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General Category => Equipment and Software => Topic started by: majorvices on January 24, 2010, 03:33:32 PM

Title: me no understand refractometer correction....
Post by: majorvices on January 24, 2010, 03:33:32 PM
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?
Title: Re: me no understand refractometer correction....
Post by: tom on January 24, 2010, 04:16:04 PM
What was the final gravity reading of the refractometer?
Title: Re: me no understand refractometer correction....
Post by: a10t2 on January 24, 2010, 04:18:31 PM
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.
Title: Re: me no understand refractometer correction....
Post by: a10t2 on January 24, 2010, 04:19:34 PM
What was the final gravity reading of the refractometer?
my original brix (12) and my final brix (5)
;)
Title: Re: me no understand refractometer correction....
Post by: tom on January 24, 2010, 05:36:22 PM
Just checking!

ProMash gives the same results.
Title: Re: me no understand refractometer correction....
Post by: majorvices on January 24, 2010, 05:49:09 PM
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.
Title: Re: me no understand refractometer correction....
Post by: a10t2 on January 24, 2010, 06:15:01 PM
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.
Title: Re: me no understand refractometer correction....
Post by: blatz on January 24, 2010, 06:45:40 PM
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  :(
Title: Re: me no understand refractometer correction....
Post by: a10t2 on January 24, 2010, 08:35:17 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.
Title: Re: me no understand refractometer correction....
Post by: weazletoe on January 26, 2010, 12:36:32 AM
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
Title: Re: me no understand refractometer correction....
Post by: denny on January 26, 2010, 12:57:34 AM
BRILLIANT!
Title: Re: me no understand refractometer correction....
Post by: Thirsty_Monk on January 26, 2010, 01:06:21 AM
Back to basic!!!  ;D
Title: Re: me no understand refractometer correction....
Post by: blatz on January 26, 2010, 02:32:47 AM
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
Title: Re: me no understand refractometer correction....
Post by: bluesman on January 26, 2010, 03:19:08 AM
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. 
Title: Re: me no understand refractometer correction....
Post by: rabid_dingo on January 26, 2010, 04:34:34 PM
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...
Title: Re: me no understand refractometer correction....
Post by: schristian619 on January 26, 2010, 04:43:20 PM
I use the refractometer correction spreadsheet from morebeer.  I can't remember where I got the link to it though.  It has worked for me and I have checked it several times against my hydrometer and its always spot on.  I can't remember the last time I used my hydrometer, except random double checking of the spreadsheet.