Author Topic: me no understand refractometer correction....  (Read 2537 times)

Offline majorvices

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me no understand refractometer correction....
« on: January 24, 2010, 08:33:32 AM »
So, using the hydrometer correction calculator found here: http://www.onebeer.net/refractometer.shtml gives me incorrect results. For instance, when I type in my original brix (12) and my final brix (5) the reading says says my final gravity is 1.002 .... however, the OG was ~1.050 and the FG is around 1.012 according my correctly calibrated hydromter (the refractometer is also correctly calibrated) ... so what's going on? Is that calculator off or WTF?
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Offline tom

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Re: me no understand refractometer correction....
« Reply #1 on: January 24, 2010, 09:16:04 AM »
What was the final gravity reading of the refractometer?
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Re: me no understand refractometer correction....
« Reply #2 on: January 24, 2010, 09:18:31 AM »
In my experience, the correlation becomes less reliable the further you get from "normal" gravity and attenuation. At 1.050 and 76%, I don't think that's your problem though. I think high concentrations of dissolved gases also throw off the refractive index, so if fermentation is active that could be a factor. It tends to RAISE the Brix reading though, IME. 5°Bx is very low.
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Re: me no understand refractometer correction....
« Reply #3 on: January 24, 2010, 09:19:34 AM »
What was the final gravity reading of the refractometer?
my original brix (12) and my final brix (5)
;)
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Offline tom

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Re: me no understand refractometer correction....
« Reply #4 on: January 24, 2010, 10:36:22 AM »
Just checking!

ProMash gives the same results.
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Offline majorvices

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Re: me no understand refractometer correction....
« Reply #5 on: January 24, 2010, 10:49:09 AM »
could it simply be yeast in suspension skewing the results? Its fairly cloudy and, come to think of it, my IPA was pretty cloudy too and I got the wrong result.
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Re: me no understand refractometer correction....
« Reply #6 on: January 24, 2010, 11:15:01 AM »
Suspended solids shouldn't have any impact on the RI. A cloudy sample makes it hard to read the line accurately. I don't think you could get a ~2°Bx discrepancy from that though.

Things like this are why I went back to using a hydrometer for all FG readings.
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Offline blatz

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Re: me no understand refractometer correction....
« Reply #7 on: January 24, 2010, 11:45:40 AM »
see, its odd, my refracto is always spot on (after correction) with the hydro sample (I still take the hydro on occasion cause I like to taste how things are coming along  ;D )

Don't know what to tell you  :(
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Re: me no understand refractometer correction....
« Reply #8 on: January 24, 2010, 01:35:17 PM »
Hey blatz, I've been doing both to try to get some data points. Once I have 10 or so I'll let you know and hopefully we can compare notes.
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Offline weazletoe

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Re: me no understand refractometer correction....
« Reply #9 on: January 25, 2010, 05:36:32 PM »
Here's what you need to do Major. You have a pickup truck, right? (if not you can borrow mine) Take your refracto, and drive over it several times with your truck. Once I did this with mine, and went back to my hydrometer, I had no more issues with it.  ;D
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Offline denny

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Re: me no understand refractometer correction....
« Reply #10 on: January 25, 2010, 05:57:34 PM »
BRILLIANT!
Life begins at 60.....1.060, that is!

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Offline Thirsty_Monk

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Re: me no understand refractometer correction....
« Reply #11 on: January 25, 2010, 06:06:21 PM »
Back to basic!!!  ;D
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Offline blatz

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Re: me no understand refractometer correction....
« Reply #12 on: January 25, 2010, 07:32:47 PM »
I can't understand how you guys can't get a simple tool to work.

I've helped 2 other guys in my club acquire a refracto, set them up with the correction formulae and they are fine.

There is a thing called 'user error'  ;) ;D
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Offline bluesman

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Re: me no understand refractometer correction....
« Reply #13 on: January 25, 2010, 08:19:08 PM »
We call it "operator error".  ;D  Just kidding.

I like to use my refractometer during the mash and pre-fermentation because it's quick and easy. However, I always use my hydrometer post fermentation because it's most accurate and reliable at that point in the process.

I haven't had any success using a refractometer post fermentation as you are also experiencing. Maybe there's something we are missing, but I like to use my hydrometer because it's dual purpose. I can quantify the result by measuring the gravity and qualify the result by tasting the beer from the hydrometer tube. 
Ron Price

Offline rabid_dingo

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Re: me no understand refractometer correction....
« Reply #14 on: January 26, 2010, 09:34:34 AM »
Another
Here's what you need to do Major. You have a pickup truck, right? (if not you can borrow mine) Take your refracto, and drive over it several times with your truck. Once I did this with mine, and went back to my hydrometer, I had no more issues with it.  ;D

Oh Snap! I really did laugh out loud...
Ruben * Colorado :)