High Gravity Biab In A Big Pot

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herbo

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Hi all,

I have read plenty about handling high gravity BIAB's in pots that are smallish (eg. 40lt urn) but haven't found much about brewing high gravity if the pot is not the limitation. I have a 100 litre pot and am looking to brew something like the Belgian Dark Strong Ale from Brewing Classic Styles. Aiming for an OG of 1.09 to 1.1.

Now normally I go for 25 litre batches in the 100 litre pot so it's not really that full when I do normal brews (i.e. OG 1.050). If I was to do a brew like the Belgian should I just go with the normal BIAB method? Remembering that the size of the pot is no limitation. I have read that some do like a double BIAB, as in split the grain bill into 2. Others would do some type of sparge to get more of the goodies from the grain bill. I have designed my recipe as normal with 72% efficiency in Beersmith, but now thinking I should adjust that efficiency down, or I suppose maybe I leave the efficiency as is but just expect a lesser volume (due to the larger grain bill absorbing more water).

Anyone that has done a high gravity like this care to comment on their experience?

Thanks,
Herbo
 
After all my reading the only thing I gathered was that the efficiency drops down quite a bit (like from 75% to 60%) so you may just need to increase your grain bill. I assume this is due to the lower kg/lt ratio.

Be interested in reading others replies.


Fi
 
If the size of the pot is of no limitation, then you don't have a problem at all.

It then comes down to using certain amounts of water in the beginning, and a pre-boil volume, to calculate how much wort you will have at the end (for fermenting).

You need to take into account water absorbtion via the grain, aswell as evarporation rate during the boil.

As a simple guide, you multiply your desired ferment volume by the predicted evaporation (generally from 5 to 15 percent). So ferment volume is 25, multiply that by 1.15 (evaporation amount of 15% for 60 min boil) gives you 28.75 L. That's the maximum amount of water you can have pre-boil. Now we can assume that each kilogram of grain absorbs 0.6L of water, so you should be using roughly 10kg of grain, therefore you will lose about 6L to the grain alone. Add that to our 28.75 to give us 34.75L.

Therefore the maximum amount of water you can use in the recipe is 34.75L (round up to 35L). Now if you like you can divide the amount of water into mash water and sparge water, say 25L for the mash, and 10L for sparging.

So to summarise, for a belgian strong ale (OG of 1.100) you will require about 10kg of grain for a 25L batch based on 72% efficiency.

You can use a total of 35 litres of water, aiming for a pre-boil volume of 28.75L, and a fermentation volume of 25L.

Hope that helps.
 
I've been trying to wrap my head around this as well, as I plan on building a BIAB system - essentially a DIY Braumeister. I think the gravity limits on that system are kettle size, and the malt tube configuration, which seems to need a certain volume to work properly. Please correct me if I am wrong here.

From what I can gather, the gravity limit of any BIAB is limited by:

Kettle size - if it doesn't fit...

Preboil volume - if you need to end up with 5.5 gallons (yes, I am from the states, but their forums mostly suck), you're limited by the amount of water you can add. I think this is demonstrated by Little Pony's math.

The finite gravity limit of first runnings? - From my experience, I have never been able to get above 1.082 or so without sparging. I've read similar accounts.

Comments appreciated!

Michael
 
So to summarise, for a belgian strong ale (OG of 1.100) you will require about 10kg of grain for a 25L batch based on 72% efficiency.

You can use a total of 35 litres of water, aiming for a pre-boil volume of 28.75L, and a fermentation volume of 25L.

Hope that helps.

Definitely helps and I think I understand most of what you've calculated out. I guess my most important question is should I be expecting to get anywhere near 72% efficiency with a 10kg grain bill aiming for OG of 1.1? Or will I as Mike mentioned only make it to 1.082 or thereabouts?
 
Definitely helps and I think I understand most of what you've calculated out. I guess my most important question is should I be expecting to get anywhere near 72% efficiency with a 10kg grain bill aiming for OG of 1.1? Or will I as Mike mentioned only make it to 1.082 or thereabouts?

Just to be clear, I am talking about 1.082 (or thereabouts) into the kettle. The "rest" of the gravity would come from boil reduction.

Michael
 
To be safe you could always just scale efficiency down to %60, it will only cost an extra few $$. If you hit 60% efficiency then let it be, if you get higher efficiency, you can always water down later and you will end up with more beer! It's win-win.
 
I'd recommend not bothering about being "purist" about your BIAB process, and doing a dunk-sparge. For a recent 1.080 baltic porter, I withheld 6L of my pre-boil volume and did two 3L dunk-sparges with tap water. My mash efficiency came out at 80%, which is pretty good, I reckon, for a wort of that gravity.

cheers,
T.
 
A purist BIABer is like a clothed nudist. :unsure:
 
Quite. But often enough as soon as someone says "sparge" people complain that it's not "true" BIAB anymore. Pedants! ;-)

Off to aerate and pitch my schwarzbier,
T.
 
I would suggest possibly doing an extended boil, this will allow you to have more starting water, which will increase your efficiency. Perhaps aim for 70%

I regularly do 10KG double batch biabs, but generally I'm aiming for circa 1.052

With single batch full volume biabs I get about 93-97% efficiency
With the double batches the gravity is higher and mt efficiency drops to 81-85%

I once tried a 12.5KG bill, which meant even higher concentration. Result was 60% efficiency. Maybe I didn't agitate enough


So, my advice would be to perhaps double your boil so you can double your evaporation. This will allow you to have more water in your mash. And then do a dunk sparge with some extra reserved water. And plan on a lower efficiency, at least 70%

Agitate the mash/check temp every 15 mins. I have found this greatly improves efficiency. I also do a 90 min mash + mashout
 
I am unsure if it has been mentioned, but it is a good idea to ensure you both stir well and give a good mash out step, potentially at the high end to assist yield.
 
Quite. But often enough as soon as someone says "sparge" people complain that it's not "true" BIAB anymore. Pedants! ;-)

Off to aerate and pitch my schwarzbier,
T.

80% of any population look for the rules to follow.
15% adapt.
5% innovate.

And 43.4% of statistics are made up on the spot.
 
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