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Old 01-29-2013, 03:29 PM   #1
wfowlks
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So for a while now I have been using a refractometer to get the gravity readings of my beer. I like this because the hydrometer typically requires about 8 oz. while a refractometer only requires a few drops. And because I like to take frequent readings... you see the point.

I just did a chocolate stout, and I noticed that after a week it only went down to a BRIX reading of 9, with an OG of 1.052. But I then tasted it and I could taste the alcohol in it. Then I got to thinking that the chocolate powder could be affecting the BRIX reading. I think I may just pull the trigger and do a full hydrometer reading.

But I wanted to see if anyone else could either confirm or refute my theory

 
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Old 01-29-2013, 03:39 PM   #2
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My disclaimer: I am not a professional at this, so take my theory with the understanding that I have only been brewing for less than a year.

It is my understanding that because there is alcohol in the beer after fermentation starts, the refractometer reading is inaccurate and has to be "adjusted" using some calculations.

If I could figure out how to reference a thread that I started on this very topic, Bobby from BrewHardware explained it and gave a reference to a site that could help with adjustments
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Old 01-29-2013, 03:41 PM   #3
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http://www.homebrewtalk.com/f36/refr...stions-380304/

See if this works.
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Old 01-29-2013, 03:42 PM   #4
iaefebs
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Your corrected reading would be 1.025 with a 3.51 ABV. What temperature did you ferment at?

 
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Old 01-29-2013, 03:44 PM   #5
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Yes, the alcohol affects refractometer readings. Check out the work done by Sean Terrill on his site:

http://seanterrill.com/2012/01/06/re...er-calculator/

he also gives a nice explanation of why the formulas and calculators are not accurate with alcohol. I have found his calc to be the most accurate when using a refractometer for final gravity readings and % alc.
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Old 01-29-2013, 03:50 PM   #6
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according to his site your OG in Brix was about 13.5, your FG in Brix of 9 should give you a 1.0198 FG. This may be a little high but for a stout, depnding on the strain. without knowing the strain used and the temps fermented at it is hard to say if the beer is done fermenting. Another week in primary and you should see it come down a bit.
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Old 01-29-2013, 03:52 PM   #7
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the chocolate powder will not affect your readings.
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Old 01-29-2013, 03:53 PM   #8
iaefebs
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Quote:
Originally Posted by BigRedHopHead View Post
according to his site your OG in Brix was about 13.5, your FG in Brix of 9 should give you a 1.0198 FG. This may be a little high but for a stout, depnding on the strain. without knowing the strain used and the temps fermented at it is hard to say if the beer is done fermenting. Another week in primary and you should see it come down a bit.
You need to go back to the OP post. He started at 1.052 and has a current brix of 9. The conversion to SG makes it 1.025.

 
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Old 01-29-2013, 04:36 PM   #9
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The temp was about 63, the optimum temperature for the yeast I was using is 65-68 (WLP004). I did do a starter so that I could split the 1 vial into the 2 5 gallon batches that I had. I also just acquired a heater so that I can keep the temp at about 66 degrees. And I will see if that helps.

Thanks for the info on the chocolate powder. I have done the refractometer readings before, I use the beersmith tool. But I just wasn't sure if the chocolate would affect it, because the refractometer is just a measure of how much light it lets through.

 
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Old 01-29-2013, 07:06 PM   #10
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Quote:
Originally Posted by iaefebs View Post
You need to go back to the OP post. He started at 1.052 and has a current brix of 9. The conversion to SG makes it 1.025.
Only if you use an old, inaccurate calculator.
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