Author Topic: other methods of taking gravity readings  (Read 1266 times)

Offline Robert

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Re: other methods of taking gravity readings
« Reply #15 on: April 12, 2019, 01:31:10 AM »
The most accurate formula for me is "Old Cubic", by a hair.  But I did steal and customize Mr. Terrill's spreadsheet and for that I am very thankful.   8)
Could be that's the one that worked better for me, don't recall.*  For a long series of batches I compared (thanks to a spreadsheet Big Monk shared) all of Sean's and Petr's formulas.   I recall that the biggest differences were during fermentation,  and they all converged towards FG.   I've got Petr's, as published in Zymurgy, in my own spreadsheet, and it does very well all along. 

Most importantly, I've proved to myself that a good refractometer can actually be more accurate, in my experience, than a floaty thing.  Especially now I've got the digital unit, thus finally removing the idiot entirely from the process.  ;) 

And anyone who remembers a monster thread from some time ago may recall that I was a serious skeptic of the possibility that refractometers could be of any use in brewing.  My conversion is now complete.

*EDIT  Yep, ran some records through.  "Old cubic" gives me virtually the same FG results as Petr's as published in Zymurgy (also used by Brewer's Friend) gives, which I've confirmed by saccharometer.
« Last Edit: April 12, 2019, 02:18:23 AM by Robert »
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Offline KellerBrauer

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Re: other methods of taking gravity readings
« Reply #16 on: April 12, 2019, 12:11:53 PM »
Even though you need a lot of wort to check gravity using a hydrometer and a sample tube, the wort can be dumped back into the boil kettle with no ill effects. 

Wait - you're taking readings of hot wort?  Ive never heard of doing that - is it somehow telling you the efficiency of the wort?  Doesnt the temperature change the reading? 

I have a thief too, but the amount of wort still is too much for me.  I drink it also, it doesnt go to waste, just wish there was a better way....

Yes, I take reading of the boiling wort throughout the entire 60-90-whatever period.  When doing so, I use both my refractometer and my hydrometer and I have found the two to be very close — within 1-2 points.  Ultimately, however, I run with the reading from the hydrometer.  I use my beer thief only from the carboy during fermentation.
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Offline KCguy

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Re: other methods of taking gravity readings
« Reply #17 on: April 12, 2019, 12:34:37 PM »
Also I love my new Tilt, which monitors SG the whole way, though it is a bit finicky.

OK, what is this 'Tilt' you speak of?  It sounds like you can monitor gravity in fermenting wort via your phone?  Where do you shop for this device? 
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Offline BrewBama

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Re: other methods of taking gravity readings
« Reply #18 on: April 12, 2019, 12:48:26 PM »
Also I love my new Tilt, which monitors SG the whole way, though it is a bit finicky.

OK, what is this 'Tilt' you speak of?  It sounds like you can monitor gravity in fermenting wort via your phone?  Where do you shop for this device?

https://tilthydrometer.com/


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Offline KCguy

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Re: other methods of taking gravity readings
« Reply #19 on: April 12, 2019, 01:03:31 PM »
Thanks, not sure why my searches didnt bring it up before, but this looks amazing. 
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Michael B
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Offline goose

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Re: other methods of taking gravity readings
« Reply #20 on: April 12, 2019, 01:59:20 PM »
Even though you need a lot of wort to check gravity using a hydrometer and a sample tube, the wort can be dumped back into the boil kettle with no ill effects. 

Wait - you're taking readings of hot wort?  Ive never heard of doing that - is it somehow telling you the efficiency of the wort?  Doesnt the temperature change the reading? 

I have a thief too, but the amount of wort still is too much for me.  I drink it also, it doesnt go to waste, just wish there was a better way....

Yes, I take reading of the boiling wort throughout the entire 60-90-whatever period.  When doing so, I use both my refractometer and my hydrometer and I have found the two to be very close — within 1-2 points.  Ultimately, however, I run with the reading from the hydrometer.  I use my beer thief only from the carboy during fermentation.

I do this as well to make sure that I hit my OG numbers at the end of the boil. I use the refractometer to monitor the wort throughout the boil (since I can get a quick reading and adjust boil times if necessary) and a hydrometer that measures in degrees Plato to get an accurate reading of the OG after the wort is cooled. I am usually within 1-2% of my target which is good enough for me and within the error of the measurement device, my eyes, and brewing software.  My hand held refractometer when calibrated also reads the same as my hydrometer although there are some that don't.  But that can also be compensated for by comparing hydrometer and refractometer values and adjusting the refractometer reading.

During fermentation I take several readings with the hydrometer so I don't have to play the correction game and can monitor when things are done.  If you worry about how much beer you are wasting in taking samples, just make your batches slightly larger to compensate for it.
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Offline dmtaylor

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Re: other methods of taking gravity readings
« Reply #21 on: April 12, 2019, 02:00:45 PM »
*EDIT  Yep, ran some records through.  "Old cubic" gives me virtually the same FG results as Petr's as published in Zymurgy (also used by Brewer's Friend) gives, which I've confirmed by saccharometer.

Yupper.... me too.  Almost identical within fractions of an SG point.
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Offline a10t2

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Re: other methods of taking gravity readings
« Reply #22 on: April 12, 2019, 03:07:36 PM »
*EDIT  Yep, ran some records through.  "Old cubic" gives me virtually the same FG results as Petr's as published in Zymurgy (also used by Brewer's Friend) gives, which I've confirmed by saccharometer.
Yupper.... me too.  Almost identical within fractions of an SG point.

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Offline narcout

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Re: other methods of taking gravity readings
« Reply #23 on: April 12, 2019, 05:30:51 PM »
Another thing is that for good accuracy, it needs to be calibrated, and re-calibrated, and re-re-calibrated, prior to every use, IF you want it to be very accurate within 0.001-0.002. 

Maybe I've just gotten lucky, but I've never had to calibrate or re-calibrate my Tilt. 

It consistently reads .002 lower than my hydrometer.  Maybe I could correct that with calibration, but I don't really see the need.
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Offline dmtaylor

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Re: other methods of taking gravity readings
« Reply #24 on: April 12, 2019, 06:54:10 PM »
Another thing is that for good accuracy, it needs to be calibrated, and re-calibrated, and re-re-calibrated, prior to every use, IF you want it to be very accurate within 0.001-0.002. 

Maybe I've just gotten lucky, but I've never had to calibrate or re-calibrate my Tilt. 

It consistently reads .002 lower than my hydrometer.  Maybe I could correct that with calibration, but I don't really see the need.

That sounds calibrated to me.  I've only used mine twice so far.  Maybe after nailing the cal points after another batch or two I won't need to cal anymore either.  Of course, by then I'll need to replace the battery, and then all bets are off because the weight could be different by a fraction of a gram and throw it all off again....  :D
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Offline Michael

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Re: other methods of taking gravity readings
« Reply #25 on: May 15, 2019, 12:49:02 AM »
I have a Tilt also and have used it for a couple of years. The first one died and was replaced for free even though it was out of warranty.  :) I'm now using it with a Tiltbridge http://www.tiltbridge.com/, which is awesome and makes it a lot easier to use. For spot checks before, during and after fermentation, I use the Anton Paar EasyDens.

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Offline beernutz

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Re: other methods of taking gravity readings
« Reply #26 on: May 24, 2019, 06:48:29 PM »
I found that connecting my Tilt to a Raspberry Pi Zero W running tiltpi solved my connectivity issues. 

Last August when i got it, I first tried using the tilt with an old Android phone running the Tilt app but was't happy so I spent about $30 for a RPi ZeroW kit on Amazon which has been rock solid for almost a year in 10 batches.
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Offline gav

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Re: other methods of taking gravity readings
« Reply #27 on: June 02, 2019, 08:39:42 AM »
When it comes to S.G readings there is no question that hydrometers are better than refractometers, as that is what they are designed to do. Having said that, I calibrate my digital refractometer to get the correction factor for every batch of new wort - yes the color makes a difference to the refraction index, not just the sugar content - and that is why a lot of people disparage refractometers as being inaccurate.

On the hot side, I use the corrected refractometer reading throughout the mash and boil to get my S.G., and take two hydrometer readings before and after the boil for verification. My converted refractometer readings are generally within 1 point. You do though have to be careful that there is no suspended matter in your refractometer sample. I sometimes use a tiny funnel with white filter paper. I still beats the effort to cool the wort for each hydrometer reading.

On the cold side, refractometers are the way to go, specially if you do small batches (5 gal) like me. I take a small sample from my conical every day (or twice a day) during fermentation, and at this point, all I'm looking for is trend, not accuracy. Once the Brix value stops dropping, you know you're done with attenuation. It also gives you a very good idea of hop creep during dry hopping, with very fine resolution without having to squint at a graduated glass rod in solution.

The only time I really value my lab-grade narrow-range hydrometers with temperature correction is when I'm checking finished beers for ABV, using it in tandem with my Refractometer. You have to make sure there is no CO2 in the sample.

The refractometer conversion calcs out there are numerous, and also built into BeerSmith, the software I use. The slight inaccuracy of digital refractometers vs. high-end hydrometers when trying to determine S.G. (even after fermentation, as long as you have a good I.G reading) is minuscule when it comes to the home brewing IMHO. We are after all going for repeatability, not absolutes. In a commercial environment, I can see how hydrometers make sense - the volume loss is inconsequential, and they are simple to use. Plus accurate ABV is critical for those guys.

Tilt - I'm on my second one (they swapped the first one out). I wanted to love it - great concept, and the software works great, including the tilt pi web reporting - but it has its problems. Besides krausen, dry hopping and any fermentation additions play havoc with it. (Maybe they need to think of enclosing it in a top-shielded flotation chamber attached to a conical temp-probe port, and it can run a temp controller instead of the TC probe). BTW, the temp reporting is spot-on. The Tilt is great for trend monitoring while one is away from the fermenter - I was recently on the other side of the world watching my gravity drop in my garage conical in real time. Unfortunately the bluetooth range through a steel conical is minimal. Your device - phone or raspberry pi - has to be pretty much up against the vessel wall.
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Offline Bilsch

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Re: other methods of taking gravity readings
« Reply #28 on: June 12, 2019, 12:47:22 AM »
I do fast ferment tests on all my batches therefore I don't worry about refractometer corrections since I know exactly what the terminal number is going to be. When it's done I'll do one check with a narrow scale hydrometer and thats it.