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Old 12-01-2011, 02:47 AM   #1
zyx345
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Default Partial Mash and Off Starting Gravity Reading

I just did Austin Home Brew's Belgian White Partial Mash kit. Included:

-3# of grains
-4# of wheat DME

I used DeathBrewer's partial mash instructions from this thread: http://www.homebrewtalk.com/f39/easy...ng-pics-75231/ and I did a partial boil and added top off water at the end in the carboy.

I mashed at 155 for an hour in 2 gallons of water. I sparged at 170 for 10 minutes in approx. 1 gallon of water.

After adding my top off water, the carboy shows darker coloring on the bottom and slightly lighter in the middle to the top.

I took a gravity reading off the top of the carboy after adding my top off water using a turkey baster and it came in ridiculiously low, 1.031 and the sample looked much lighter in color than the entire carboy. The kit says you should be around 1.048.

Did a search and found this thread on a similar experience: http://www.homebrewtalk.com/f37/way-...reading-46868/

My question is, does the extract sink to the bottom then get mixed during fermentation? I am used to my old Coopers fermenter with a spigot at the bottom for taking OG readings.

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Old 12-01-2011, 03:26 AM   #2
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It's a really common problem in the extract, partial-boil, top-off scenario. I bet the question comes up on here on a weekly if not daily basis. When the yeast become active, there will be lots of movement of the wort/beer, so it will definitely not stay stratified.

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Old 12-01-2011, 03:39 AM   #3
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Would a post-aeration reading be more accurate?

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Old 12-01-2011, 12:58 PM   #4
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Quote:
Originally Posted by plumbob View Post
Would a post-aeration reading be more accurate?
Generally yes, but it might depend on how you aerate (air stone vs shaking or stirring). Often it takes a lot of stirring/churning to get the sample to be uniform.
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Old 03-06-2012, 02:30 PM   #5
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Did another PM brew with 6# of grain and 2.5# of DME (late addition @ 15 minutes left)and had the same problem with seperation. I shook the carboy with 5 gallons of wort in it and it still showed seperation.

Is there any way to get an accurate OG reading with extract brewing?

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Old 03-06-2012, 02:36 PM   #6
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In the extract brews I have done which weren't too many we got quite accurate OG readings by taking after aeration. We would usually aerate by pouring back and forth between 2 6.5 gallon sanitized buckets about 5-6 times. Since we were pitching dry yeast packs (mostly Us-05) in our DME and LME batches, the resulting foam at the top made a perfect bed for the pitch, and they usually were very active within 3 hours. Prior to pitching the consistency of the wort seemed to be quite good after that heavier aeration. These OG readings were consistent, as we took a few to be certain.

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Old 03-06-2012, 05:03 PM   #7
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Quote:
Originally Posted by zyx345 View Post
Is there any way to get an accurate OG reading with extract brewing?
yes, measure it before you top off then calculate to the batch volume

OG = post-boil OG * post-boil volume / full volume
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