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Batch Sparging a Large Grain Bill

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tbone

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For my first AG, I was able to split my sparge into two equal parts as suggested on this forum but with this large of a grain bill (17lbs)the two equal sparge volumes are to small. I am doing a 90 min boil and am using a pre-boil volume of 7 gallons. (Hopefully the 7 gal will get me 5 gallons)
Here is what I want to do.
Do a mash out with 2 gallons close to boiling.
Sparge with 1.85 gallons at 168.

This will give me just a bit over 7 gal figuring 1.25 qts per lb of grain with an absorption rate of .12gal/lb of grain.

Will this be an efficient way to sparge this large amount of grain or is there a better way?
Thanks
 
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tbone

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Does it matter how small your sparge volume is?
And does 7 gal pre boil for 90 minutes look good for a 5 gallon batch?
I am new to AG (2nd batch) and don't have my absorption and evaporation rates down yet.
 

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I'm finding that it takes time to figure out absorption and boil off rates. For reference, I'm doing a 5.5 batch today with 2.5oz hops and I'm starting with 7.5 gallons in the keggle...
 

Bobby_M

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If you want to maximize your efficiency, don't add the 2 gallon mashout water. If 2gallon mashout plus 1.85 sparge was going to hit your volume, I'd recommend taking a first running first, then sparge TWICE with 2 gallons each at 180F.

If you have an accurate way of measuring your runnings volume, just figure out how much you're missing when you take your first running. If you want 7gal preboil and your first running was 3 gallons, you're right on with two 2-gal sparges. If you only get 2.5g out of first running, then make the sparges 2.25 each. Pretty simple in practice.
 
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tbone

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I screwed up the first time and did not measure the wort collected to figure the absorption rate. I will this time. I boiled for 60 min for the first batch and used 6.5 gallons and ended up with around 5.25 gallons.
 
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tbone

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Bobby. So you are saying not to raise the first running temp to around 168, but instead - just collect the first running as is and then do two sparges of 2 gallons at 180? I am assuming that the two sparges at 180 will bring the grain bed temp up enough to maximize extraction.
 

Orfy

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You also need to know what the dead space is in your kettle.
If not you need to know how much you leave behind with the hops.

If you have no dead space/loss then yo have an evaporation rate of ~20% hour.

So you should loose 30% over 90 minutes
30% of 7g = 4.9g
 

Bobby_M

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tbone said:
Bobby. So you are saying not to raise the first running temp to around 168, but instead - just collect the first running as is and then do two sparges of 2 gallons at 180? I am assuming that the two sparges at 180 will bring the grain bed temp up enough to maximize extraction.
Exactly. The intended result of a mashout is kinda erased due to the fact that you're adding fresh water to an already massively sugar saturated mash. You increase your efficiency substantially by getting all that sugar out prior to the fresh water rinse. It's great to raise the mash temp of course, but that's why the addition of hotter sparge water works. I go with 180F on each sparge but you could eek out a few more points by making the first one 185 and the second one 175, but that's a pain.

My first sparge get me to about 162F and the second up to 169ish.
 
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tbone

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Thanks guys. I am planning on brewing tomorrow. I'll let you know how it turns out.
 

FlyGuy

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You have already touched on this when you questioned the use of a small sparge volume, but that big a grain bill is going to probably lower your efficiency by a significant amount. With large grain bills and a fixed volume of wort and fixed boil time (say 5 gallons after 90 mins), the proportion of strike water to sparge water changes. Or, in other words, the amount of sparge water relative to strike water decreases as the grain bill increases.

There are two common ways to deal with this:

Sparge more and collect a larger volume of runnings, necessitating a longer boil to get down to 5 gals (say 2.5 hours instead of 1.5). But this may generate problems with 'caramelization', which could be an issue for some styles.

Accept that you will lose efficiency, and increase your grain bill to compensate. Then you can keep your wort volume and boil time the same as smaller gravity batches. The difficulty here is knowing how much efficiency you will lose. On my system, the difference in efficiency between a 1.055 batch and a 1.090 batch is about 8 - 10%, but I am sure that varies widely among breweries.

Hope that brew goes well! (I just did a SMALL grain bill batch -- an English mild ale -- and I had some opposite problems and I am still kicking myself for how I handled it all! Live and learn!).

Cheers! :mug:
 
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tbone

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Flyguy I see what you are saying. I don't have any extra grain and thought about adjusting the hops to account for the lower expected gravity. However the recipe calls for continuous hopping - mixing all together and adding .2 oz every 5 minutes for the 90 min boil. Continuous hopping doesn't fit with Beersmith so I am left to guess. I think that I will go ahead and brew and see what happens. I love hops so if it is over-hopped I MAY enjoy it.
 

FlyGuy

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If that's the case, then I would just increase your pre-boil volume to accommodate a larger sparge volume, and then just boil down to your target volume. Just remember to time your hop additions correctly (i.e. countdown from the end of your boil -- hopefully you can predict how long it will take).

Best of luck! :mug:
 
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