Converting from 7 gallon boil to 3 gallon partial boil - Home Brew Forums

 Home Brew Forums > Converting from 7 gallon boil to 3 gallon partial boil

06-23-2010, 06:18 PM   #1
BogusOwnz
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Mar 2010
Lake Forest, IL
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I purchased "Brewing Classic styles" and it lists all recipes with a 7 gallon boil. It has the equation to convert the extract but after an hour of tinkering I just can't figure it out.

06-23-2010, 06:28 PM   #2
Nanobru
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Huntington Beach, California
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5/7= .71.4. So you would use 71.4% of the malt bill. Hops get tricky though, you could use the %, but it depends on what your AA% are. If you have a program like beer smith or promash its prettty quick work. On promash you would lock ingredients to batch size, and ensure your hop additions are correct.

06-23-2010, 08:03 PM   #3
rayg
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Quote:
 Originally Posted by BogusOwnz I purchased "Brewing Classic styles" and it lists all recipes with a 7 gallon boil. It has the equation to convert the extract but after an hour of tinkering I just can't figure it out.
What is it exactly you can't figure out?

Many formulas for converting all grain to extract recipe, for example:
http://www.brew-dudes.com/all-grain-...-conversion/78

Once you convert to extract, then multiply by 5/7 to correct for
the scale-down.

Ray
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06-23-2010, 09:07 PM   #4
BogusOwnz
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All recipes are based on a 7 gallon boil with 6 left at the end of the boil 5.5 going into the fermenter and 5 going into the keg or bottles. I don't have a turkey frier or big pot. It says you can do a partial boil with 3 gallons and then just topping it off at the end except the amount of extract you use has to be modified. For example It shows an IPA that calls for 9.75 pounds of LME but after this crazy equation it used for an example it comes out to 3.75 pounds of LME. So this is all based on pre boil volume.

06-23-2010, 09:42 PM   #5
mdwmonster
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Jan 2009
Kirkwood, MO
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Quote:
 Originally Posted by BogusOwnz So this is all based on pre boil volume.
Right, Jamil's book is written for full (7 gallon) boils with 5.5 gallons in the fermenter. Use the formulas in the front that he shows to scale down to a partial, and then top off to get to 5.5 gallons.

As he discussed in the front of the book, the only reason to do this is to get about the same wort SG as the recipe. Hop utilization is tied to wort SG. You COULD add all of the malt, but it will lower the IBUs from what is shown in the recipe. You COULD just boil all of the malt, then add more hops to get back to his IBUs - but doing the conversion is simpler (and cheaper).

06-23-2010, 10:16 PM   #6
BogusOwnz
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Mar 2010
Lake Forest, IL
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the problem i have is the conversion he talks about on pages 34-37 I just can't figure out.

06-23-2010, 10:23 PM   #7
midfielder5

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Jan 2009
San Francisco, CA
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i don't have the book or your problem, but I have seen this discussion (if it helps, which it might just confuse things!)
http://www.homebrewtalk.com/f39/part...gravity-95806/

06-24-2010, 02:31 AM   #8
BogusOwnz
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Mar 2010
Lake Forest, IL
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Wow after reading that thread maybe I need to just do 7 gallon boils. Although when I'm doing other extract brews after the steeping the directions usually have me add all the extract at once and it's usually to around 2 gallons of water. Why is this different? If I dilute it all at the end any way why woes it matter? Won't I get the same sg? The example recipe the book uses originally calls for 9.75lbs of lme for a full 7 gallon boil but after the equation and conversion to a partial 3 gallon boil it calls for 3.75lbs of lme. Ok I'm not master brewer but being able to produce identical end result 5 gallon batches using completely different amounts of lme does not seem possible.

06-24-2010, 12:53 PM   #9
david_42

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Do not change the amount of LME. Partial boils can change the IBUs, but sugar is sugar and you have to use the same amount to hit the SG. If you are really OCD, you can adjust the LME for a 5.5 gallon final volume vs a 6 gallon final volume.

I would not bother.
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06-24-2010, 01:34 PM   #10
mdwmonster
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If you’d rather not mess with the math, just add 1/2 of the extract when you start the boil, then and 1/2 at the end. There are a lot of posts on here about late extract additions - it has improved the quality of my brews.

What he is doing is accounting for the potential sugars in both the specialty grains and the extract. He calculates the contribution of the grains to the boil SG, and then subtracts that out of the boil SG. Then divides out to see how much extract is needed to make up the difference. Then ratios that out to a 3 gallon size. I don't have my book here at work, so I can't offer a better explanation, but that is what he is doing.

EDIT: Ok, looking at the book over lunch and I'll see if I can clarify. The steeping grains are contributing 24 degrees of gravity per pound, so you multiply the weight you have (1.25 lb in his example) by 24, then divide by the volume of your boil (3 gallons in his example). You subtract that amount (10 in his example) from what the recipe says the Boil SG is (55 in his example, using only the numbers after the decimal point), which leaves you with the degree of gravity that needs to come from extract (45 in his example). LME contributes 36 degrees of gravity per pound, so you divide that by your boil volume (3 gallons in his example) and then divide the needed SG by that number (45/12 in his example = 3.75 pounds of LME).

If you are sticking with 3 gallon boils, all of this works out to: Weight of LME = (Boil SG - 8xWeight of Grains)/12 (using the numbers in his example: 3.75 = (55-8x1.25)/12). You then add the remaining LME at the end of the boil.

Quote:
 Originally Posted by BogusOwnz being able to produce identical end result 5 gallon batches using completely different amounts of lme does not seem possible.
you are using the same amount of LME, just adding it at different times. He added 3.75lb of LME at the start of his boil, then added the remaining 6.5lb of LME at the end of the boil (Step 6 on page 38)

Not sure if I helped or muddied the water.....