Gravity Readings with my Brewing Process - Home Brew Forums

 Home Brew Forums > Gravity Readings with my Brewing Process

12-27-2012, 12:51 AM   #1
Scottyh
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Jan 2011
Scottsdale, AZ
Posts: 15

12-27-2012, 01:21 AM   #2
sirmeowsalot
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Apr 2012
gville, FLOrida
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There's a couple of things that could attribute to this that I can think of...
1) the water temp. You said you took a reading pre-boil and I'm assuming post mash then the temp would definitely be a factor. Hydrometers are calibrated to be used at 68 degrees (I could be a couple of degrees off, but its close to there)
2) the boil off. If you boiled off enough water and it became concentrated enough its possible to change the gravity. Although I don't actually know how much water it would mean that you had to boil off.

*insert someones math work here*

Actually, there could be another issue. The crush of the grain, if the crush was to coarse its possible to affect your gravity significantly

12-27-2012, 01:40 AM   #3
Scottyh
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Jan 2011
Scottsdale, AZ
Posts: 15

ok thanks for the reply. Should I be waiting for post mash to cool before taking the gravity reading?

12-27-2012, 03:49 PM   #4
sirmeowsalot
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Apr 2012
gville, FLOrida
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That's what I would recommend, taking the gravity is one of the last things I do before actually transferring to a fermentor.

Upon doing a little research, hydrometers are either calibrated for 68 or 60 degrees (F).

http://www.brewersfriend.com/hydrometer-temp/

It seems like yours is calibrated for 60 degrees. By using the numbers you mentioned and if it was post mash pre boil I imagine the temperature then would have been between 150-160 degrees. So if you type that in for the temp, along with your actually gravity (1.034) you'll notice that in reality your gravity was exactly around what it should have been (1.050-1.055). : )

12-27-2012, 03:55 PM   #5
RM-MN
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Nov 2010
Solway, MN
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Quote:
Right there is the problem. Wort is much denser than water and it is quite difficult to get them to mix properly. You just measured more water than wort. It could have gone the other way too and had you measuring more wort than water and gotten a much higher OG than planned.

12-27-2012, 07:56 PM   #6
WoodlandBrew

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Oct 2012
Malden, MA
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Quote:
 Originally Posted by RM-MN Right there is the problem. Wort is much denser than water and it is quite difficult to get them to mix properly. You just measured more water than wort. It could have gone the other way too and had you measuring more wort than water and gotten a much higher OG than planned.
Stratification can cause some measurement error, but I'm not sure about it causing a 16 point difference in a 1.054 wort. Mr. Wizard from BYO talks about almost this exact topic it in this article:
http://byo.com/stories/wizard/articl...ling-mr-wizard
(scroll down to the second question)

And he's talking about mixing LME with top off water. (LME has a specific gravity of about 1.300)

to quote the wizard:
Quote:
 The variation is typically between 0.1–0.2° Plato or about 0.0004–0.0008 specific gravity units.
Temperature is fairly likely. at 160 degrees the reading will be about 15 points which is what the OP was seeing.
http://www.ebrew.com/primarynews/ct_...correction.htm
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12-28-2012, 05:07 AM   #7
helibrewer

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Nov 2011
Santa Rosa, CA
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Also, make sure your equipment profile in BeerSmith is as accurate as you can get it. All of the volumes use your equipment profile so it needs to be accurate.
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