Author Topic: Improved Refractometer Correction calculator  (Read 7867 times)

Offline Robert

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Re: Improved Refractometer Correction calculator
« Reply #105 on: February 08, 2018, 01:16:32 AM »
My hydrometer doesnt make my head hurt like this.  But nothing makes my head hurt like something that seems like it should be straightforward, but you just can't find a clear answer in all the information out there! Or even whether sources are using terms consistently.
Rob Stein
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Offline Big Monk

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Re: Improved Refractometer Correction calculator
« Reply #106 on: February 08, 2018, 01:19:48 AM »
My hydrometer doesnt make my head hurt like this.  But nothing makes my head hurt like something that seems like it should be straightforward, but you just can't find a clear answer in all the information out there! Or even whether sources are using terms consistently.

It’s really simple: determine your units correction factor and you are good to go.
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Offline klickitat jim

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Re: Improved Refractometer Correction calculator
« Reply #107 on: February 08, 2018, 01:22:01 AM »
What's more, there is going to be a different correction factor for each gravity. That's why we do so many test samples, to determine the average correction factor.

The end result difference between a 1.04 and 1.02 is quite minimal. Nothing to get in a twist about.

If you recall, I was cautioned about using my outliers. Well the difference in the final results between with outliers or without is like 1/2 of a gravity point in a moderate beer
« Last Edit: February 08, 2018, 01:25:45 AM by klickitat jim »

Offline Robert

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Re: Improved Refractometer Correction calculator
« Reply #108 on: February 08, 2018, 01:27:17 AM »
That was the problem.  My tests were all over the place (consistent w/in gravity, erratic between gravities)  so I don't see a factor for my unit I can trust.  I can't get my head around why an average would be valid when the apparent correction did not skew along a smooth curve or line as gravity increased:  just bounced around.  So I couldn't call anything an outlier, there was just no pattern.

EDIT And how, anyway, could I trust that a given reading on a given brew day was not itself an outlier?
« Last Edit: February 08, 2018, 01:31:25 AM by Robert »
Rob Stein
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Offline Big Monk

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Re: Improved Refractometer Correction calculator
« Reply #109 on: February 08, 2018, 01:41:42 AM »
Here is the way we do it and why I feel, empirically that it works:

1.) We calculate a “target” first wort gravity using Kai’s idealized equation, i.e. 100% Mash Efficiency, 80% DBFG, and 4% moisture. This gives you the maximum theoretically possible first wort gravity. Since we assume no-sparge this is the maximum theoretical pre-boil gravity.

2.) We then calculate the “estimated” first wort gravity by subbing actual malt parameters and mash efficiency into Kai’s equation. We know that this will deviate from the “target” as mash tun Losses and absorption increases and converge with the “target” with less loss and smaller grain bills. 

3.) We use a static value for Refractometer correction and always measure very close to our estimates, so it must be nothing if not consistent.

One caveat though: We (the royal We as in many of us at LOB forum) are in a pretty tight gravity range. Even me, who only brews Trappist “style” ales, stay pretty moderate on wort gravity and supplement with sugar.
“We are what we repeatedly do. Excellence, therefore, is not an act, but a habit.” Aristotle

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Offline klickitat jim

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Re: Improved Refractometer Correction calculator
« Reply #110 on: February 08, 2018, 01:44:25 AM »
That was the problem.  My tests were all over the place (consistent w/in gravity, erratic between gravities)  so I don't see a factor for my unit I can trust.  I can't get my head around why an average would be valid when the apparent correction did not skew along a smooth curve or line as gravity increased:  just bounced around.  So I couldn't call anything an outlier, there was just no pattern.

EDIT And how, anyway, could I trust that a given reading on a given brew day was not itself an outlier?
Near as I can figure, my variations are largely due to my ability to read the hydrometer. I suspect that if I used an easier to read precision hydrometer the swing would tighten. To me it's fine. I can't tell, by looking at my hydrometer in wort, the difference between 1.060 and 1.0605... I also have no way of knowing if suspended solids are effecting the hydrometer. So there is still a degree of trust involved if all you use is a hydrometer.

All good folks. I don't sell refractometers, lol

Offline Robert

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Re: Improved Refractometer Correction calculator
« Reply #111 on: February 08, 2018, 01:52:44 AM »
I guess I'll stick with my hydro (again as I sparge, I use iodine to confirm conversion in the tun anyway), but over time I may occasionally take a refracto reading on occasion and see if it's consistent in normal wort range. Just for fun, if I can remember. I have a hydro that even my crappy old eyes can read the 0.0005 lines on (actually 3 narrow range hydrometers), and I don't use it on mash, only wort, so floaties aren't a factor.  And I don't sell hydrometers either!
Rob Stein
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Offline Robert

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Re: Improved Refractometer Correction calculator
« Reply #112 on: February 08, 2018, 08:02:42 PM »
UPDATE AND APOLOGY FOR QUESTIONING  YOU GUYS' METHODS

So I had some time today.  Thought about some methodology you guys suggested.  Got out the stir plate, used Jim's method, and did a MUCH more extensive series of tests.  I also remembered that Jim thought that a lack of homogeneity might show up big time in the refractometer sample, so I took those readings FIRST right out of the beaker on the stir plate and THEN checked with the hydrometer.  Well! 

Result:  very consistent for the most part, and even the apparent outliers, when included in an average of all tests, fall precisely in line with the result excluding them.  I get a correction factor of 0.97, which, having gone through this, I accept.  I will now trust the refractometer enough for on-the-fly assessment of wort in the mash and boil.  But I'm still sticking with my precision hydrometers for OG and beyond.

Big Monk, Jim, guys, thanks for helping me get my head around this! 
« Last Edit: February 09, 2018, 12:11:42 AM by Robert »
Rob Stein
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Offline klickitat jim

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Re: Improved Refractometer Correction calculator
« Reply #113 on: February 08, 2018, 08:15:26 PM »
There ya go. Cool

Offline klickitat jim

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Re: Improved Refractometer Correction calculator
« Reply #114 on: February 08, 2018, 08:19:21 PM »
Another test i want to do is hydrometer in distilled water at calibrated temp, compared to the same water with a obviously visible amout of yeast in suspension. Palmer claims starch is suspension threw his off by 10 points. I hope to not ever have visibly starch in mine, but occasionally there's visible yeast.

Offline dmtaylor

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Re: Improved Refractometer Correction calculator
« Reply #115 on: February 08, 2018, 08:20:45 PM »
I'd be very very interested to hear anyone's results for FG using the refractometer, once they know their correction factor.  Use the "Old Cubic" or the OP's calculator, and watch just how close you come.  You may find as I have that the refractometer is every bit as useful for FG as it is for OG.

Cheers all.
Dave

The world will become a much more pleasant place to live when each and every one of us realizes that we are all idiots.

Offline Robert

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Re: Improved Refractometer Correction calculator
« Reply #116 on: February 08, 2018, 08:31:28 PM »
Another test i want to do is hydrometer in distilled water at calibrated temp, compared to the same water with a obviously visible amout of yeast in suspension. Palmer claims starch is suspension threw his off by 10 points. I hope to not ever have visibly starch in mine, but occasionally there's visible yeast.
10 points sounds like a lot, but I know mine often has dropped (apparently) about 1 point pre- to post- cold crash.  I never know whether that's a change in suspended yeast, or just in bubbles lifting the hydrometer,or the temperature fudge factor. I guess at that point there's not a huge amount of yeast still in suspension anyway.  Either way, I just assume the accurate FG is the post crash.  (In fact I don't even do the pre crash anymore, but that's to avoid opening the carboy now that I'm hyper  cold side O2 conscious!  In fact I don't see a need for any gravity readings but OG and FG taken after the fact.  And the only reason for that is, if attenuation was off, I'd reculture instead of repitching. I know my yeast.) Anywho, if you do the experiment I'll be curious to see the post!
Rob Stein
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I'd rather have questions I can't answer than answers I can't question.

Offline Big Monk

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Re: Improved Refractometer Correction calculator
« Reply #117 on: February 08, 2018, 08:32:44 PM »
I'd be very very interested to hear anyone's results for FG using the refractometer, once they know their correction factor.  Use the "Old Cubic" or the OP's calculator, and watch just how close you come.  You may find as I have that the refractometer is every bit as useful for FG as it is for OG.

Cheers all.

I have the "New Cubic" and "New Linear" calculations coded into our spreadsheet on a toggle. "New Cubic"is the one I've gotten the best results from. "Old Cubic" always seems low to me.
“We are what we repeatedly do. Excellence, therefore, is not an act, but a habit.” Aristotle

"Messieurs, c’est les microbes qui auront le dernier mot." Louis Pasteur

Check us out at www.lowoxygenbrewing.com

Offline Robert

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Re: Improved Refractometer Correction calculator
« Reply #118 on: February 08, 2018, 08:41:49 PM »
I'd be very very interested to hear anyone's results for FG using the refractometer, once they know their correction factor.  Use the "Old Cubic" or the OP's calculator, and watch just how close you come.  You may find as I have that the refractometer is every bit as useful for FG as it is for OG.

Cheers all.
I just signed up to use the OP's calculator.  I'll report here!
Rob Stein
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I'd rather have questions I can't answer than answers I can't question.

Offline dmtaylor

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Re: Improved Refractometer Correction calculator
« Reply #119 on: February 08, 2018, 08:51:30 PM »
I'd be very very interested to hear anyone's results for FG using the refractometer, once they know their correction factor.  Use the "Old Cubic" or the OP's calculator, and watch just how close you come.  You may find as I have that the refractometer is every bit as useful for FG as it is for OG.

Cheers all.
I just signed up to use the OP's calculator.  I'll report here!

...And we're officially back on-topic!  ;D  8)
Dave

The world will become a much more pleasant place to live when each and every one of us realizes that we are all idiots.