Author Topic: Improved Refractometer Correction calculator  (Read 12691 times)

Offline Petr

  • 1st Kit
  • *
  • Posts: 13
Re: Improved Refractometer Correction calculator
« Reply #195 on: March 11, 2018, 11:36:37 PM »
This is crazy.  We're all getting different answers.  Novotny and Old Cubic are most accurate for mine all the way across.

Been thinking about this whole thing.

I suspect a source of difficulty is the assumption being made that the only difference to account for between wort and beer is the presence of alcohol. In fact of course many other fermentation products are present (CO2 can be ignored as it is expressed from under the cover plate of the refractometer. )

The more I test, the more I find different formulae working at different times and in different batches.  The differences between the beers are seemingly minor and various:   slight variations in the blend of malts, amounts and varieties of hops used, attenuation limit, generation and pitch rate of the yeast, and so on.  (You know, always dialing in the recipe!)  But each of these factors could have a significant effect on the chemical composition of the fermenting/fermented beer, and I suspect in turn a significant effect on the refractivity index.   So every beer, or at least every set of samples produced identically, would really require its own correction formula.  And that formula could only be modeled retroactively once you already have a full analyses of the beer, and so would be superfluous.

  Refractivity and density just don't correlate except as determined for a specific substance.

Yes, beer is a mixture of thousands of compounds but when compared to residual sugar, water and ethanol everything is negligible in terms of concentrations, their concentrations are a couple of order magnitudes lower than that "big three". Refractive index is concentration sensitive, thus small differences in concentrations of those "other" compounds do not have a significant effect on the measurement at our level of accuracy.

Every equation assumes some sort of balance between consumed sugar and produced ethanol. If the equation does not work precisely that simply means that particular beer does not follow the assumed balance. The balance can be theoretical or experimentally build in the equation - but it is always there. That is something that Balling figured it out in 1865 since then his equation is kind of golden standard although deviations from his balance/equation are known.
« Last Edit: March 11, 2018, 11:45:32 PM by Petr »

Offline klickitat jim

  • I must live here
  • **********
  • Posts: 8604
Re: Improved Refractometer Correction calculator
« Reply #196 on: March 12, 2018, 05:12:25 AM »
I'm really enjoying my switch to refractometer only. But I think it works so well for me because I only care about 'close enough'. I'm actually considering picking up a Hannah digital next fall, just for fun. I read Marshall's review of it, and saw that when he tested final Plato with it he used Sean's 1.040 correction factor. My first thought was OMG! He should have read this thread. But for kicks I plugged in some arbitrary numbers. If the refractometer read 18 brix starting and 8 brix final, with a correction factor of 1 the actual FG is 1.013. If the correction factor was 1.0126 (mine) it finished at 1.012. If the correction factor was 1.04 the FG is 1.012. The 3 different correction factors end up covering a pretty narrow span between a total of .2% abv. I am so grateful that to me, that is totally close enough. But, I don't spund.

For now, my $12 Chinese refractometer is getting the job done. I have not touched my hydrometer in a couple months. I probably will treat myself to the $180 digital toy in the fall. I won't need to fumble with the tiny screw driver, or trying to line up my bifocals on the eyepiece. Just push a button and enter the number to my correction app.

For folks who don't spund, but still freak out about precision, I have a challenge for you. The next time you drink a commercial beer, one you don't know the numbers on, guess what the FG is. Write it down so you can't cheat. Then measure it. If you can't consistently and accurately taste the FG within +/- 1 gravity point, why does it really matter what your instruments and math says?
« Last Edit: March 12, 2018, 05:28:57 AM by klickitat jim »

Offline Slowbrew

  • Brewmaster General
  • *******
  • Posts: 2495
  • The Slowly Losing IT Brewery in Urbandale, IA
Re: Improved Refractometer Correction calculator
« Reply #197 on: March 12, 2018, 11:09:50 AM »
Jim is man with my own view of the world.  I too haven't used my hydrometer in years.  My refractometer gets me "close enough" and for me that's good enough.  I don't have to file federal paperwork or worry about audits so if my kegs don't explode, I'm happy.

Everyone's views have been interesting and informative but for me the need for perfection just isn't there.

Thanks Jim!

Paul
Where the heck are we going?  And what's with this hand basket?

Offline klickitat jim

  • I must live here
  • **********
  • Posts: 8604
Re: Improved Refractometer Correction calculator
« Reply #198 on: March 12, 2018, 11:32:49 AM »
The last sentence of my "challenge" is worded as a question, not to be a smartie pants (well, maybe a little) but because it's entirely possible that I'm oblivious to why absolute accuracy is necessary.

Offline dmtaylor

  • Official Poobah of No Life.
  • *
  • Posts: 3657
    • Manty Malters - Meet the Malters! - Dave Taylor
Re: Improved Refractometer Correction calculator
« Reply #199 on: March 12, 2018, 12:08:51 PM »
I have a challenge for you. The next time you drink a commercial beer, one you don't know the numbers on, guess what the FG is. Write it down so you can't cheat. Then measure it. If you can't consistently and accurately taste the FG within +/- 1 gravity point, why does it really matter what your instruments and math says?

Yeah baby!!   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.

Offline Big Monk

  • Brewmaster
  • *****
  • Posts: 681
  • I’m Derek Scott. I’m a Category 26 kind of guy.
    • Low Oxygen Brewing
Re: Improved Refractometer Correction calculator
« Reply #200 on: March 12, 2018, 12:24:14 PM »
The last sentence of my "challenge" is worded as a question, not to be a smartie pants (well, maybe a little) but because it's entirely possible that I'm oblivious to why absolute accuracy is necessary.

I bottle with extract which is pretty much the only reason I care about accuracy. Unlike my keg Spunding brethren, I can’t bleed pressure once bottled.

I can’t see why anyone else would want to freak out.
“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 out The Brewing Troubleshooters at https://brewingtroubleshooter.yolasite.com/

Offline dmtaylor

  • Official Poobah of No Life.
  • *
  • Posts: 3657
    • Manty Malters - Meet the Malters! - Dave Taylor
Re: Improved Refractometer Correction calculator
« Reply #201 on: March 12, 2018, 12:34:15 PM »
The last sentence of my "challenge" is worded as a question, not to be a smartie pants (well, maybe a little) but because it's entirely possible that I'm oblivious to why absolute accuracy is necessary.

I bottle with extract which is pretty much the only reason I care about accuracy. Unlike my keg Spunding brethren, I can’t bleed pressure once bottled.

I can’t see why anyone else would want to freak out.

The only reason I get in this deep is due to my love for math and science.  But the more I sit back and think about it, the more I realize how much of an unnecessary expediture of time it all really is.

That said... ability to match within 0.001 of a hydro now is a mission accomplished, for me, here, using my cheap junk refractometer.  Yay.
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 Big Monk

  • Brewmaster
  • *****
  • Posts: 681
  • I’m Derek Scott. I’m a Category 26 kind of guy.
    • Low Oxygen Brewing
Re: Improved Refractometer Correction calculator
« Reply #202 on: March 12, 2018, 12:50:45 PM »
The last sentence of my "challenge" is worded as a question, not to be a smartie pants (well, maybe a little) but because it's entirely possible that I'm oblivious to why absolute accuracy is necessary.

I bottle with extract which is pretty much the only reason I care about accuracy. Unlike my keg Spunding brethren, I can’t bleed pressure once bottled.

I can’t see why anyone else would want to freak out.

The only reason I get in this deep is due to my love for math and science.  But the more I sit back and think about it, the more I realize how much of an unnecessary expediture of time it all really is.

That said... ability to match within 0.001 of a hydro now is a mission accomplished, for me, here, using my cheap junk refractometer.  Yay.

I’ve actually come up with a really slick way of getting all the info I need in one fell swoop.

Since I test the base malts I buy for DI pH, I can make the test mash to the same gravity as the batch and get my correction factor for the batch at the outset.
“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 out The Brewing Troubleshooters at https://brewingtroubleshooter.yolasite.com/

Offline Robert

  • Official Poobah of No Life.
  • *
  • Posts: 3746
Re: Improved Refractometer Correction calculator
« Reply #203 on: March 12, 2018, 01:05:14 PM »
I did some deep diving on the interewebs this weekend, mostly threads on other forums (many I never knew existed) and some of the sources they led to.  Turns out there's a good amount of research confirming my suspicions above about many factors confounding corrections.  It seems hops alone can have an effect nearly as significant as alcohol, as can different grists, let alone all the other compounds in beer.  Much more research would be needed if it's even possible to develop reliable corrections, and the pros aren't going to do it, they don't use refractometers. We're just trying to use an instrument to measure something it wasn't designed to measure. (No I don't have all the references, you've got Google if you care.)

This looked good to me on a limited number of samples, but the more I've racked up, it looks like none of these formulas really works, which now doesn't surprise me.  If I have all the formulas in front of me (and thanks to Big Monk, I do!) I can find one of the half dozen that's fairly close.  But that just means that there's a one in six chance I can squint really hard and pretend it looks like something's working, not that it is.

So for my part, I'm back to the position that refractometers are useful pre-boil only, and I establish a correction factor for each individual batch using the saccharometer OG.  Even Terrill has said (referenced somewhere in this thread) that if you actually want to know FG (or for that matter when to spund) you really need a hydrometer.

So finally, if you're of the school of "close enough is close enough, I  don't  really need to know," why do you need any instrument at all?

  When it stops bubbling, its done!
Rob Stein
Akron, Ohio

I'd rather have questions I can't answer than answers I can't question.

Offline Petr

  • 1st Kit
  • *
  • Posts: 13
Re: Improved Refractometer Correction calculator
« Reply #204 on: March 12, 2018, 03:00:31 PM »
I did some deep diving on the interewebs this weekend, mostly threads on other forums (many I never knew existed) and some of the sources they led to.  Turns out there's a good amount of research confirming my suspicions above about many factors confounding corrections.  It seems hops alone can have an effect nearly as significant as alcohol, as can different grists, let alone all the other compounds in beer.  Much more research would be needed if it's even possible to develop reliable corrections, and the pros aren't going to do it, they don't use refractometers. We're just trying to use an instrument to measure something it wasn't designed to measure. (No I don't have all the references, you've got Google if you care.)

This looked good to me on a limited number of samples, but the more I've racked up, it looks like none of these formulas really works, which now doesn't surprise me.  If I have all the formulas in front of me (and thanks to Big Monk, I do!) I can find one of the half dozen that's fairly close.  But that just means that there's a one in six chance I can squint really hard and pretend it looks like something's working, not that it is.

So for my part, I'm back to the position that refractometers are useful pre-boil only, and I establish a correction factor for each individual batch using the saccharometer OG.  Even Terrill has said (referenced somewhere in this thread) that if you actually want to know FG (or for that matter when to spund) you really need a hydrometer.

So finally, if you're of the school of "close enough is close enough, I  don't  really need to know," why do you need any instrument at all?

  When it stops bubbling, its done!

I highly doubt that hop compounds can have a comparable effect on refractive index as alcohol that is just not possible from the chemistry point of view when hop compounds are there in ppm level and alcohol in a couple of %. Can you provide me with a work that you were referring to? I did my google research but didn't find anything close to that statement.

I'm normally just fine with +- 0.002 accuracy of FG, and for a long time now I use refractometer only. The main reason why I bothered with the new formula wasn't actually FG because for that purpose with reasonable accuracy you can use Terill's formula just fine. The reason was that sometimes I need also a reading during fermentation and don't want to waste about 100 mL of wort every time, especially if it is an experimental brew with total volume 2 litres and often less... The thing is that my formula works for wort during the whole fermentation and that is the main advantage of it. I know that not everyone is in need of measurements during fermentation but the option is there for those who need or/and want.

If you don't care about the FG at all then well no problem with that neither. It's up to every one of us.

« Last Edit: March 12, 2018, 03:09:48 PM by Petr »

Offline Robert

  • Official Poobah of No Life.
  • *
  • Posts: 3746
Re: Improved Refractometer Correction calculator
« Reply #205 on: March 12, 2018, 03:46:04 PM »
Sorry, I didn't save my search results.  I just kept reading until I was assured there really is something going on here to confirm my suspicions.  I think all the non-alcohol factors, in the aggregate, can have enough impact that a formula based on one set of samples will not apply universally.  But if you are only interested in a certain margin of accuracy, I'm sure you can establish a correlation that works for you.  This really doesn't bother me, I just plan my brew length with a spare liter or so to allow for all the samples I might want to pull.  I realize this is not feasible for small batch brewers. I don't really have skin in this game. The amount of discrepancy between formulae,  each of which was empirically derived, just bothered me.  I wanted some insight.  Now everyone should just do what works for them!
Rob Stein
Akron, Ohio

I'd rather have questions I can't answer than answers I can't question.

Offline narvin

  • Brewmaster General
  • *******
  • Posts: 2286
  • Baltimore
Re: Improved Refractometer Correction calculator
« Reply #206 on: March 12, 2018, 03:58:02 PM »
On the flipside, what makes us think that density is a good measure of how the beer will taste?  It is well known that different sugars taste vastly different in a finished beer, so one 1.015 beer can taste sweet and another not at all.  Add alcohol into the density equation and you aren't even measuring one thing, but a balance - hence "apparent attenuation".  So, other than knowing when your beer is done, what is it really telling you?

I've been measuring with refractometer only for a while, and it tells me just as much about the final mouthfeel of a beer as density ever did.  It also helps to measure a variety of beer (commercial, other homebrews) and get an idea of what your target is for the style.  It's like going from F to C: you're never going to make the switch if you're constantly doing conversions in your head.  Think native!
Please do not reply if your[sic] an evil alien!
Thanks

Offline Robert

  • Official Poobah of No Life.
  • *
  • Posts: 3746
Re: Improved Refractometer Correction calculator
« Reply #207 on: March 12, 2018, 04:11:59 PM »
I'm only interested in a reasonably accurate reading so I could spot any change in performance that would tell me not to repitch the yeast.  Otherwise, like I said, when it stops bubbling, its done!
Rob Stein
Akron, Ohio

I'd rather have questions I can't answer than answers I can't question.

Offline klickitat jim

  • I must live here
  • **********
  • Posts: 8604
Re: Improved Refractometer Correction calculator
« Reply #208 on: March 12, 2018, 04:17:10 PM »
I did some deep diving on the interewebs this weekend, mostly threads on other forums (many I never knew existed) and some of the sources they led to.  Turns out there's a good amount of research confirming my suspicions above about many factors confounding corrections.  It seems hops alone can have an effect nearly as significant as alcohol, as can different grists, let alone all the other compounds in beer.  Much more research would be needed if it's even possible to develop reliable corrections, and the pros aren't going to do it, they don't use refractometers. We're just trying to use an instrument to measure something it wasn't designed to measure. (No I don't have all the references, you've got Google if you care.)

This looked good to me on a limited number of samples, but the more I've racked up, it looks like none of these formulas really works, which now doesn't surprise me.  If I have all the formulas in front of me (and thanks to Big Monk, I do!) I can find one of the half dozen that's fairly close.  But that just means that there's a one in six chance I can squint really hard and pretend it looks like something's working, not that it is.

So for my part, I'm back to the position that refractometers are useful pre-boil only, and I establish a correction factor for each individual batch using the saccharometer OG.  Even Terrill has said (referenced somewhere in this thread) that if you actually want to know FG (or for that matter when to spund) you really need a hydrometer.

So finally, if you're of the school of "close enough is close enough, I  don't  really need to know," why do you need any instrument at all?

  When it stops bubbling, its done!
Robert, bubbling or lack of bubbling is not reliable. Getting two readings, days apart, which are the same... much more reliable way to determine it's done. What I'm talking about as "close enough" is whether it's 1.012 SG or 1.013 SG terminal.

Offline Robert

  • Official Poobah of No Life.
  • *
  • Posts: 3746
Re: Improved Refractometer Correction calculator
« Reply #209 on: March 12, 2018, 04:34:24 PM »
Sorry, I was using "bubbling" rather loosely and maybe being a little bit facetious.  What I mean is, when there is no sign of active fermentation, which you can determine any way you like.  I largely rely on time, knowing how long it takes my yeast to do the job.  Guess that's pretty much in the "close enough" school.

EDIT  I'm usually right on using time and temp, always within 0.2°P, which will finish out in lagering.  I'd have to be tighter if I bottled!
« Last Edit: March 12, 2018, 04:54:59 PM by Robert »
Rob Stein
Akron, Ohio

I'd rather have questions I can't answer than answers I can't question.