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Old 12-30-2012, 03:57 AM   #1
Jakeorjacob
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Bought a refractometer a couple months ago and I'm really enjoying using it to measure pre-boil and OG before adding yeast. However, I was very confused to make a couple batches that I thought were under-attenuated because I kept using the refractometer to find the Brix (and then gravity) of the fermenting wort. I had no idea that the calculation for determining the gravity of fermenting wort is a) different and b) complicated.

So, my two questions:

1. What is the calculation?
2. What websites or apps do people use to find a reliable gravity using the Brix and OG of fermenting wort? I've seen a couple but am getting slightly different numbers from each one.

(I understand that I could just measure gravity using a hydrometer, but I am brewing one gallon batches (at least for a little while longer) and I hate to waste that much wort just to check the gravity. The refractometer works so much better and if I can find a reliable way to calculate, I will be a happy camper!)



 
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Old 12-30-2012, 04:03 AM   #2
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Good timing, just went through this very topic in another post.

The website to use seems to be..

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


Here is the post we were discussing the drawbacks of using a refractometer for calculating beer OG and FG.

http://www.homebrewtalk.com/f14/who-...38/index3.html



 
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Old 12-30-2012, 04:22 AM   #3
Jakeorjacob
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Sweet, thanks!

 
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Old 12-30-2012, 04:54 AM   #4
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Just drop the whole hydrometer into the batch instead of taking a sample. Make sure its really clean....!

 
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Old 12-30-2012, 05:01 AM   #5
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I had my refractometer doubts for awhile too, but after comparing a few batches' final gravity with a hydrometer and refractometer using a correction table I've found a refractometer pretty accurate. The two might not agree completely, like 0.003 off. I can live with that and have more beer in the end.

 
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Old 12-30-2012, 05:53 AM   #6
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Quote:
Originally Posted by Dan View Post
I had my refractometer doubts for awhile too, but after comparing a few batches' final gravity with a hydrometer and refractometer using a correction table I've found a refractometer pretty accurate. The two might not agree completely, like 0.003 off. I can live with that and have more beer in the end.
My same conclusion as well.. Had doubts, confirmed those doubts, and the significance of those differences are.. well insignificant in my opinion. Pick one and stick with it.

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Old 12-30-2012, 01:05 PM   #7
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Nice. I like using the refractometer way better, and even if I was making ten gallons, the amount of liquid lost to a hydrometer would still irk me. It's like half a beer! I have no need to "sample" that much beer every time I check the gravity - the few extra drops left over from the refractometer is usually enough to get an idea on how the beer is doing.

 
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Old 12-30-2012, 01:22 PM   #8
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Another post about refractometer accuracy for FG. I'm getting a refractometer anyway.
http://www.homebrewtalk.com/f11/refr...d-beer-333712/
... and from that thread
Quote:
Originally Posted by erikpete18 View Post
Personally, I don't mind using the hydrometer, because its a lot harder to taste test my refractometer samples!
Sock, great idea to put the hydrometer in the wort bucket - if you can read it.
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Old 12-30-2012, 01:35 PM   #9
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I have been just dropping mine into the wort bucket for a while now. Much easier. Refractometer is next on my goodie list.

 
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Old 12-30-2012, 01:53 PM   #10
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I always use a refractometer for prefermentation readings for my beer and wine. Then, for the FG, I use a hydrometer.

I've never had my refractometer be accurate, even with corrections, with a finished beer or wine. Ever.

But I love my refractometer, and I use it several times on each brewday.

I use my hydrometer on the day I package the beer. It doesn't take much beer for a sample- I think it's 3 ounces. I just drink that sample. I can "afford" to give up three ounces of beer with a FG reading to ensure I don't get bottle bombs. It's worth it!


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