Author Topic: How large an effect can increased volume have on lower OG?  (Read 989 times)

Offline Beer Monger

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Someone help me with the math here.

If I'm brewing a 5 gallon batch and want an OG of, for example. 1.060, how much should I expect my OG to drop if I wind up with six gallons of wort isntead of 5? 

I guess the basic question here is, if you have wort that's 1.060, what would the reading drop to if you added a gallon of water? 
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Offline denny

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Re: How large an effect can increased volume have on lower OG?
« Reply #1 on: May 02, 2011, 09:04:42 AM »
Easy....5 gal. at 60 gravity gives you 300 gravity units (5*60+300).  If you have 6 gal., it becomes 300/6=50.  So the gravity would be 1.050.
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Offline Beer Monger

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Re: How large an effect can increased volume have on lower OG?
« Reply #2 on: May 02, 2011, 09:06:23 AM »
Easy....5 gal. at 60 gravity gives you 300 gravity units (5*60+300).  If you have 6 gal., it becomes 300/6=50.  So the gravity would be 1.050.
OK.  Thanks, Denny.  That would partly explain the lower OG on my batch this weekend.  I think I wond up with 6 gallons instead of 5.  I must have over-compensated for the losses I was experiencing when doing 10 gallon batches (the batch this weekend was 5). 
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Offline narvin

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Re: How large an effect can increased volume have on lower OG?
« Reply #3 on: May 02, 2011, 09:31:35 AM »
To make it even more simple: gravity is points/gallon, so if your volume increases by the ratio 6/5, your gravity lowers to 5/6.

Now, you might get a little bit higher efficiency from the longer sparge, but that will be small compared to the loss of 16.66667% due to dilution.
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Offline narvin

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Re: How large an effect can increased volume have on lower OG?
« Reply #4 on: May 02, 2011, 09:35:29 AM »
Easy....5 gal. at 60 gravity gives you 300 gravity units (5*60+300).  If you have 6 gal., it becomes 300/6=50.  So the gravity would be 1.050.
OK.  Thanks, Denny.  That would partly explain the lower OG on my batch this weekend.  I think I wond up with 6 gallons instead of 5.  I must have over-compensated for the losses I was experiencing when doing 10 gallon batches (the batch this weekend was 5).  

Just curious... why do you think you'd get greater losses in a 10 gallon batch?  Things like mash tun and boil kettle dead space, as well as boil off, should be a fixed volume and not proportional to your batch size, so you'd have less loss in a 10 gallon batch as a percentage.  Unless you're using different equipment, that is.
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Offline richardt

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Re: How large an effect can increased volume have on lower OG?
« Reply #5 on: May 02, 2011, 09:45:17 AM »
I can think of one situation where the (lautering) efficiencies would be different between a 5 and 10 gallon batch, and a low-gravity versus a high-gravity batch, especially with a round 10-gallon Rubbermaid/Gott cooler due to grain bed compaction.  There is just too much height to the grain bed given its base.  You can still get the sparge done, but it takes a lot longer.  If you're regularly doing large batches and/or high gravity brews, go for the bigger and rectangular cooler in order to keep the grain bed height low relative to the base.

Offline Beer Monger

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Re: How large an effect can increased volume have on lower OG?
« Reply #6 on: May 02, 2011, 09:56:49 AM »
Easy....5 gal. at 60 gravity gives you 300 gravity units (5*60+300).  If you have 6 gal., it becomes 300/6=50.  So the gravity would be 1.050.
OK.  Thanks, Denny.  That would partly explain the lower OG on my batch this weekend.  I think I wond up with 6 gallons instead of 5.  I must have over-compensated for the losses I was experiencing when doing 10 gallon batches (the batch this weekend was 5).  

Just curious... why do you think you'd get greater losses in a 10 gallon batch?  Things like mash tun and boil kettle dead space, as well as boil off, should be a fixed volume and not proportional to your batch size, so you'd have less loss in a 10 gallon batch as a percentage.  Unless you're using different equipment, that is.

I don't think I'll get greater losses in a 10 gallon batch.  I don't believe I said that.    

The last few batches I made (which were 10 gallon batches), I was coming up a bit short.  What I was saying is that I must have over-compensated for equipment losses (by adding too much more water to the mash & sparge).  So even though this batch was only 5 gallons, my over-compenstation means I wound up with over 5 gallons.  

No big deal.  So I have more beer that's slighly less potent.  
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Offline morticaixavier

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Re: How large an effect can increased volume have on lower OG?
« Reply #7 on: May 02, 2011, 10:07:42 AM »
Beersmith has a dilution calculator that seems to work pretty well also. As Denny pointed out the math is pretty easy but if you have the soaftware it's there also.
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Offline Beer Monger

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Re: How large an effect can increased volume have on lower OG?
« Reply #8 on: May 02, 2011, 10:11:04 AM »
Beersmith has a dilution calculator that seems to work pretty well also. As Denny pointed out the math is pretty easy but if you have the soaftware it's there also.
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