oatmeal stout. We strongly advise that you view our page which runs through all the steps in detail before starting.
This process uses a three-vessel brewing system that has been traditionally been used in homebrewing. As discussed in the sidebar on page 83 there are other options such as the Brew in a Bag method, and hybrid approaches can be used. Traditionally, homebrewers have used a system consisting of a boiling vessel, a mash/lauter tun, and a hot liquor tank, the last of which is used to supply hot water to the mash and for sparging. These instructions also presume that you are batch sparging. While both batch sparging and fly sparging can give excellent results, batch sparging is presumed as it is a simpler method for the new all-grain brewer.
Here we’re going to brew a delicious, traditional oatmeal stout. We’re only going to use one hop and it’s for bittering, this is because the focal point will be the oats and the roasted barley. A clean yeast must be used.
Ingredients & Information
- 4.5 kg. Marris Otter
- 1 kg. Flaked Oats
- 700g. Roasted Barley
- 200g. Chocolate Malt
- 30g. Chinook Hops (added at the start of the boil)
- Wyeast 1056 American Ale yeast
- Original Gravity Estimate 1.064 (based on 70% efficiency)
- Final Gravity Estimate 1.015
- IBU 32
Step 1. Yeast
If you’re using liquid yeast and plan to use a starter, you will need to prepare the yeast a few days before brew day. You can use dry yeast without a starter, but for best results we advise you rehydrate the yeast in warm water before pitching it. Visit this page to learn how to make a starter.
If you’re following our recipe, you will need to make at least a 1-liter starter two days prior to brew day.
Step 2. Clean & Sanitize
Just like with extract brewing, cleanliness and sanitization are so important. Your equipment must remain clean at all times, anything which will come into contact with the wort after the boil must be sanitized.
Step 3. Dough-In
Actually combining the grain with the mash water is known as “doughing-in”. First, bring your mash water to your strike temperature. The strike temperature is the temperature of the water as it is combined with the grains. Adding the grains causes the temperature of the strike water to drop; generally, the water will drop by around 10 degrees Fahrenheit upon addition of the grains.
We recommend that you preheat your mash tun in order to prevent any further temperature loss. Some homebrewers like to bring the strike water to the appropriate temperature in the mash tun; if you’re going to do this then don’t preheat the mash tun itself. If you’re using a separate mash tun, you should preheat it by adding around half a gallon of boiling water to it for around 10-15 minutes (and then removing the water).
Regardless of if you add the grain to the water, or the water to the grain, it is vital that you thoroughly mix the grain; if you do not, dough balls will form. Grain at the centre of these balls will not correctly undergo the conversion process, resulting in lower extraction efficiency.
If you’re following the Oatmeal Stout recipe, bring around 4.5 gallons of water to 165 degrees Fahrenheit prior to mixing in your crushed grain. You’re aiming for a mash temperature of 154 degrees Fahrenheit. Make sure that you thoroughly mix your grains in to prevent the formation of dough balls. Add hot or cold water as required in order to achieve your target temperature.
Step 4. Mash
Once the target temperature has been reached, you will need to steep the grain at the mash temperature for around one hour; this ensures that the starches have been fully converted into sugars. If your mash tun is a converted picnic cooler, all you need to do is cover the mash and leave it. However, if your mash tun isn’t insulated, wrap it in a blanket or something similar to provide insulate it. It is acceptable for the temperature to drop slightly, but you want to keep it as close to the target temperature for as long as possible.
Step 5. Prepare the Sparge Water
As the end of the mash approaches, you will need to prepare your sparge water. The key to sparging is making sure that you use enough water to meet your target volume at the end of the boil. First, you need to determine how much water you require. There are two main factors in determining this, the amount of water which is absorbed by the grain throughout the mash and the amount of water which is evaporated and therefore lost, during the boil.
Throughout the mash, the grain will absorb around 0.1 gallons of water per 0.5kg of grain. Our oatmeal stout recipe uses 14 pounds of grain; therefore we can assume that 1.4 gallons of water will be absorbed. It is usually assumed that 1 gallon of wort will be lost during the boil, meaning you will lose around 2.4 gallons of water between the boil and the mash. Because you began with 4.5 gallons of water in dough-in, and the target volume is 5.5 gallons of water, you will need to introduce another gallon of water, in addition to replacing the 2.4 gallons you’re going to lose through absorption and evaporation. As such, you will want to sparge with 3.4 gallons of water, which we can round up to 3.5, just to make things easier.
Heat the sparge water to somewhere between 170 and 180 degrees Fahrenheit.
Step 6. Lauter and Sparge
If you will be performing batch sparging, completely drain all the wort in the mash tun into your boiling vessel. As discussed, begin by extracting one or two liters of wort and reintroducing it back into the mash tun; the vorlauf. Continue doing this until the wort which is drained has no grain particles in it. Once you have finished the vorlauf, drain the wort as quickly as you like, as channeling is not an issue. As soon as the mash tun has been totally drained, move the hot sparge water to the mash tun and stir the water to disrupt the grain bed. Leave it for 5–10 minutes to settle, afterwards repeat the vorlauf and then extract the sparge water into the boiling vessel.
If you will be performing a fly sparge, you must remove the wort gradually in order to prevent channeling. Conduct the vorlauf, and allow the wort to gently drain until the wort reaches a level just above the grain bed. Slowly introduce around an inch or so of sparge water on top of the grain bed. Some homebrewers prefer to add this water by ladle to avoid disturbing the grain. As the wort is slowly removed from the mash tun, replenish the sparge water, until you have no more sparge water left and have completely drained the mash tun. This process should take around 45 minutes.
Step 7. Boil
Once lautering and sparging has been completed, you should have around 6.5 gallons of wort in your boil vessel. Start the boil, but be wary of boilovers. As the hot break on the surface begins to form, you can continuously stir the wort, reduce the heat, or temporarily remove the pot from heat to prevent a boilover.
Once you have brought the wort to a boil and progressed past the hot break, you should add your bittering hops. In our recipe, we’re only using one type of hop – bittering – add it now. If the recipe you are following utilises flavour or aroma hops, add these within the last 15 minutes of the boil.
Step 8. Chill
Once the boil has been completed, the wort needs to be chilled as fast as possible so that a cold break forms. Wort chillers or ice baths can be used to achieve this, with wort chillers doing the job quicker.
Step 9. Whirlpool
Once the wort has been chilled, we need to move it to the fermentation vessel in order to pitch the yeast. Hops, excess grain and material which was formed during the boil all needs to be removed. Whirlpooling is an easy way to do so.
Fundamentally, it involves stirring the wort in a circular fashion. As the wort moves around the boiling vessel, any particles will gradually shift into the centre. Once the wort has stopped moving, it can be drained or siphoned from the sides, therefore leaving the unwanted materials in the middle. While you want to remove as much of this unwanted material as possible, you do not need to go over the top, as it is unlikely that it will have a significant on the final beer.
Step 10. Ferment
Once the beer is in the fermentation vessel, it needs to be vigorously aerated in order to give the yeast the oxygen that it requires.If your fermentation vessel is a bucket, pass the beer back and forth between the boiling vessel to splash it around. If your fermentation vessel is a carboy, balance it on one edge and rotate back and forth to shake up the beer, do this for around 5 minutes.
Now the beer needs to be left to ferment for at least two weeks, if not longer. The only way to know for sure that fermentation has finished is by using a hyrometer, when the hydrometer reading has remained the same for three days in a row, you can be pretty certain that fermentation has finished. You’re now ready to bottle/keg the beer!