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Old 01-30-2013, 11:59 PM   #1
Nov 2011
Kingston, Pennsylvania
Posts: 314
Liked 16 Times on 14 Posts

I got a refractometer for Christmas and was doing some reading to find out that gravity readings of fermented wort are nearly useless without conversion charts. Found this out the hard way after I was baffled my beer was still at 1.029 (refractometer reading) after nearly two weeks, so grab the hydrometer and found my gravity was much lower and finished right around where i should be at around 1.011.

Anyway, the question I'm trying to get at is: yes, the gravity reading is WAY off from what it should be with the refractometer, but can I take gravity readings with the refractometer to see if the gravity is stable? That is, if I read the same reading with the refractometer over 3 days is this a reliable measurement to know that its done fermenting?

Its much easier and less wasteful to draw a small (inaccurate) sample then to draw a bigger sample to get an accurate reading. I could always check the gravity when I get it out of the carboy to get a stable reading with the hydrometer for FG, right?
This is grain, which any fool can eat, but for which the Lord intended a more divine means of consumption... Beer!

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Old 01-31-2013, 12:17 AM   #2
Jan 2008
Delaware, OH
Posts: 91
Liked 5 Times on 5 Posts

A refractometer would work great for that purpose. The reason the readings are skewed after fermentation is because of the presence of alcohol, the reading will be stable just not accurate and thats why you need to use a correction chart or calculator to get the accurate gravity reading.

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Old 01-31-2013, 12:24 AM   #3
b-boy's Avatar
Jun 2011
The Frozen Tundra, NY
Posts: 4,393
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There are plenty of online calculators. All you need is OG and your current gravity. It'll do the calculation for you. I don't think the final value is 100% perfect, but for my needs it's fine. I'll take a refractometer any day.
Never underestimate the potential of someone who refuses to act their age.

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Old 01-31-2013, 02:31 AM   #4
helibrewer's Avatar
Nov 2011
Santa Rosa, CA
Posts: 3,813
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+1 on all of these...exactly what I do. If I remember I take a hydro when I keg just to annotate my notes...up to that point it's all refractometer with a correction.

I think BeerSmith will let you calibrate their tool by taking a simultaneous hydro and refract reading and entering both builds the correction factor from that.
Something is always fermenting....
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