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Old 06-12-2012, 12:16 AM   #1
mashiox
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Jun 2012
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My friends and I are going to be doing a smaller batch of beer using an existing recipe we've made and done before. However it's written as a 6.5 gallon recipe and we plan on making a 3 gallon recipe.

Normally, when I scale something down I use a conversion factor I use the chemist's equation.

(Given unit x) * (Target Unit y)/(Target unit x) = (Given unit y).

Since the 6.5 gallon recipe isn't double what the 3 gallon would be, I'm not comfortable simply halfing it.

So one of the grains we put into the 6.5 gallon recipe is 3lbs British Pale Malt.
This is out of 8lbs of grain total.

Would the scale be best by calculating it as:

3gal * 3lbs/6.5gal

or something else?

 
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Old 06-12-2012, 12:29 AM   #2
ktblunden
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Grains should scale linearly, so yes that will work just fine. Be aware that hop utilization does not scale linearly, so you might need to use an online calculator to keep the same IBU level.

 
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Old 06-12-2012, 01:27 AM   #3
biochemedic
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Further to online resources, I know some brewing software allows you to directly scale down an entire recipe as an automated function...I use a stand alone program (ProMash) so I'm not sure if any of the online calculators do this...might be worth checking into.
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Old 06-12-2012, 03:10 AM   #4
ktblunden
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Beersmith also has easy scaling tools, but I assumed he wasn't using software since he didn't ask about it. Though you can always download Beersmith and use it free for 30 days.

 
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Old 06-12-2012, 03:11 AM   #5
mashiox
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Jun 2012
Chula Vista, CA
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Thanks for the help!

I was able to snag a trial of BeerSmith and let it scale down the hops for me.
I did manage to punch in the grain conversions and the qt/lbs ratio is really close.

The lack of information on the web about hop scales is disappointing. I will try to reverse engineer the function from BeerSmith, but that doesn't seem very likely without understanding Alpha Acids and IBUs.

I did some further research and found there are regrettably two IBU functions. Also I bought Ray Daniels' book "Designing Great Beers." Hopefully that will shed some light onto my problem.

If it isn't thread necroing, I'll post my found formula.

 
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Old 06-12-2012, 03:19 AM   #6
BigEd
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Nov 2004
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Quote:
Originally Posted by mashiox View Post
My friends and I are going to be doing a smaller batch of beer using an existing recipe we've made and done before. However it's written as a 6.5 gallon recipe and we plan on making a 3 gallon recipe.

Normally, when I scale something down I use a conversion factor I use the chemist's equation.

(Given unit x) * (Target Unit y)/(Target unit x) = (Given unit y).

Since the 6.5 gallon recipe isn't double what the 3 gallon would be, I'm not comfortable simply halfing it.

So one of the grains we put into the 6.5 gallon recipe is 3lbs British Pale Malt.
This is out of 8lbs of grain total.

Would the scale be best by calculating it as:

3gal * 3lbs/6.5gal

or something else?
The difference in size here is not significant as both 6.5 and 3 gallon batches can be considered small. Just use your 3/6.5 ratio (~46%) and I think you will be fine.

 
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Old 06-12-2012, 03:45 AM   #7
mashiox
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Jun 2012
Chula Vista, CA
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Thanks for the help!

I did manage to scale down my grain recipe nicely, and the qt/lbs ratio stayed very close. Also, I scaled down the mash pH recipe using the same conversion factors and it's dead-on to the original 6.5 recipe.

The hop scale is what is currently stumping me. I did read through my own research that I can scale it down approximately the same way as I did the grains, however, I'll be continuing to look for the exactly formula.

I did snag a trial of BeerSmith to get the quick scale for tomorrow however.

 
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Old 06-12-2012, 05:23 PM   #8
dcp27
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Quote:
Originally Posted by ktblunden View Post
Be aware that hop utilization does not scale linearly, so you might need to use an online calculator to keep the same IBU level.
as long as you also scale the boil size proportionally, hop utilization does scale linearly

 
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Old 06-13-2012, 06:55 PM   #9
mashiox
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Jun 2012
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Quote:
Originally Posted by dcp27 View Post
as long as you also scale the boil size proportionally, hop utilization does scale linearly
Please explain. What are we considering boil size? Mash+Sparge? Just mash?

 
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Old 06-13-2012, 07:39 PM   #10
dcp27
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Quote:
Originally Posted by mashiox View Post
Please explain. What are we considering boil size? Mash+Sparge? Just mash?
neither. boil volume is whatever makes it into the kettle for the boil. hop utilization is proportional to your boil gravity (sorta, its technically break material, etc), so as long as its the same with both batches then it scales linearly

 
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