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Old 03-10-2011, 06:49 PM   #1
william_shakes_beer
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Brewed my first batch 3 weeks ago, setting up to bottle next weekend.

It was a Brewers Best imperial nut brown ale ingredients kit. Followed all the directions, except instead of 2.5 gallons I boiled 3 gallons to account for boil off. The instructions predicted an OG of 1.071-1.075, I ended up after topoff with 1.06. What factors could account for the lower OG? I topped off to 5 gallons before taking the reading. Should I adjust topoff volume to get the target OG or am I within the expected tolerance? Boil was on an electric stovetop, a gentle rolling boil after steeping grains were removed, never saw a "foaming" stage to speak of.

Ingredients follow

4 OZ black patent
4 OZ chocolate
8 OZ victory
6.6 LB amber LME
2 LB amber DME
8 OZ maltodextrine

1 OZ columbus hops bittering (60 min)
1 OZ williamette flavor 15 min
1 OZ williamette aroma 5 min



 
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Old 03-10-2011, 06:54 PM   #2
stratslinger
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Most often this is just a case of not having mixed the top-off water sufficiently with the wort in the fermenter. When brewing from extract kits, it's very hard to actually miss the OG. It's also quite difficult (certainly not impossible!) to get the top off water mixed in well enough to get an accurate OG reading.

That said, once the Yeasties get to work, they'll certainly mix things up sufficiently, so it's not like there's any real trouble beyond flukey OG measurements.

I wouldn't worry about making any adjustments.



 
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Old 03-10-2011, 06:58 PM   #3
dancness
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Well it's possible that you didn't get the maximum amount of sugars from the specialty grains.

I know I was guilty of this my first time around, I tied my grains too tightly in the muslin bag, which trapped some of the sugars in. Also, I've been watching brewingtv.com and what they do is they steep the grains in a very loosely tied muslin bag in about 2 gallons of water. Then at the end of the steeping time, they put the muslin bag w/ the grains in a strainer over the boil pot and pour about 1/2 gallon more steaming hot water over them, which helps to extract a lot of the remaining sugars from all the space between the grain.

The other possiblity is your wort was not fully mixed with your top off water before you took a reading.

Those are the only things I could think of.

 
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Old 03-10-2011, 07:18 PM   #4
supermoth
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What temperature was your wort when you took the gravity reading? Hot wort will have a much lower gravity.

 
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Old 03-10-2011, 07:26 PM   #5
Revvy
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It's a pretty common issue for ANYONE topping off with water in the fermenter (and that includes partial mashes, extract or all grain revcipes) to have an error in reading the OG...In fact, it is actually nearly impossible to mix the wort and the top off water in a way to get an accurate OG reading...

Brewers get a low reading if they get more of the top off water than the wort, conversely they get a higher number if they grabbed more of the extract than the top off water in their sample.

When I am doing an extract with grain recipe I make sure to stir for a minimum of 5 minutes (whipping up a froth to aerate as well) before I draw a grav sample and pitch my yeast....It really is an effort to integrate the wort with the top off water...This is a fairly common new brewer issue we get on here...unless you under or over topped off or the final volume for the kit was 5 gallons and you topped off to 5.5, then the issue, sorry to say, is "operator error"

If your target volume was correct, then it will be fine.

More than likely your true OG is really what it's supposed to be. And it will mix itself fine during fermentation.
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Old 03-10-2011, 07:53 PM   #6
surferdrew
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Quote:
Originally Posted by supermoth View Post
What temperature was your wort when you took the gravity reading? Hot wort will have a much lower gravity.
if you don't use brewing software that can calculate this for you, here is a great table for future reference if you take a gravity reading at a specific temperature:

Hydrometer Temperature Correction Chart

As important, however, is at what points to measure your gravity.

Since you are doing a partial-boil, whether you do all-grain or extract, it is essential to measure your gravity after the boil.

If its too low....keep boiling or add more extract.

If its too high...add top-off water to bring it to the desired gravity.


As an all-grain brewer, I measure gravity at many points throughout the process. I measure my first mash runnings, halfway through the sparge runnings, and then towards the end of the sparging process. I measure my pre-boil gravity to measure my mashing efficiency and to calculate if I need to adjust anything to my boil or to add or reduce adjuncts such as sugar.

However, with extract brewing, you don't have to worry about any of that. Just have to know your post-boil gravity (remember to adjust based on temperature) and then adjust accordingly.

 
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Old 03-10-2011, 08:01 PM   #7
MaltMonster
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Quote:
Originally Posted by dancness View Post
Well it's possible that you didn't get the maximum amount of sugars from the specialty grains.
Correct me if I'm wrong, but my understanding is that specialty grains with extract kits don't provide any fermentable sugars. They only contribute flavor and color.
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Old 03-11-2011, 05:52 AM   #8
surferdrew
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MaltMonster

You are correct because in order to get sugars from grain, you would have to have them soak (mash) in water within a specific temperature range that a 212F boil is way above. I know that's a crude way of saying it but that's how I understand it.

Specifically, the range is:

Beta Amylase 130 - 150F Produces small, highly fermentable sugars.
Alpha Amylase 155 - 167F Produces larger, less fermentable sugars

 
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Old 03-11-2011, 03:05 PM   #9
dancness
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But the instructions say to steep the grains at 150-160 for 1/2 hour, which is the correct temp to get the sugars out.... am I missing something?

 
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Old 03-12-2011, 05:48 AM   #10
surferdrew
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Quote:
Originally Posted by dancness
But the instructions say to steep the grains at 150-160 for 1/2 hour, which is the correct temp to get the sugars out.... am I missing something?
Hey! Sorry, I was responding to two separate posts at the same time and meant to post this on the other one (related to AG brewing)!



 
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