Don't use a Refractometer for FG readings. Your beers didn't stall at 1.024.

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Kalvaroo

Kalvaroo

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Quick Summary: I forgot that alcohol affects refractometer readings during fermentation, so always do checks with a hydrometer. Pictures below.

Here's my "I'm a *******" moment:

A few weeks ago I brewed my pale ale recipe and a DIPA after acquiring a few new pieces of kit.

So, I'm a fairly experienced brewer and decided to start using a refractometer for pre-boil, run-off, and starting gravities. Along with adding an O2 stone for aerating my cool wort. I hit all my marks with the gravities, and had the shortest lag times to date. So I'm excited about these beers being slightly better than previous batches. I'll probably be the only one to tell the difference either way, but it's the thought that counts.

I didn't put much though into it and continued using the refractometer to see how my beers were doing during fermentation and when to rack to secondary. Readings seemed a little off, but like I said, i didn't put any thought into it and continued pressing on.

After leaving them completely alone for a week, I decided to check them with a couple drops on my refractometer as i was planning on kegging today to continue with conditioning.

It showed 1.024, and I couldn't think this was possible, so I checked the DIPA and it said around the same thing. I started thinking my mash temperatures were off on my system and getting pissed. I thought about it for a second and realized that you can't get accurate refractometer readings if there's alcohol present. So i dug up the 'ol hydrometer that I briefly thought I had retired to double check... I got right around 1.012... spot on for my pale ale.

So I thought I'd share that... and show the comparison pictures I took.

beer1.jpg


beer2.jpg
 
You can't use a refractometer to determine AG (even with correction tables) but you can use it to tell you when things have stopped changing at which point you know the fermentation is complete.
 
I've never found any program to be all that accurate, so I just always use a hydrometer for the FG for both wine and beer.

I use my refractometer all the time for checking the brix of fruit, preboil gravity, post boil, the SG of the runnings, etc, but always a hydrometer for FG in the end.
 
Yooper said:
I've never found any program to be all that accurate, so I just always use a hydrometer for the FG for both wine and beer.

I use my refractometer all the time for checking the brix of fruit, preboil gravity, post boil, the SG of the runnings, etc, but always a hydrometer for FG in the end.
Click to expand...

I've found the same. Nothing converts it well enough, just sacrifice the few ounces of beer and use a hydrometer for any reading after there's alcohol in the mix.
 
OP, you forgot one thing. The SG scale is also off on that refractometer. I have the same one. It shows 31 Brix = 1.120 in the sight. That's way low. 31 Brix comes up as 1.128 on Sean Terrill's calculator, and even higher on some others. So, never use the SG scale on it, use his calculator, and you'll be fine.

I've tested two batches using his calculator and my hydrometer. They agreed within 1 point both times. Good enough for me - I can't see much closer than 1 point even with 20/15 vision now. I'll not waste that 3 oz of good beer each time. :) My hydrometer is now retired.

Indeed, I've found other calculators to be worse. The farthest one off was the MoreBeer spreadsheet, IIRC.
 
I'm the same, use the refrac for all non-fermenting operations. On the flip side, I've been brewing for over 25 years and have never dumped a hydrometer sample, everything is sanitized and it goes right back into the fermenter.
 
I'm a spreadsheet nerd, so here is the formula I use:

SG=1.001843-0.002318474*(OB)-0.000007775*(OB^2)-0.000000034*(OB^3)+0.00574*(FB) +0.00003344*(FB^2)+0.000000086*(FB^3)

SG = Specific Gravity
OB = Original Brix
FB = Final Brix

In this example, assuming your original Brix was 10.5 or about 1.043 and your final Brix is 6, the adjusted final specific gravity would be 1.012264886.

This pretty much matches your readings (again assuming I have correctly guessed your original gravity)
 
I just finished doing a sample testing on some finished beers using a refractometer and two different hydrometers. These are my results:

Code: 
                                Distilled       ESB    RedAle    BelgPA   CalComB   SWinSai
Temperature of sample                60.0      59.7      59.9      60.3      60.1      59.7
OG (Brix, actual)                       0      14.6     13.75      14.2        13      18.4
OG (SG, Beersmith converted)            0     1.058     1.054     1.056     1.051     1.074
OG (SG, SeanTerrill converted)          0     1.057    1.0535    1.0554    1.0505    1.0728
FG (Brix, actual)                       0       8.0       6.6       7.0      6.95       8.4
FG (Beersmith, converted)               0     1.015     1.009     1.010     1.013     1.008
FG (SeanTerrill, converted)             0    1.0152    1.0116    1.0124    1.0134    1.0119
FG (hydrometer90, actual)          1.0000    1.0145    1.0105    1.0100    1.0125    1.0090
FG (hydrometer70, actual)          1.0000    1.0170    1.0115    1.0120    1.0120    1.0095

Distilled = Distilled Water
ESB = Extra Special Bitter
RedAle = American Amber Ale
BelgPA = Belgian Pale Ale
CalComB = California Common Beer
SWinSai = Saison

I've had good correspondence in the past on random checks but had never done a complete testing of several beers for the purpose of checking accuracy of my refractometer. After conducting this testing I'm very happy to stick with simply using my refractometer and only breaking out a hydrometer if something seems really fishy. At the homebrew level, this is totally satisfactory for me and the ABV is probably within ±0.2% using a refract vs hydro. Additionally, I found that reading the hydro sample values to be more questionable on my part than reading the refract sample values.

All beer samples were pulled from kegerator tap into small glasses except CalComB; put into a warm water bath to help release co2; stirred to release co2 until there was no significant release of co2 left. Samples were brought up to about 85°F and then recooled to about 60°F using thermoworks thermometer. CCB was pulled from carboy at ~62°F, stirred, and cooled to ~60°F.

The hydrometer fourth decimal place is because I couldn't confidently say the digit up or down (e.g. 1.014-1.015 becomes 1.0145).

The hydrometers are both calibrated at 60°F so I tried to bring all samples to that temperature for this testing. Hydrometer90 is one that I purchased in the 90s when I began brewing, and hydrometer70 is one that my father purchased in the 70s when he was making fruit wine. Both are pretty standard-grade, run-of-the-mill hydros.

The refractometer is ATC and 60°F is really close to the calibration temperature of the refract (68°F). This was a Christmas present about 8 years ago and came from either Midwest or Northern Brewer, and cost in the $50-60 range.

All original starting gravities were only recorded on brewday in brix, but I've provided the converted OG values from both beersmith and seanterrill. I hope to begin capturing both refract and hydro readings on brewdays from now on.

I took pictures of each step along the way and hope to put together some kind of a collage that provides a visual example of this testing.
 
AmandaK said:
What is a hydrometer 90s? Or hydrometer 70s?
Click to expand...

:D

I was editing my post when you posted. I was adding some notes on my process.

"Hydrometer90 is one that I purchased in the 90s when I began brewing, and hydrometer70 is one that my father purchased in the 70s when he was making fruit wine."
 
Wonderful work.

I searched all of your forum posts earlier to see if you had posted the OG of these brews. I wanted to informally check what the Sean Terrill's would come out to and compare it to your picture. Unfortunately, they weren't available.

I'd be interested to see how a modern hydrometer stacks up. Too much work to re-do the experiment though. Have you applied a calibration factor to either of them?

Last thing. Don't worry about temperature so much with that ATC refractometer. The manual says to wait 30 seconds when measuring hot and cold liquids, but honestly, it reads exactly the same about 10 seconds after I hit it with hot tun runnings as it 5 minutes later.
 
One last thing about "stalled" fermentation for anybody curious:

Code: 
FG (Brix)                         0        8.0        6.6        7.0

These would have read as 1.031, 1.024, 1.027 if sighted through the refractometer using the SG scale and without applying the correction. Both no-no's.
 
thadius856 said:
Wonderful work.

I searched all of your forum posts earlier to see if you had posted the OG of these brews. I wanted to informally check what the Sean Terrill's would come out to and compare it to your picture. Unfortunately, they weren't available.

I'd be interested to see how a modern hydrometer stacks up. Too much work to re-do the experiment though. Have you applied a calibration factor to either of them?

Last thing. Don't worry about temperature so much with that ATC refractometer. The manual says to wait 30 seconds when measuring hot and cold liquids, but honestly, it reads exactly the same about 10 seconds after I hit it with hot tun runnings as it 5 minutes later.
Click to expand...

The OG of those brews were only recorded as brix on brewday. I keep a notepad cheatsheet on the counter to remind me of steps and to record measurements. If I create a picture table of this testing today I'll add the scratch sheet showing my brewday recordings of brix.

The seanterrill site estimates my OG as 1.057, 1.0535, and 1.0554, respectively. I think I'll add a column to my spreadsheet with this as well. Additionally, I'll consider taking a brewday hydro sample for comparative purposes. The brewday measurement was always the easiest anyway :D

I guess I consider my almost 20 year old hydrometer fairly modern :D. I might be able to grab another from a friend; I'll check into this. I have not applied any kind of calibration factor to my hydrometers aside from testing them in 60°F distilled water (they read 1.000). I assumed that if I took beer sample readings at their calibrated temperature (60°F) then I would not need to adjust the readings at all; am I mistaken?

I've always had good confidence in my refractometer throughout the years, and have only once noticed anything squirrelly. This was recently while I was reducing some really low gravity wort to starter gravity so I could can up some jars for future use. I was taking readings close together and was putting a spoonful of hot liquid over the crystal. After about the third time I realized the brix percentage was going down (should have been going up) and realized that the super hot liquid was increasing the temperature of the crystal thus causing the off readings. After running under cool water, drying, and let sit on the counter for a few minutes, I took another sample with just a couple drops and I was back on track. This is the only instance I've noticed inaccurate readings using a hydrometer. I feel that many folks run into inaccurate readings due to user error; just like in my case. They are great tools but have a lot more "rules" to using them then hydrometers, which makes hydrometers less prone to user error. IMO.
 
I'm with Yooper about using the hydrometer for FG.

I vaguely recall ruining a beer when I thought it stalled out (think I added water or something) - was new to refractometers.
 
All very true.

I say "modern" because I was curious to see if advances in computerization and automation of the modern factory resulted in an increase (or decrease, even) in accuracy.

If they're both still 1.000 without correction, on for over 40 years, then might as well just assume that the hydrometer is a simple enough piece of equipment that it doesn't benefit from those things.
 
Put me in the refractometer camp, enthusiastically. I use it from start to finish with both brewing and wine making. I did a lot of comparison testing before I finally decided to mothball my hydrometer and I never noticed a discrepancy that was meaningful to me (usually the same, occasionally off by 1 point, never more than 2).

Separately, if my beer finishes at 1.012 but my refractometer tells me it finished at 1.010, I'll either be able to taste it and can decide whether to adjust the recipe next time, or I won't be able to taste it, in which case, I don't really care if it's 1.012 vs 1.010. Either way, neither reading is actually going to cause me to do anything with that batch.

In some respects, I look at this the same way I do the various hop utilization formulas. Sure, they give different readings, but so what. Pick one and stick with it and you can get predictable results.
 
thadius856 said:
Even if it had stalled... water? What? Why?
Click to expand...

haha I honestly can't say for sure if I did add water (to bring the FG into proper range), but I'm thinking I did - and I don't know why I can't remember, was only about 3 years ago. I guess I panicked.
 
Updated my table (here) above with sample readings from my California Common Beer. Again, I'm finding that my refractometer and hydrometer readings have very good correspondence. I'll try to keep this up as much as I can, or remember. I wonder how the readings might stray from each other as the OG or FG goes up or down (i.e. big beer or sweet beer), and how much big body might play a factor. I have a semi-big malty saison off tap right now that I'll try to get sample values from when it comes back on tap.
 
I use my refract. Easier, less wasted beer and don't risk infection by pouring sample back into conical. Readings are close enough for the girls I go with!
 
Good data stpug. Lately I've seen more and more HBT members speaking out and saying a refractometer works for FG if you use the correction formulas. The end results are certainly as close as the hydrometer only guys get. There are as many people misreading a hydrometer 1 or 2 points off by not understanding how to read one. The biggest problem I see is the dual scale refractometers. They should never been allowed to market. I'm still rather surprised that our water expert guy and one of our mods continue to downplay a refractometer for FG. I just tell people anymore to go ahead and do your hydrometer test, then put a couple drops of that on the refractometer, use the calculators, and decide for yourself. If you have one of those dual scales, I wouldn't trust either scale.
 
I'll try to report back on Monday. I have a brew coming out of primary that was pretty close to 1.077 OG.

I have two hydrometers that are newish, one used, one never used, both from NB last July during a starter kit special. I'll let you know how they compare, if I can remember to measure my "tasting sample". :)
 
BTW to the OP. You do not have a 1.012 in that picture. It is more than likely a 1.014 - 1.015. I'm going to guess that your OG was 10.5B or 1.041
 
stpug said:
I wonder how the readings might stray from each other as the OG or FG goes up or down (i.e. big beer or sweet beer).
Click to expand...

Granted, there is a difference between wine must and wort, but I track wine fermentations that often move from approx 1.105 down to 0.985. My refractometer and hydrometer don't stray meaningfully over the entire range.
 
My reason for rejecting refractometers for even wort was that when I was considering using them I compared, over several brews hydrometer and refractometer readings. I found the refractometer to agree closely with the hydrometer (precision hdrometers) except when it didn't and in those cases it could be off by more than 1°P. As I couldn't figure out what the conditions were that caused the large errors I concluded that refractometers are fine most of the time but as you don't know when it isn't 'most of the time' they were not reliable enough. Now of course if 1 °P is within the limits of accuracy that are acceptable to you then you are in good shape with a refractometer.

When it came to beer I again compared refractometer to densitometer readings and found them to be all over the place such that no correction formula based on anything other than the particular beer would serve to give an accurate reading. ASBC does have a method for measuring beer with a refractometer and it requires exactly that i.e. a calibration curve for the particular beer which curve is to be determined with densitometer and distillation for the alcohol. The idea is that for a particular beer in the breweries portfolio individual calibration curves are good enough to accurately measure batch to batch deviations but that you couldn't use the curve for the bohermian pilsner to measure the octoberfest.

Another interesting observation about refractometers is that the ATC correction factors they have built in are for sucrose and the change in NI with temperature for beer is quite different. In my experiments I would measure NI at two different temperatures, determine the slope and correct to 20 °C before plugging into the °P vs NI or ABV vs NI formulas I was experimenting with.
 
ajdelange said:
My reason for rejecting refractometers for even wort was that when I was considering using them I compared, over several brews hydrometer and refractometer readings. I found the refractometer to agree closely with the hydrometer (precision hdrometers) except when it didn't and in those cases it could be off by more than 1°P. As I couldn't figure out what the conditions were that caused the large errors I concluded that refractometers are fine most of the time but as you don't know when it isn't 'most of the time' they were not reliable enough. Now of course if 1 °P is within the limits of accuracy that are acceptable to you then you are in good shape with a refractometer.
Click to expand...

Yikes, I might reject a refractometer too if I was noticing differences that big. Were those beers 'unusual' in any way?
 
ajdelange said:
My reason for rejecting refractometers for even wort was that when I was considering using them I compared, over several brews hydrometer and refractometer readings. I found the refractometer to agree closely with the hydrometer (precision hdrometers) except when it didn't and in those cases it could be off by more than 1°P. As I couldn't figure out what the conditions were that caused the large errors I concluded that refractometers are fine most of the time but as you don't know when it isn't 'most of the time' they were not reliable enough. Now of course if 1 °P is within the limits of accuracy that are acceptable to you then you are in good shape with a refractometer.

When it came to beer I again compared refractometer to densitometer readings and found them to be all over the place such that no correction formula based on anything other than the particular beer would serve to give an accurate reading. ASBC does have a method for measuring beer with a refractometer and it requires exactly that i.e. a calibration curve for the particular beer which curve is to be determined with densitometer and distillation for the alcohol. The idea is that for a particular beer in the breweries portfolio individual calibration curves are good enough to accurately measure batch to batch deviations but that you couldn't use the curve for the bohermian pilsner to measure the octoberfest.

Another interesting observation about refractometers is that the ATC correction factors they have built in are for sucrose and the change in NI with temperature for beer is quite different. In my experiments I would measure NI at two different temperatures, determine the slope and correct to 20 °C before plugging into the °P vs NI or ABV vs NI formulas I was experimenting with.
Click to expand...

What are you using for Brix to SG correction when alcohol is present?
 
I'm relying on memory here and it was a while ago but I can safely say that I wouldn't have been doing that. I would have been looking at the relationships between NI, OG and ABV and NI, OG and AE or TE for several beers to see if were possible to take a refractometer reading and turn it into an ABV and/or AE value without having to do what the ASBC recommends i.e. do a calibration curve using much fancier equipment for each beer or class of beers. I recall deciding that it wasn't doable and so stopped pursuing it. I can't turn up my notes on a cursory search so I'm afraid I can't give you a much better answer than that for the moment. I do clearly remember the NI vs temp. issue but not much else.
 
Updated my table here with sample readings from my semi-big, malty saison (Winter Starlight Saison).

Just to note: this saison did not finish as low as I had expected it to and had an unusually bigger body than expected, therefore I thought it would be a good candidate for comparison because of the perceived residual sugar and thick mouthfeel. I notice that of all beers I've sampled that this one has the most variance in calculated SG between beersmith and seanterrill (4 points, basically). I think that 4 points is significant because in this beer it is almost 1% ABV difference. One interesting point is that the hydro readings basically split the difference of the 4 points making each only about 2 points away which I find to be much better margin of error. Anyway, just thought this was worth mentioning. Again, I'll keep trying to add to this as I remember and have the time.
 
OP here...

Thanks for all the input... I think i'm just going to stick with using a hydrometer for my final readings for right now instead of doing the conversion. I'll play around with using brix and doing the conversions on my next batch and see how it goes.

Here's my numbers so you guys can keep playing around with the math... if you want. Notice how my refractomter readings for final gravity were different, but the same when measured with a hydrometer.

What I was shooting for:

Pale Ale: 5.5% ABV / OG 1.054
DIPA: 7% - 8% ABV / OG 1.065 - 1.075


What I got for Original gravities: (Measured with Refractometer, right before pitching yeast)

Pale Ale: 1.054
DIPA: 1.065

Final gravities: (Measured with Hydrometer)

Pale Ale: 1.012*
DIPA: 1.012*

*Someone implied that i don't know how to read a hydrometer. Both were read at the bottom of the meniscus... If they were read at the top I would've put them at around 1.010 - 1.011. The top of the meniscus in the picture i posted was at around 1.0105.

Final gravities: (w/Refractometer)

Pale Ale: 6 Brix 1.024 SG
DIPA: 7.5 Brix 1.029 SG


I pretty much got what I was going for... I just freaked out for a second when I initially tried to take FG readings with a Refractomter.
 
Kalvaroo said:
Final gravities: (Measured with Hydrometer)

Pale Ale: 1.012*
DIPA: 1.012*

Final gravities: (w/Refractometer)

Pale Ale: 6 Brix 1.024 SG
DIPA: 7.5 Brix 1.029 SG
Click to expand...

The corrected final gravities for your refractometer readings would be:
Pale Ale: 1.005 SG (BS) or 1.0096 (ST)
DIPA: 1.007 SG (BS) or 1.0114 (ST)

...which still would not be right unless you were brewing with saison yeast :D.

I would agree that in your case you are better off using a hydrometer for your readings because your hydro vs refract final gravities are starkly different (with the exception of "DIPA refract ST" reading). I'm not finding this kind of variance in my sample testing with my equipment and I cannot explain why such a difference.
 
stpug said:
The corrected final gravities for your refractometer readings would be:
Pale Ale: 1.005 SG (BS) or 1.0096 (ST)
DIPA: 1.007 SG (BS) or 1.0114 (ST)

...which still would not be right unless you were brewing with saison yeast :D.

I would agree that in your case you are better off using a hydrometer for your readings because your hydro vs refract final gravities are starkly different (with the exception of "DIPA refract ST" reading). I'm not finding this kind of variance in my sample testing with my equipment and I cannot explain why such a difference.
Click to expand...

Where'd you get these numbers?

For the Pale, I get OG 13.95 Brix, FG 6 Brix. Converted FG 1.0095, 5.7% ABV/4.5% ABW.

For the DIPA, we don't really know the OG. At 1.0119 converted FG and 7.5 Brix FG measured, I come out with 16.1 Brix OG (1.0632). This one's a little too fuzzy without a measured OG to trust, though.
 
The explanation is that there is no accurate 'rule' that maps pre and post fermentation Bx readings into a FG reading for all beers. If you 'plot' SG vs the original Bx and final Bx for a whole lot of beers you will find the points more or less describe a surface and you can do a two dimensional curve fit to that surface and the majority of the points will lie close to the surface represented by the curve fit but some will be quite far off. It is in the nature of beer.
 
thadius856 said:
Where'd you get these numbers?

For the Pale, I get OG 13.95 Brix, FG 6 Brix. Converted FG 1.0095, 5.7% ABV/4.5% ABW.

For the DIPA, we don't really know the OG. At 1.0119 converted FG and 7.5 Brix FG measured, I come out with 16.1 Brix OG (1.0632). This one's a little too fuzzy without a measured OG to trust, though.
Click to expand...

I used the OPs SG numbers (1.054 and 1.065). Then using their photo in the original post, I tried to determine a brix % (13.8% and 16.6%, respectively).

Using the starting gravity/brix and finishing brix, I implemented beersmith's (BS) calculator and SeanTerrill's (ST) calculator.

The really low numbers were produced by BS calculator and the more reasonable numbers were produced by ST calculator.
 

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