Using refractometer during fermentation

[h22lude]

I either used my hydrometer wrong or my refractometer calculations are a little off. I brewed a batch Friday and did a fast ferment test to see what the FG should be. I just took the reading and I also took a reading of the actual beer to see where it was at.

OG
Hydro - 1.054 (13.32 °Bx)
Refracto - 1.056 (13.79 °Bx)

Wort Correction Factor - 1.027...I have taken a few different readings to get this as an average.

FFT FG (spot on)
Hydro - 1.009 (2.31 °Bx)
Refracto - 1.023 (5.85 °Bx)
Corrected Refracto - 1.009 (2.31 °Bx)

Beer currently (hydro and refracto don't match)
Hydro - 1.023 (5.82 °Bx)
Refracto - 1.031 (7.8 °Bx)
Correct Refracto - 1.015 (3.82 °Bx)

I stirred the beer sample for a minute to get any CO2 out of solution and then let it sit for probably 30 minutes (I forgot about it).

Since my FFT gravity correction was spot on, I assume the calculator I used is working properly. Is there a reason the beer refractometer and hydrometer readings were off? I would assume with the wort correction factor and using Sean Terrill's calculator the batch gravity readings should have matched. Now I don't know if the hydro reading or the refracto reading was off.

 

[schematix]

Story of my life with hydro/refract.

Just can’t get them to work consistently. Sometimes they are exact, sometimes with same wort I get different readings even when hydrometer is the same.

I put a digital refract on my Xmas list. Didn’t come but there’s an unopened Amazon box in the basement... fingers crossed I’ll have one for my birthday in a few weeks.

 

[h22lude]

Story of my life with hydro/refract.

Just can’t get them to work consistently. Sometimes they are exact, sometimes with same wort I get different readings even when hydrometer is the same.

I put a digital refract on my Xmas list. Didn’t come but there’s an unopened Amazon box in the basement... fingers crossed I’ll have one for my birthday in a few weeks.

So this has happened to you before too? Seems like a lot of people, after getting a good wort correction factor, stop using their hydrometer all together. With this happening to me just this one time, I will always be wondering if my refractometer is correct. I need to transfer this beer to spunding at 1.015. I would have done that today if I just used my refractometer to take a reading.

Do you think it is the manual refractometer that is causing the issue? I have been looking at a digital one as well...but would this happen with those as well?

 

[ba-brewer]

I sometime have greater differences between the hydro and refractometer with darker beers, light colored beers track better. Even though I do the calculations I mostly just use the refractor reading during fermentation as a relative measurement to find when fermentation has ended.

Also seems the Terrill calculator does not track so well when the calculation give a value below 1010.

 

[lump42]

There's a new formula from a guy in Finland that claims to be more accurate than the Terrill formula. I haven't tested it out but may be worth looking at. You have to create a free account to use their calculator.
https://www.homebrewmap.com/en/tools/calculators/refractometer-correction

 

[schematix]

So this has happened to you before too? Seems like a lot of people, after getting a good wort correction factor, stop using their hydrometer all together. With this happening to me just this one time, I will always be wondering if my refractometer is correct. I need to transfer this beer to spunding at 1.015. I would have done that today if I just used my refractometer to take a reading.

Do you think it is the manual refractometer that is causing the issue? I have been looking at a digital one as well...but would this happen with those as well?

I have a handheld “manual” refract. It does bizarre stuff sometimes. Like some days distilled water reads 0, while others are 0.2-0.4. Even days back to back to back.

Every time I’ve made a reference sucrose solution it’s been exact though.

I’ve had wort correction factors from close to 0.9 all the way to near 1.1. Even same recipe back to same has had unexplainable differences in factor.

I’ve had preboil gravity measure the same as post boil on an alarmingly consistent basis.

Its an utterly useless and unreliable tool in my experience and I’ve had one for about 6 years. I keep dreaming that one day it’s going to save me the hassle of using my precision hydrometer.

The precision hydrometer is the most trusted tool in all of my brewery, even more so than my good thermometers.

 

[h22lude]

So I used Sean's calculator and the one from HomeBrewMap. They are pretty close to each other. I actually found Sean's to be closer to my hydro reading. With my fast ferment test I got 1.009 from my hydro and using Sean's I got 1.009. I got 1.006 using HomeBrewMap.

I have a handheld “manual” refract. It does bizarre stuff sometimes. Like some days distilled water reads 0, while others are 0.2-0.4. Even days back to back to back.

Every time I’ve made a reference sucrose solution it’s been exact though.

I’ve had wort correction factors from close to 0.9 all the way to near 1.1. Even same recipe back to same has had unexplainable differences in factor.

I’ve had preboil gravity measure the same as post boil on an alarmingly consistent basis.

Its an utterly useless and unreliable tool in my experience and I’ve had one for about 6 years. I keep dreaming that one day it’s going to save me the hassle of using my precision hydrometer.

The precision hydrometer is the most trusted tool in all of my brewery, even more so than my good thermometers.

I'm guessing my refracto reading was off. I checked it with my finishing hydro and that was over 1.020 which agrees with my general hydro of 1.023. I've been relying on the refracto for a long time. Guess I shouldn't have.

Now I'm curious to see how a digital refracto works. Could that be off as well? I know it will always be off with alcohol but will it also be off like my handheld manual one was today?

 

[h22lude]

Just retested and got the same results. Both hydros are reading about 1.022ish. Refracto corrected gravity is about 1.014. No clue why this would be happening. I put the beer in a shaker to remove as much CO2 as possible. I made sure the temp was right too. Never had this problem before...or maybe I always have and never noticed it.

 

[ancientmariner52]

Are you using the same light source each time for the refractometer? I don't know for certain that this could change the reading. However, I once made a 500 mile round trip to troubleshoot an automated video measuring system. Turned out the seasons had changed, and the QA lab people had opened some blinds. Completely confused the software by changing the light source.

 

[phillipe]

Just noticed this thread. Not sure if the Finland reference is the same, but there is a nice article in the July/August Zymurgy issue about discrepancies with Sean's equation and a method for refractometer correction.

 

[h22lude]

Are you using the same light source each time for the refractometer? I don't know for certain that this could change the reading. However, I once made a 500 mile round trip to troubleshoot an automated video measuring system. Turned out the seasons had changed, and the QA lab people had opened some blinds. Completely confused the software by changing the light source.

Ha, that is pretty interesting. Yeah I was using the same light. Even tried different ones.

Just noticed this thread. Not sure if the Finland reference is the same, but there is a nice article in the July/August Zymurgy issue about discrepancies with Sean's equation and a method for refractometer correction.

I don't remember getting that one. I'll have to look online. I'll check it out.

I guess for now the best option is to go by the hydro readings.

 

[ancientmariner52]

Gotcha. Just one of them random thoughts.

 

[dmtaylor]

There's a new formula from a guy in Finland that claims to be more accurate than the Terrill formula. I haven't tested it out but may be worth looking at. You have to create a free account to use their calculator.
https://www.homebrewmap.com/en/tools/calculators/refractometer-correction

+1. I have had better success with the new Novotny formula than the Terrill formula.

Just noticed this thread. Not sure if the Finland reference is the same, but there is a nice article in the July/August Zymurgy issue about discrepancies with Sean's equation and a method for refractometer correction.

It's the same guy.

My guess is the 1.015 value was closer to accurate. Keep in mind that alcohol will evaporate, so leaving a sample sitting around for 30 minutes prior to measurement will tend to result in a higher reading than if you had recorded the reading immediately.

 

[h22lude]

So I put the second sample in the fridge for a few hours then took it out and left it on my counter overnight. I checked my two hydros this morning. Both readings now match the refracto after wort correction factor and alcohol calculation. I've never seen this before. If I had to guess, this beer has more CO2 in solution than normal. It is fermenting at 55°F which would cause a little more to get into solution than if it was in the mid 60s. The blow off tube could also have a small clog letting less CO2 out so more stays in my FV.

 

[dmtaylor]

So I put the second sample in the fridge for a few hours then took it out and left it on my counter overnight. I checked my two hydros this morning. Both readings now match the refracto after wort correction factor and alcohol calculation. I've never seen this before. If I had to guess, this beer has more CO2 in solution than normal. It is fermenting at 55°F which would cause a little more to get into solution than if it was in the mid 60s. The blow off tube could also have a small clog letting less CO2 out so more stays in my FV.

Interesting. So what is the gravity and Brix reading today?

 

[h22lude]

Interesting. So what is the gravity and Brix reading today?

I didn't take a new sample so all my readings were from the sample I took yesterday. Refracto was the same but the hydros were now down to 1.015ish.

I think going forward I'm going to put any fermenting sample through a coffee filter first. That is supposed to knock out all CO2.

 

[dmtaylor]

I've never been concerned about CO2. If you want to remove CO2 from any sample within seconds, just add like 1/8 teaspoon of baking soda and let it foam up. Done.

 

[h22lude]

I've never been concerned about CO2. If you want to remove CO2 from any sample within seconds, just add like 1/8 teaspoon of baking soda and let it foam up. Done.

I've never been considered until now. The CO2 caused both hydros to be about 10 points off. That's huge.

 

[dmtaylor]

I actually stir my samples vigorously. The baking soda thing was just a eureka thought I had, but I am not certain it's the best solution. Just stir the mother out of the sample to get the fizz out and your readings should come out fine.

 

[h22lude]

I actually stir my samples vigorously. The baking soda thing was just a eureka thought I had, but I am not certain it's the best solution. Just stir the mother out of the sample to get the fizz out and your readings should come out fine.

That is exactly what I did. I put it in a shaker and shook it up. I then stirred it with a fork. Still was off. Might have had more CO2 than normal for some reason. I'm just going to use a coffee filter going forward. Cheap, very easy and effective.

 

[dmtaylor]

Interesting. Never would have thought of a coffee filter.

 

[brezam]

Just noticed this thread. Not sure if the Finland reference is the same, but there is a nice article in the July/August Zymurgy issue about discrepancies with Sean's equation and a method for refractometer correction.

It doesn't come from Finish but from Czech guy and yes - HomeBrewMap calculator uses formula described in Zymurgy...

 

[dmtaylor]

It doesn't come from Finish but from Czech guy

Oh I think you are right... Czech.

 

[augiedoggy]

my brewing buddy and I use two different refractometers when brewing just to be sure our readings are good, also ive noticed if I take a sample and read it and wait about a minute and read it again that it sometimes goes up a bit possibly from cooling? drives me nuts.
Ive been doing a lot of changes to my brewing procedures lately for more efficiency (up to 92.7% on last brew) so weve bee taking may samples and quadruple checking them... I have a cheap refractometer and he has an expensive heavy one (only does brix) at least they read consistently with each other or within .001

 

[schematix]

Just stumbled across this thread again while googling for something different, but related and thought i'd post some updates.

Refractometers can be used successfully, but care must be taken:

1. Clear samples are required.
2. Degassed samples are required.
3. Sample temperature should be same as instrument temperature.
4. If the sample has undergone any fermentation its required to use a correction formula.
5. Keep a record of wort OG and FG samples in both Brix and Plato or SG until you are comfortable you know the correction factor for your instrument.

Until I started filtering samples through a coffee filter my digital refract was ALL over the place. Now i filter, insert the sample, wait 30 seconds, take 4 measurements, average them (usually only deviation of 0.1 B).

I'm now comfortable enough that i just use the hydrometer for an accurate OG and then a single sample after the beer has cold conditioned for a few weeks to determine real FG (since i do a lot of lagers and spund sometimes i don't know exactly where it's going to land).