Refractometer calibration...

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GHBWNY

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I used my refractometer for the first time today. Instructions said to calibrate it with "distilled" water. I didn't have any handy and already had a wort sample pulled, so I calibrated it with tap water (which is filtered, not distilled) and tested it. Brix is 5.3 - 5.4, whereas current hydro SG reading converts to an ABV of 5.12%. Does this amount of difference between the two readings mean I should recalibrate refracto with distilled water and re-test? If not, which reading should I believe?
 
You should calibrate it properly no matter what, otherwise why did you buy the damn thing!


Almost Famous Brewing Company
 
Hey Pete,
The Brix reading is easier to compare to the SG, not the potential ABV.
Multiply the Brix by 4 to get close to the SG.

I.E., by your numbers the hydrometer reading should be ~1.021

Refractometers are horrible for reading the final gravity. Just saying . . .

'da Kid
 
I used my refractometer for the first time today. Instructions said to calibrate it with "distilled" water. I didn't have any handy and already had a wort sample pulled, so I calibrated it with tap water (which is filtered, not distilled) and tested it. Brix is 5.3 - 5.4, whereas current hydro SG reading converts to an ABV of 5.12%. Does this amount of difference between the two readings mean I should recalibrate refracto with distilled water and re-test?

I have been using a refractometer for some time now.......... and found that it and the hydrometer are never in complete agreement....... which is to be expected. They are measuring different things. One is measuring the actual density of the liquid (hydrometer), and the other the dissolved solids as it effects light refraction. It's unrealistic to expect complete agreement.

I would suggest making up a number of sugar solutions of different percentages... measure each with each device, and if you find a significant and consistent difference make a note of that difference, and try to adjust it out.

The fact is that we are brewing with tap water as a rule.......... You are measuring against tap water as your baseline...... who cares about absolute readings? We are looking at how much dissolved sugars we have in tap water......not in distilled water, and we are looking at attenuation of those sugars and increasing alcohol percentage (lighter than water).

I've never calibrated with distilled water...... would never consider doing it. In theory at least, if you calibrate according to distilled water, but you brew using tap water, and you are shooting for an OG, that OG will not accurately represent the sugar content if your baseline is distilled water.

For the most USEFUL results......... calibrate with the water you are using to brew with,and let the chips fall where they may!


H.W.
 
You should calibrate it properly no matter what, otherwise why did you buy the damn thing!

Good thought... in theory. Having read Owly's post above, it seems I may have unknowingly calibrated it properly. It would seem to be common sense to calibrate the instrument with the exact same water I am brewing with. While I still wonder why the maker would insist upon distilled (de-mineralized), I guess in the final analysis, while the comparisons are interesting between the instuments, my hydrometer is the one I'm going to use and depend upon most. Thanks, everyone.
 
Perhaps I did not understand what you said, but it looks like you have a major problem.
If you got a reading of 5.3 - 5.4 Brix, this translates to a SG of 1.021 - 1.022, which in turn should give an ABV of ~3.5% (according to my triple scale hydrometer).
If your hydrometer shows an ABV content of 5.12%, then (according to my triple scale hydrometer), this translates to about 9.5 Brix

The reason for the manufacturer specifying distilled water is that the manufacture has no idea what you're using the refractometer for, and distilled water is commonly available at low cost, and should produce a reading of 0 Brix.

With my tap water (which is fairly soft) I can use distilled or tap water, and they both read 0 Brix.

-a.
 
Perhaps I did not understand what you said, but it looks like you have a major problem.
If you got a reading of 5.3 - 5.4 Brix, this translates to a SG of 1.021 - 1.022, which in turn should give an ABV of ~3.5% (according to my triple scale hydrometer).
If your hydrometer shows an ABV content of 5.12%, then (according to my triple scale hydrometer), this translates to about 9.5 Brix

The reason for the manufacturer specifying distilled water is that the manufacture has no idea what you're using the refractometer for, and distilled water is commonly available at low cost, and should produce a reading of 0 Brix.

With my tap water (which is fairly soft) I can use distilled or tap water, and they both read 0 Brix.

-a.

This, distilled water is like a dollar for a gallon to last you forever...grab one before your next brew.
 
This, distilled water is like a dollar for a gallon to last you forever...grab one before your next brew.

From what I've read everyone that has checked their refractometer using both distilled and tap water has said that the difference between the 2 is virtually nil so why waste your money on distilled water if the only thing your going to use it for is to calibrate your refractometer once in a while?

If you really feel like using distilled water then bring some of your tap water to a boil, put a lid on the pot, wait until said lid collects some droplets on it, and grab those droplets with your eyedropper.
 
Good thought... in theory. Having read Owly's post above, it seems I may have unknowingly calibrated it properly. It would seem to be common sense to calibrate the instrument with the exact same water I am brewing with. While I still wonder why the maker would insist upon distilled (de-mineralized), I guess in the final analysis, while the comparisons are interesting between the instuments, my hydrometer is the one I'm going to use and depend upon most. Thanks, everyone.

Pete,
Use your refractometer as a quick check on how things are proceeding during the boil. Say your gravity is not as high as planned and you just passed the 15-min mark. Now is the time to add 4 or 8 or more ounces of DME to get you to that number. (I'm a 5gal boiler . . . +/- a quart or two.)

I cannot recommend measuring hot wort with your hydrometer. I lost one that way.

Your refractometer can also help after the boil to determine if you need to add any water. You can quickly measure the SG and know how much more water to add without going under your planned gravity.



I only use the hydrometer three times now.
1) Just before the yeast is pitched
2) Sample 10-14 days later for an SG reading to compare in the next few days
3) A final reading to make sure gravity has not changed from the prior sample.

'da Kid
 
Perhaps I did not understand what you said, but it looks like you have a major problem.
If you got a reading of 5.3 - 5.4 Brix, this translates to a SG of 1.021 - 1.022, which in turn should give an ABV of ~3.5% (according to my triple scale hydrometer).
If your hydrometer shows an ABV content of 5.12%, then (according to my triple scale hydrometer), this translates to about 9.5 Brix


My OG was 1.049, FG was 1.016. By the "OG - FG X 131" formulation, ABV is 4.3.

I came up with the 5.12 ABV by using the "Brewer's Friend Online ABV Calculator". I just punched the numbers in again and got the same number for their "standard" equation. However, I typed the numbers into their "alternate" equation and it came out to 4.4 ABV. Close to my 4.3 hydro reading. Just coincidence? Or was I using the wrong equation on their site?
 
OK looks like we're both misunderstanding
smile.gif

For my part, I misunderstood your comment about the hydrometer reading converting to 5.12. This gives a totally different value then the ABV scale on a hydrometer, so ignore my comments on converting the ABV reading to Brix.
When using the Brewers Friend calculator, you need to click on the "update" button when you have the original and final gravities entered. This will give you an estimated ABV of 4.33% not 5.12% using the standard calculation.
Now, if I understand you correctly, you have only used the refractometer on a sample of wort that had been fermented and turned into beer, and tried to make sense of the refractometer vs hydrometer readings at this point. Unfortunately this will not be accurate as the fermentation process converts sugars into alcohol, and the presence of alcohol interferes with the conversion from Brix to SG.
Here are my recommendations for using and checking the accuracy of a refractometer, combined with an explanation of how a refractometer works. I use Brewers Friend calculators to assist as I have checked them for accuracy.

  • A hydrometer measures the relative density of a solution (i.e. the density of that solution relative to that of water), while a refractometer measures the refractive index of a solution (i.e. the degree by which that solution bends light).
  • Before fermentation, adding sugars to the solution increases both the relative density and the refractive index of that solution, allowing the refractometer reading to be translated (approximately) to a specific gravity reading.
  • A Refractometer usually reads in Brix, which identifies the % Sucrose dissolved in water, while a hydrometer usually reads in Balling, Plato, or Specific Gravity. Balling, Brix, and Plato are for all intents and purposes identical, but Brix (as measured by a refractometer) is based on an interpretation of the refractive index assuming that the solution being measured is a Sucrose solution, while the others are expressions of the density of the solution. Because of this difference, the refractometer reading has to be corrected by applying a wort correction factor. The correction is made by dividing the reported Brix by the wort correction factor.
  • Once the correction has been made, the reading can be converted to specific gravity using the formula [FONT=&quot]SG = 1+ (Brix / (258.6 – ((Brix/258.2) *227.1))). There are other equations of greater or less complexity, but the quoted equation is used by Brewers Friend, and is accurate to 1 gravity point within the range of measurements used in brewing.[/FONT]
  • [FONT=&quot]To determine the appropriate wort correction factor see http://www.brewersfriend.com/how-to-determine-your-refractometers-wort-correction-factor/ You need to use a hydrometer and the refractometer to measure the SG and reported Brix, and enter them into the spreadsheet. Brewers Friend suggests that you take a refractometer reading 5 times for each sample of wort, and enter the average reading into the Brix field. If I do this, I get 5 identical refractometer readings, so I only take one reading.[/FONT]
  • [FONT=&quot]After performing a few batches (they recommend 6 batches), you get an average wort correction factor that you can enter into Brewer's Friends refractometer calculator without having to take any more hydrometer readings. The purpose of performing the calculations multiple times, is to eliminate measurement errors.[/FONT]
  • [FONT=&quot]A deviation of 0.01 in the wort correction factor causes a difference less than 1 gravity point for a 1.050 beer. When making a new recipe, I always recalculate the wort correction factor, and if it is different from the average by more that 0.01, I start a new spreadsheet for that recipe. This is because different grain bill combinations can require a different wort correction factor. The only instance I have found where this presents a problem is when using torrified wheat in a recipe, which reduces the wort correction factor by about 0.03.[/FONT]
All the above deals with using a refractometer and software to estimate the specific gravity prior to fermentation. Once fermentation starts however, things get a lot more complicated. The yeast consumes the sugars in the beer (which lowers the specific gravity), and produces alcohol as a by product. Is alcohol is less dense than water, the production of alcohol lowers the specific gravity even more. However, when using a refractometer, it does not measure specific gravity; it measures the refractive index. Reducing the amount of sugars (which lowers the refractive index) but alcohol has a higher refractive index than water (causing the refractive index to rise). Brewers Friend uses the Sean Terrill calculator for estimating the post fermentation gravity, but in my experience this produces some wildly inaccurate results. The problem is that most of the beers I make have high attenuation, and Sean Terrill himself admits that his calculator in inaccurate with highly attenuating beers. However, I do use my refractometer occasionally to detect when fermentation is complete. I simply take periodic Brix readings. When the Brix readings stop dropping, then fermentation is complete. If I need to know the actual FG, I take a single hydrometer reading.


Although this may seem complicated at first, it gets much easier as you get used to it. It is faster and wastes much less beer in samples, not to mention the broken hydrometers, or the effect on my blood pressure when the hydrometer settles with the scale facing in the wrong direction.


Hope this helps,


-a.
 
I only use the hydrometer three times now.
1) Just before the yeast is pitched
2) Sample 10-14 days later for an SG reading to compare in the next few days
3) A final reading to make sure gravity has not changed from the prior sample.

Hey, those are the exact same times I use my refractometer!! :D
 
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All the above deals with using a refractometer and software to estimate the specific gravity prior to fermentation. Once fermentation starts however, things get a lot more complicated.
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You almost scared ME away from using a refractometer and that's been my primary tool for many years. I've been collecting dual FG readings using hydro and refract for many batches and have found that FG readings are within my margin of error on reading either device (i.e. the FG difference is negligible between the two).

Another interesting fact (I'm sure many people are aware of) that I just became profoundly aware of is when a solution contains non-sugar solids. Hydrometers read these as gravity points while refractometers do not. I did the simple test of some corn starch in water and measured with each instrument - hydro read gravity points while refract read zero. A classic example of when your hydro might be giving you false readings is when you have unconverted starches remaining in your runnings/wort. Your hydro will tell you the "sugar" is there when in fact it is simply longer-chain carbs that will remain untouched by the yeast. This was an eye opener for me and convinces me that using a refract for prefermentation readings is very advantageous.
 
For anyone interested in the kind of differences I've been seeing in hydro to refract comparisons, you can see the overall difference in the last column in terms of "point difference" (e.g. 1.000 to 1.001 is 1 point difference).

Code:
  Sample   Temp   OG(%B)   OG(SG)   FG(%B)  FG(%B>SG)   FG(SG)   Delta
--------   ----   ------   ------   ------  ---------   ------   -----
Distilld   60.0        0        0        0          0   1.0000
     ESB   59.7     14.6    1.058      8.0      1.015   1.0145     0.5
  RedAle   59.9    13.75    1.054      6.6      1.009   1.0105     1.5
  BelgPA   60.3     14.2    1.056      7.0      1.010   1.0100       0
 CalComB   60.1       13    1.051     6.95      1.013   1.0125     0.5
 SWinSai   59.7     18.4    1.074      8.4      1.008   1.0090       1
 SSumSai   59.8     14.5    1.058      6.6      1.006   1.0070       1
BGoldStr   72.5     18.6    1.075      7.8      1.004   1.0040       0
 CreamAl     66       12    1.047      6.1      1.010   1.0105     0.5
BDarkStr   71.8     22.5    1.092     11.0      1.014   1.0150       1
 BelgIPA   60.3     16.1    1.064      7.8      1.010   1.0100       0
  VnaLgr   60.2     14.2    1.056     7.20      1.012   1.0120       0
  WLAmbr   63.7    16.75    1.067      8.9      1.016   1.0150       1
MerCrAle     60    12.75    1.050      6.0      1.008   1.0070     0.5
AltPugBr     53     13.2    1.052      6.8      1.011   1.0110       0
OatStout     60     15.4    1.061      9.9      1.026   1.0260       0
 WildWit   61.5     12.2    1.048      7.1      1.016   1.0160       0
WickMild   64.8     9.65    1.038      6.6      1.018   1.0160       2

At this point, the average is about 0.55 point difference between the hydro and refract. For most recipes, this is negligible and easily falls within the users margin of error on reading one of these tools.

BTW, I have calibrated my refractometer in both distilled and my filtered "hard" tap water, and both read zero. I also rarely recalibrate my refract (maybe 3 times in 10+ years) and each time it has read zero with distilled water. The one time I had wildly inaccurate OG readings on my refract was when I overheated the crystal with very hot wort - ATC doesn't mean it can handle ice-cold or boiling-hot samples :rolleyes:
 
Although this may seem complicated at first, it gets much easier as you get used to it. It is faster and wastes much less beer in samples...

Thanks for the thorough explanation, and believe it or not, I understand it. I only have one bone to pick with you --- in the above quote you say using a hydrometer "wastes" beer. So, far I have not wasted a drop of all the samples I have collected into my 8 oz. test jar. After testing the wort, I put the test jar in the fridge to cool and settle out, and later pour it off into a glass and enjoy. :mug:
 
Refractometers are horrible for reading the final gravity. Just saying . . .

'da Kid

I am not sure why you would say that, side by side I get within .001 between my hydrometer and my refractometer both pre and post ferment. You do have to use a calculator for Brix to SG.

If you have a dual scale you need to ignore the SG side anyway. SG scales on most hydrometers are off at high gravities, and SG scale cannot be used at all after fermentation begins.

For anyone that doesn't already have a refractometer but is looking to buy one, one buy a Brix only model like the breweries do - the scale is larger and easier to read.
 
From what I've read everyone that has checked their refractometer using both distilled and tap water has said that the difference between the 2 is virtually nil so why waste your money on distilled water if the only thing your going to use it for is to calibrate your refractometer once in a while?



If you really feel like using distilled water then bring some of your tap water to a boil, put a lid on the pot, wait until said lid collects some droplets on it, and grab those droplets with your eyedropper.


FWIW, I calibrate mine with the same water I'm brewing with. If I'm measuring the dissolved solids in my wort(which is made with my brewing water) then why would I calibrate it with different water?

I've done that and it works great for me.



- ISM NRP
 
Thanks for the thorough explanation, and believe it or not, I understand it. I only have one bone to pick with you --- in the above quote you say using a hydrometer "wastes" beer. So, far I have not wasted a drop of all the samples I have collected into my 8 oz. test jar. After testing the wort, I put the test jar in the fridge to cool and settle out, and later pour it off into a glass and enjoy. :mug:

For those who brew 5-10 gallon batches and more, the amount of beer "wasted" from hydrometer samples is insignificant. For those of us who brew "small" batches..... I brew from 1.5 - 2.5 gallons, and might be able to get away with 3, those samples add up.

I maintain that absolute readings are irrelevant for the most part unless we are absolutely trying to duplicate someone else's recipe that was measured with a hydrometer to the Tee........

Neither device measures what we want to measure......directly, which is how much sugar is in our wort........nor can we measure fermentable sugar versus non-fermentable sugar. One measures the specific gravity which clearly does NOT equate directly to sugar or alcohol content, the other measures refractive index, which also does NOT equate directly to sugar or alcohol content.

In both cases we are drawing a reasonable conclusion based on experience. The rule that I think we need to apply here is: Use a refractometer....... or a hydometer.........not both. Using both will just muddy the water (beer?) unnecessarily..........

H.W.
 
Old, but relevant post to a question I had regarding refractometer calibration. Sure hope this isn't the oldest one ever drug up from the depths!
 
"I've never calibrated with distilled water...... would never consider doing it. In theory at least, if you calibrate according to distilled water, but you brew using tap water, and you are shooting for an OG, that OG will not accurately represent the sugar content if your baseline is distilled water. "
because it establishes an agreed universal zero , not basing it on what you "might" have...
dont be cheap , go buy a gallon of DW and calibrate with it. I keep a jug around to fill my humidor humidifiers but if you dont have anything else to use it for(like , if your wife irons clothes) , dump it in your next brew. Wont hurt anything.
 
Distilled or not, no problem if the water is clean enough to not cause major refraction. The key thing is that when measuring FG with refractometer, you need to know OG and then make correction for alcohol (that strongly affects light) using calculator such as Brewersfriend. To be exact, you should also draw several samples when using refractometer and also define a wort correction factor (not related to sugar but other compounds in wort that differ from plain water-sugar solution used to calibrate the refractometer apparatus). But you'll probably come reasonably close by just calibrating with water and correcting for alcohol using the calculator. It depends on the device and how exact you need to be. But without correcting for alcohol in the sample the measurement is totally useless. An example: Yesterday, I measured a bottle of commercial Fuller's ESB and it gives 7,2 Brix in my tap water-calibrated refractometer. Knowing that the OG for this beer is 1.057 (14 P°) and using the calculator I can see that FG is about 1.012, although 7,2 Brix would correspond to 1.029 without correction for alcohol.
 
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Actually, the question was regarding whether it was better to calibrate to the actual water being used vs distilled.

Always best to use distilled. You want the ion content to be close to 0 as possible. Tap water is fine if your water is low in TDS. If you have some bad water, you shouldn't use it.
 
Thanks! Our tap water is quite low in dissolved solids, the only wrench in the works is what public works adds to make the water safe to drink out of the tap.
 

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