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General Category => All Grain Brewing => Topic started by: KCguy on April 11, 2019, 12:06:37 PM

Title: other methods of taking gravity readings
Post by: KCguy on April 11, 2019, 12:06:37 PM
I usually use the old fashioned hydrometer, but its always bothered me how much wort it sacrifices.  And even though Ive sanitized it beforehand, I never trusted pouring that back in the fermenter.  O2, infection...too many risks there...

Also tried a refractometer, but misunderstood and later learned it was only intended for use before adding yeast; I wanted to take readings throughout fermentation.

I guess my question is does anyone take frequent readings to monitor fermentation and if so, how if different than the above types. 
Title: Re: other methods of taking gravity readings
Post by: KellerBrauer on April 11, 2019, 12:24:30 PM
Using a hydrometer is the most accurate way of checking gravity, unless you spend loads of money on an electronic device.

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.  However, after fermentation begins, I use a beer thief to grab a sample, drop in my hydrometer and take a reading.  When I’m done, I dump the sample onto a small tasting glass and drink it. The sample is about 3-4 oz.

https://www.amazon.com/Fermtech-Wine-Beer-Thief-Long/dp/B00BTMWXC6/ref=sr_1_3?crid=979XE15U7GHS&keywords=beer+thief&qid=1554985069&s=gateway&sprefix=Beer+theif%2Caps%2C1279&sr=8-3

Check it out.
Title: Re: other methods of taking gravity readings
Post by: KCguy on April 11, 2019, 12:45:43 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....
Title: Re: other methods of taking gravity readings
Post by: Big Monk on April 11, 2019, 01:17:51 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. 

...is it somehow telling you the efficiency of the wort? 

I mean, technically speaking, knowing your gravity DOES tell you your efficiency.

Doesn't the temperature change the reading? 

Yes. You have to correct using the following:

S.G. Correction Factor = 1.00130346-(1.34722124*POWER(10,-4)*°F)+(2.04052596*POWER(10,-6)*POWER(°F,2))-(2.32820948*POWER(10,-9)*POWER(°F,3))

So if you measure your wort at 158 °F and get a reading of 1.045, the actual S.G. reading is going to be 1.067.

You can also use a refractometer, although you have to know the correction factor for your unit beforehand. You can get a good estimate by measuring known solutions of water and sugar and then substituting the correct correction factor for the wort gravity you are aiming for.
Title: Re: other methods of taking gravity readings
Post by: Robert on April 11, 2019, 01:55:07 PM
I use a refractometer now throughout the brewing and fermentation process.   I do still have a good set of narrow range, professional, brewery saccharometers (Plato hydrometer with built in thermometer and correction scale.)  I long fancied the idea of using a refractometer for the ease of use and small sample size,  but I had given up on my old hand held, optical refractometer. It was quite untrustworthy.  But I have a digital refractometer now,  and it turns out there is no such thing as a "correction factor for the unit."  I'm now convinced that the origin of the idea of such a correction among users of hand held optical units is in fact correction for the vagaries of the users' eyeballs. The digital one works perfectly, measurements confirmed by saccharometer.  You can in fact take readings through fermentation,  but you do need to correct for the presence of alcohol or the reading will be not just inaccurate but completely meaningless.  Read the article on refractometer use by Petr Novotný in the July/August 2017 Zymurgy.  The free calculator at Brewer's Friend uses his equation, if I'm not mistaken.  I've incorporated it into my own spreadsheet and found it to be quite reliable.
Title: Re: other methods of taking gravity readings
Post by: case thrower on April 11, 2019, 03:13:00 PM
Rob, do you have a link for the digital refractometer you use?  And are there any concerns about using it at higher temperatures?
Title: Re: other methods of taking gravity readings
Post by: Robert on April 11, 2019, 04:56:48 PM
Rob, do you have a link for the digital refractometer you use?  And are there any concerns about using it at higher temperatures?
It only takes a couple of drops of wort on the prism, so that cools mighty fast.  And the unit has automatic temperature correction  built in, in case it's still a different temperature than when calibrated with distilled or RO water.  I believe MoreBeer sell this too, maybe labeled as a wine refractometer.   The instruments are identical AFAIK, just one calls the readout Brix and the other Plato.  So you could compare prices between MoreBeer and the manufacturer.

https://hannainst.com/hi96841-digital-refractometer-for-beer.html
Title: Re: other methods of taking gravity readings
Post by: dmtaylor on April 11, 2019, 06:19:22 PM
Refractometer works just fine as long as you learn your correction factor (mine is 0.99) and use the Brewer's Friend calculator or equivalent.  The website does explain how to figure out the correction factor.

https://www.brewersfriend.com/refractometer-calculator/

Also I love my new Tilt, which monitors SG the whole way, though it is a bit finicky.
Title: Re: other methods of taking gravity readings
Post by: spurviance on April 11, 2019, 08:33:44 PM
Also I love my new Tilt, which monitors SG the whole way, though it is a bit finicky.

What is finicky about the Tilt?  I am an extreme tightwad but if I was going to splurge on a brewing accessory this might be the one as it seems to solve all the above mentioned issues with refractometers and hydrometers.
Title: Re: other methods of taking gravity readings
Post by: BrewnWKopperKat on April 11, 2019, 08:57:48 PM
After working with new technology on weekdays, I like the idea of an 'old fashioned hydrometer' when I'm brewing on the weekends.  No correction factors to calculate, no WiFi or Bluetooth connections to troubleshoot (and no batteries to charge  ;) ).

So when I'm brewing "house" recipes, I'm brewing to a desired result (12-pack, 24-pack, ...).  I'm working towards scaling up recipes slightly to include some extra wort for the a couple of hydrometer measurements.

With new or experimental recipes, I'm less concerned about hitting the desired result - if I have to take an extra hydrometer measurement (and come up a bottle sort), that's OK.

 
Title: Re: other methods of taking gravity readings
Post by: dmtaylor on April 11, 2019, 09:25:04 PM
Also I love my new Tilt, which monitors SG the whole way, though it is a bit finicky.

What is finicky about the Tilt?  I am an extreme tightwad but if I was going to splurge on a brewing accessory this might be the one as it seems to solve all the above mentioned issues with refractometers and hydrometers.

The Tilt requires Bluetooth technology and/or faulty phone app... which for some reason tends to get disconnected every 2-6 hours, at least that's been my experience but I know for certain I'm not the only one, I've heard reports of same or similar from several others.  This means we need to manually unclick and re-click the Bluetooth connection every so often to re-establish connection.  Not a real big deal unless you're going to be away for a whole day and REALLY NEED to know the exact SG at all times..... personally I don't sweat it too much, I just enjoy seeing the trend and knowing when to change temperature or dry hop or whatever.  On the other hand, you're about equally likely to be one of the lucky people who never have this problem.  Flip a coin.  Maybe you'll be lucky.  I'm never so lucky.

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.  If that level of accuracy isn't important, great, skip the extra calibration steps and you'll still be happy.  But if you're retentive like I am, the extra calibration necessary is a little bit of a pain.  Personally I'm pretty content (so far, anyway) to deal with it because to me it's worth the little extra effort.

The other touchy thing with Tilt is that after it has krausen and/or hops stuck to it, it tends to read low by approximately 0.002 or thereabouts (in my experience).  But as long as you know this, you can easily correct for it at the end of fermentation.  You can gently shake the fermenter to get some of it off, or just live with a reading that's a little off.

Alternatively........ I really really REALLY love my refractometer, now that I know how to use it correctly.  See link from my previous post above.  It's friggin awesome, and accurate within 0.001-0.002 every time without a lot of extra calibration steps.  A couple drops and you're good to go -- how easy is that!  And cheap!
Title: other methods of taking gravity readings
Post by: tommymorris on April 11, 2019, 09:53:12 PM
Also I love my new Tilt, which monitors SG the whole way, though it is a bit finicky.

What is finicky about the Tilt?  I am an extreme tightwad but if I was going to splurge on a brewing accessory this might be the one as it seems to solve all the above mentioned issues with refractometers and hydrometers.
Readings are sometimes affected by the krausen sticking to it. Supposedly that resolved itself once the krausen drops.

I have one but have not used enough to comment.

Correction: you calibrate the Tilt in water. Not with a hydrometer. I am getting old and remembered wrong. Scary.
Title: Re: other methods of taking gravity readings
Post by: a10t2 on April 12, 2019, 12:15:58 AM
Read the article on refractometer use by Petr Novotný in the July/August 2017 Zymurgy.  The free calculator at Brewer's Friend uses his equation, if I'm not mistaken.

Just be aware that Petr's correlation is targeted at being accurate for fermenting wort, not for precision FG readings.
Title: Re: other methods of taking gravity readings
Post by: Robert on April 12, 2019, 12:32:21 AM
Read the article on refractometer use by Petr Novotný in the July/August 2017 Zymurgy.  The free calculator at Brewer's Friend uses his equation, if I'm not mistaken.

Just be aware that Petr's correlation is targeted at being accurate for fermenting wort, not for precision FG readings.
I do get accurate FG values with his formula though.  Confirmed with measurements by a hydrometer/ saccharometer/ floaty thing, they're within the margin of my ability to read said floaty thing accurately. In fact one of the advantages I see in a refractometer is that it's not lifted up by bubbles, and I don't have to worry about seeing it through hazy beer or foam. 

When I was going through a long period of acclimation and convincing myself a refractometer would really work, I found the two most reliable formulas, about equal, to be his and one of yours.  I can't remember which of yours, except that I don't think it was your "new cubic."  Anywho, it's consistent and more than good enough, since I don't need to satisfy the revenuers as to the alcohol content of my beer anyway.
Title: Re: other methods of taking gravity readings
Post by: dmtaylor on April 12, 2019, 01:10:25 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)
Title: Re: other methods of taking gravity readings
Post by: Robert 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.
Title: Re: other methods of taking gravity readings
Post by: KellerBrauer 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.
Title: Re: other methods of taking gravity readings
Post by: KCguy 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? 
Title: Re: other methods of taking gravity readings
Post by: BrewBama 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/


Sent from my iPad using Tapatalk
Title: Re: other methods of taking gravity readings
Post by: KCguy on April 12, 2019, 01:03:31 PM
Thanks, not sure why my searches didnt bring it up before, but this looks amazing. 
Title: Re: other methods of taking gravity readings
Post by: goose 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.
Title: Re: other methods of taking gravity readings
Post by: dmtaylor 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.
Title: Re: other methods of taking gravity readings
Post by: a10t2 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.

And 9 years later, we've come full circle. ::)
Title: Re: other methods of taking gravity readings
Post by: narcout 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.
Title: Re: other methods of taking gravity readings
Post by: dmtaylor 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
Title: Re: other methods of taking gravity readings
Post by: Michael 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/ (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.

Michael
Title: Re: other methods of taking gravity readings
Post by: beernutz 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.
Title: Re: other methods of taking gravity readings
Post by: gav 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.
Title: Re: other methods of taking gravity readings
Post by: Bilsch 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.