When I started the hobby and made some research about recipes, equipment and raw materials, I found that almost everything was in some kind of codified volume : 5 gallons. The recipes I found were for 5 gallons of beer with their respective amount of grains, hop additions and yeast. The equipment was mysteriously listed for 5 gallons, like the carboys, the coolers for the mashing and the fermenters. I thought it was a holy number and always followed the instructions: everything for 5 gallons.
Then the time came where I could start buying new equipment and found a boil kettle that was 9 gallons. I thought it was weird, because everything I had was 5 gallons and those 4 extra gals were for more free space and to avoid boil overs (the addition of hops when the wort is boiling and you don’t have some space in the kettle is a headache). After that, I started tweaking around the recipe, the efficiency of the system and realized that I could tweak another variable: the final volume. I worked the recipe as a mathematical equation: if you have X of 2 row malt, then 1.84x (scaling from 5 to 9 gallons for 8 gals of beer) must do the trick. I made the same with the water, hops and yeast. Hell, I was wrong…
On brew day, everything went wrong: the tun was so full of water and grains that I had to drain some water liquid, there was a stuck mash, and the Original Gravity (OG) of the wort was too low, and the bitterness higher than expected. That was the time I realized that brewing larger batches wasn’t just as straightforward as I thought. When brewing more than 5 gallons, there are some variables, which are correlated, that must be taken in account:
1. Capacity of the equipment (Mash Tun, Boiling Kettle and fermenter).
2. Efficiency that can be achieved with the system.
3. Expected OG.
Understanding these variables will guide the brewer to know how many malt and hops must use be used to achieve X Original Gravity with a Y efficiency. Let’s go deeper into each one of the points:
Capacity of the Equipment for Big Batches
It’s important to know how much volume the tuns can hold. It’s easy to lose track of the fact that water and grains can impact the total volume of the mashing. If the mash tun capacity is of 7 gals, the brewer can’t expect to be capable of mash 7 gals of water mixed with grains. The grains will occupy space and, if not taken in account, there will be a flood at the moment of the dough in. There are mathematics ways to calculate these volume of water + grains, but, thanks to the technology, we have brewing software , which can help you the brewer out to know how much capacity the brewer tuns must have in order to brew X volume of beer.
The Boiling Kettle capacity is important too. If it fits the exact volume of wort, there will be some spilled liquid by the vigorous boil and a 100% guarantee that there will be a boil over when adding the hops or boiling off the hot break (there is a reaction when adding hop pellets that a lot of foam is created and everything starts to flood. This can be countered by a water sprayer to “destroy” the foam, but it is a headache the that most brewers want to avoid.)
Finally, the fermenter. If the fermenter is the exact volume of the wort coming in, there will be a 100% assurance that there will be a mess when the fermentation starts. Yeast will start to devour the sugar and a Krausen will form (a foam of proteins, hops and yeast). If the brewer is not armed with a blow off tube, the airlock can be clogged by the Krausen resulting in pressure building up. If it’s not handled, the fermenter can just launch the airlock out. Beer and yeast will be in all over the place. Changing the airlock is a headache because it has to be done several times until fermentation is less vigorous and the contamination hazard is very high when doing this. The correct way to counter attack this is to build a blow off tube that let the Krausen flow from the fermenter to a bucket/bottle with some sanitizing solution; or have a fermenter with more capacity (20% is recommended).
Big Batches & Efficiency
When brewing a high volume of beer, the brewer must take in account that the efficiency that he/she is used to while brewing 5 gals of beer is going to change. This is often related to a more compact mash (less water to grain ratio) that gives less space for the malts to interact with the water and covert the whole starch (enzymatic activity), or even related to the difficulties to mix the mash with all the extra grains (easier to mix 10 pounds of grain than 30 pounds). This variable is not as easy to predict as the other ones, like having some extra space in the mash tun or boiling kettle just in case. The only way to discover the new efficiency is by brewing. This uncertainty is awful at the beginning, but it’s the only way to understand it. Here’s an example:
The brewer is used to have a 70% efficiency when brewing 5 gals, and expect a wort of 1.05 points of gravity. The brewer uses the same malts and just scales the recipe x3 (moving from 5 gals to 15 gals). At the end of the brew of 15 gals, the brewer achieves a wort of 1.045. This means that there is a drop of 7% in efficiency. An adjustment must be done in order to counter this by:
1.- Adding more malt or extract (Dried/Liquid Malt Extract).
2.- Incorporating extra steps in the brew, like a fly sparge or mixing the mash more often. Or…
3.- Choosing a different method of mashing, like changing from BIAB (brewing in a bag) to a false bottom mash tun to be able to do a sparging/lautering.
There’s another option but it is not recommended. This is milling the grains with less space between the rollers, giving a finer grist. This actually elevates the efficiency, but at the cost of a latent danger of a stuck mash because of all the flour created. This can be avoided if you’re using the brew in a bag method.
Another thing to consider is the heat retention of your mash and strike water. The larger the volume of your mash, the slower it will lose temperature. This also means that 170F strike water in a 5 gallon mash may be too hot for a 10 gallon mash, resulting in a correction being needed or a high mash temperature.
With Big Batches, and Standard Size Batches, Everything is Connected
In brewing everything is connected and we can have a “butterfly effect”. A lower gravity from the lower efficiency in the mash, can cause the wort after the boiling to be more bitter (utilization of hops is higher with less sugars dissolved), ending in the worst case in a beer quite different than expected. Even stuff like the gas/electricity that is going to be used to bring the wort to boil and the time extension to chill it has an impact that is important to take in account while scaling.
Knowing the efficiency and implications of the new system can be challenging and time consuming but it will give the brewer the freedom to brew larger batches of beer with certainty in the numbers, which can be translated into certainty of the resulting beer.
A brew size of around 200 liters therefore seemed about right to start with and could be fitted into a small-purpose built (3.5m x 4.0m) brewhouse in my garden. Getting the structure built was relatively easy using our regular Portuguese builder who is talented at making new features, additions, and extensions in a way that captures our traditional property architecture. For the kit, I wanted to replicate large-scale breweries as much as possible, rather than settle on home brew adapted buckets and pots. This meant going for purpose-built, stainless-steel vessels throughout. BrewBuilder in the UK supplied me with a 200-litre hot liquor tank (HLT), mash tun, and boiler, together with two 100-litre …
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