Question about perplexing refractometer readout

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djf123

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I bought a handheld alcohol refractometer from ebay. This model Handheld Alcohol Refractometer 0~80% With ATC Liquor Tester Meter Measuring Tool | eBay.

And I bought some denatured alcohol from Lowes. This stuff https://www.lowes.com/pd/Jasco-1-Qu...nnwl51f8ZkFnBTbz3TUaAsTeEALw_wcB&gclsrc=aw.ds.

I first calibrated the refractometer with distilled water by turning a screw on it until the blue/clear intersection was at zero. I then put a few drops of the denatured alcohol on the refractomer and got a reading of 24% alcohol. I was surprised because I was expecting to get 100% alcohol as this was supposed to be pure ethanol. I then mixed a batch of about 9 parts denatured alcohol to 1 part tap water. The solution became cloudy. I then took a reading with the refractometer with this new solution and got a reading of 34% alcohol!

What on earth is going on? How can adding just a little bit of water be making the alcohol reading go up?? I tried mixing a solution of about 9 parts tap water and 1 part denatured alchohol and finally the reading goes below 24% ( I got a reading of about 3% alcohol). Why is this happening and why is the pure denatured alcohol reading only 24%?
 

VikeMan

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I don't know what kind of refractometer that is, but I'm pretty sure there's no such thing as a refractometer that will reliably tell you the alcohol content of a beverage, at least not for beer. If there were, breweries wouldn't spend money on lab tests.
 
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doogie

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VikeMan is correct it can only tell you the amount of sugar in solution. How a refractometer works

Alcohol messes up the reading, so that you need to use a calculator to determine the final gravity when there is alcohol in the sample. I only use a refractometer on brew day (and hardly ever now) and stick to hydrometer readings for final gravity readings.
 

VikeMan

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VikeMan is correct it can only tell you the amount of sugar in solution. How a refractometer works
Well, there are "sprit refractometers" for measuring ABV of distilled products. I don't know how accurate they are, but they won't work for beer. I assume @djf123 is planning to use with beer, given the forum and sub-forum the question was posted in.
 
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djf123

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No, it's for distillation experiments, not for beer or wine making. I'm just experimenting with different distillation methods for fun at home. I'm just mixing pure denatured ethanol and tap water, distilling the solution and seeing how good of a job I can do at removing the water. I was hoping to use the refractometer to get a rough reading of the before and after alcohol content, but yikes, I had no idea that it wouldn't be anywhere near possible with that refractometer thing.

I won't be using yeast or sugar in any way to make the alcohol. I'm just buying pure lab grade ethanol, mixing it with pure water, and then distilling it to test a distilling apparatus I made.

Would a hygrometer or a "spirit refractometer" or something else be best for that? I just want to be able to tell the % alchohol content to within plus or minus 5%. I wouldn't be interested in the expense of sending it off to a lab.
 

Birrofilo

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Any refractometer should be useable to give you a direct or indirect reading of the alcohol content of a alcohol-water mixture.

You can use this same instrument, through a convertion table, to measure the sugar content of a sugar-water mixture.

For a theoretical clarification, search the internet for:
The Refractive Indices of Ethyl Alcohol and Water Mixtures.pdf
Janina Nowakowska
Loyola University Chicago - 1939

That said, I don't understand why your refractometer doesn't seem to work

Just as mere attempts to guess a solution:

a) the denaturant messes up with the refraction index of the mixture. Try it with Tequila, Grappa, neutral spirit etc. first and see if the refractometer is coherent with the alcoholmeter (or the label);

b) the light source is not the right one, i.e. the solar one, or is not the light source which you used to calibrate it. In general, those instrument need solar source. The lower the quality of the light source (the completeness of the spectrum), the most uncertain the results;

c) there is a serious quality issue with the instrument, which I think is the less likely case after all

A refractometer is a seriously comfortable instrument to give an instantaneous reading of alcohol content, and IMHO possibly better than an alcoholmeter in a parrot, if one can make precise readings. This method gives reliable results only if you know in advance that your spirit is less than 80% ABV.

One of these days I will play with different dilutions and different refractometer readings.
 
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djf123

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I mixed a pure ethanol and only added a little bit of water so the alchohol solution was very likely greater than 80%. Could that be the reason why it behaved the way it did? I calibrated it indoors using just standard LED light bulbs in the room. All measurements were done in that same room with the same light source and were taken and calibrated at 68 degrees F.
 

VikeMan

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I mixed a pure ethanol and only added a little bit of water so the alchohol solution was very likely greater than 80%. Could that be the reason why it behaved the way it did?
FWIW, Denatured Alcohol ≠ Pure Ethanol
 

Birrofilo

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I mixed a pure ethanol and only added a little bit of water so the alchohol solution was very likely greater than 80%. Could that be the reason why it behaved the way it did? I calibrated it indoors using just standard LED light bulbs in the room. All measurements were done in that same room with the same light source and were taken and calibrated at 68 degrees F.
The reason why the refractometer gives a reading up to 80% is that the refractive index of an ethanol-water solution reaches a maximum at 82,86% ABV (RI 1,3649) and then decreases again, so that if your refractometer reads 1,3637 this might indicate 92,68% ABV or a little more than 60% ABV.
 

moorejl57

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The reason why the refractometer gives a reading up to 80% is that the refractive index of an ethanol-water solution reaches a maximum at 82,86% ABV (RI 1,3649) and then decreases again, so that if your refractometer reads 1,3637 this might indicate 92,68% ABV or a little more than 60% ABV.
Yes this ^. If you want to use your refractometer to measure high proof ethanol solutions, the standard practice is to first dilute 50/50 with distilled water. It has a non linear response so it is not very accurate over 60%. By diluting your sample, you get into a useful measurement range. If the sample is already < 60%, no need to dilute.
 

jseyfert3

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And I bought some denatured alcohol from Lowes. This stuff https://www.lowes.com/pd/Jasco-1-Qu...nnwl51f8ZkFnBTbz3TUaAsTeEALw_wcB&gclsrc=aw.ds.

I first calibrated the refractometer with distilled water by turning a screw on it until the blue/clear intersection was at zero. I then put a few drops of the denatured alcohol on the refractomer and got a reading of 24% alcohol. I was surprised because I was expecting to get 100% alcohol as this was supposed to be pure ethanol. I then mixed a batch of about 9 parts denatured alcohol to 1 part tap water. The solution became cloudy. I then took a reading with the refractometer with this new solution and got a reading of 34% alcohol!
FWIW, Denatured Alcohol ≠ Pure Ethanol
^This^

Specifically the denatured alcohol the OP linked is only 30-50% ethanol, the rest methanol along with up to 1% Methyl isobutyl ketone.
3A3BEEAB-EB3D-47E9-8EC7-68ED951D7E62.png
 

Birrofilo

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I still have to make two stripping runs and finally I want to make a neutral spirit run with the reflux still.

Then, I want to do a simple table.

I have the spirit which is let's say 95% ABV. I note the reading of the alcoholmeter and I note the reading of the refractometer (my one talks °Brix).
Then I dilute a little bit, and repeat both measures, and note them.
Then I dilute a little bit...

After an afternoon I should have a pretty decent table.

@moorejl57 Your advice to dilute 50-50 is very sensible, not just to avoid the ambiguity but also to bring the refractometer to work in a value range where it might be more comfortable.

The idea is to use the refractometer during a run as a parrot, but without the smearing and the delayed result of a parrot.
 

jseyfert3

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Adding on to my previous post, water has a refractive index of 1.333. Ethanol is 1.361. Methanol is 1.331. And methyl isobutyl ketone is 1.396.

In all cases a methanol/water mix has a refractive index well below any ethanol/water mix, so I’m assuming a roughly 50/50 mix of methanol and ethanol is what’s skewing the reading so low.

Oh, and unlike methanol and ethanol, both of which are soluble in water in any percentages, methyl isobutyl ketone is not very soluble in water which is probably why the denatured alcohol is going cloudy when mixed with water. Or at least that’s my guess.

Try getting some 190 proof Everclear and trying the diluted water/alcohol mix again.
 

moorejl57

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I don't know what kind of refractometer that is, but I'm pretty sure there's no such thing as a refractometer that will reliably tell you the alcohol content of a beverage, at least not for beer. If there were, breweries wouldn't spend money on lab tests.
When I first bought my refractometer calibrated for Brix, I believed it was only able to measure sucrose solutions. Then my niece asked to borrow it to measure the salt level in her aquarium. Then reading posts on home distilling forums, I learned you can measure alcohol levels. Then finally on the coffee forums I learned you can measure TDS (total dissolved solids) lol. As it turns out, which should have been obvious to me, it measures the refractive index of whatever you put into it and you can make a table or equation to covert your readings from the Brix scale.

I agree it is not accurate enough for a distillery to use.
 

bernardsmith

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But you actually explained WHY a refractometer cannot accurately inform you of the alcohol level. It measures the refractive index of dissolved solids in water. Water and not alcohol. Light bends at a different angle (refraction) when it travels through water than when it travels through alcohol and so if you are trying to measure the amount of dissolved sugar in a mixture of alcohol and water (which is what you are in fact measuring and NOT the actual amount of alcohol) then the angle the light is refracted at is going to be different in different percentages of water AND alcohol in a single solution.

And this is preciely why you CAN use a refractometer when you squeeze a drop of juice on the glass to measure how much sugar is in the fruit (the liquid is water and the solids dissolved in that water are fructose or sucrose or some other sugar) and why you CAN use this tool when you take a drop of the must and place it on the glass (the liquid is, again only water and the dissolved solids are sugar), but you CANNOT use a refractometer without complex calculations when you have pitched yeast and the yeast have transformed some of the sugar into alcohol - the dissolved solids are still sugar but you now have added ethanol to the water.
 

bruce_the_loon

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The best way for measure alcohol in distillates would be to get a hydrometer that has a proof scale. See photo below. This is what distillers use letting it float in the outflow from the still. Search the internet for alcohol meter or proof scale hydrometer.

Hydrometer-Alcohol-0-200-Proof-and-Tralle-1.jpg
 

bernardsmith

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But does a proof hydrometer accurately measure the alcohol in a solution that includes both sugar and alcohol? If you had a vodka that was 40 proof (20% ABV) and you added sugar what would the reading show?
 

jseyfert3

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But you actually explained WHY a refractometer cannot accurately inform you of the alcohol level. It measures the refractive index of dissolved solids in water. Water and not alcohol. Light bends at a different angle (refraction) when it travels through water than when it travels through alcohol and so if you are trying to measure the amount of dissolved sugar in a mixture of alcohol and water (which is what you are in fact measuring and NOT the actual amount of alcohol) then the angle the light is refracted at is going to be different in different percentages of water AND alcohol in a single solution.

And this is preciely why you CAN use a refractometer when you squeeze a drop of juice on the glass to measure how much sugar is in the fruit (the liquid is water and the solids dissolved in that water are fructose or sucrose or some other sugar) and why you CAN use this tool when you take a drop of the must and place it on the glass (the liquid is, again only water and the dissolved solids are sugar), but you CANNOT use a refractometer without complex calculations when you have pitched yeast and the yeast have transformed some of the sugar into alcohol - the dissolved solids are still sugar but you now have added ethanol to the water.
In an ethanol/water/sugar solution, yes. But if distilling, like the OP, the distillate should be just an ethanol/water mix with no sugar, which could indeed be measured with a refractometer, per the PDF @Birrofilo mentioned. At least until ~53%, after which the curve of refractive index bends over and your measurement leads to two different possible ABV readings, though within reason this range can be extended upwards a bit.

But does a proof hydrometer accurately measure the alcohol in a solution that includes both sugar and alcohol? If you had a vodka that was 40 proof (20% ABV) and you added sugar what would the reading show?
I don't think it would, but distillate would not contain both sugar and alcohol, so a hydrometer should work just fine. Now I'm curious and I'll have to look up the origin of the common ABV = 131.25*(IG - FG). I assume this equation corrects for the presence of sugar, at least over some particular range...
 

bernardsmith

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But an hydrometer is simply measuring the density of a liquid compared to water. That density can be caused by salt, sugar, dirt, anti-freeze, honey or flour. The key point is only that the liquid must be water. The algorithm of 131.25 converts the density (assuming caused by sugar) and the change in density caused by alcohol (being less dense than water) to a fair approximation of the alcohol by volume content of this solution. So, a drop of 90 points (.090) would amount to about 12% alcohol by volume and a drop of 45 points (.045) would amount to about 6% ABV. There may or not be any sugar remaining. This is just a calculation based on the initial gravity (density) of a solution of sugar and water minus the final gravity of the same liquid now with less (or no sugar and some ethanol) . We KNOW the change in density and when we apply that multiplier of 131.25 this converts that known change into an approximation for the amount of alcohol that is in the solution whether or not there is some or no sugar remaining because (I think) it is based NOT on a specific reading per se but in the amount of the drop from the initial reading to the reading now. In other words, we ignore the ACTUAL reading (a reading from 1.100 to 1.090 is 10 points as is a reading that began at 1.050 and dropped to 1.040 - very different actual readings).
 

Birrofilo

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A refractometer can measure anything where you can draw a relationship - a first grade equation - between two variables.

Y = aX + k

If X is the only variable, and you have a law connecting all values of X to a value of Y, by measuring X you know Y.

We have this law for a water-sugar solution (each concentration will give a certain refractive index), for alcohol-water solution (same as above although here we have a Y = aX^2 + k, and we have two solutions), water-salt solution, and probably this could be repeated with any two liquid mescible things, e.g. water-glicerine, sugar-alcohol, or water-Johnny Walker red label, or water-Coke, or water-Limoncello.

If you know that your mixture is water-Coke, and you draw a table with the various RI corresponding to each coke percentage, by measuring the RI of a water-Coke mixture you can know how much Coke is in there.

The problem with beer is that we don't have any more a alcohol-water solution or a water-sugar solution or a sugar-alcohol solution, but we have a water-sugar-alcohol solution and we don't know how much of each.

We have a Y = aX + bZ + k equation. For each Y (RI) we have an infinite number of couplet solutions. A certain value of Y (a certain RI read by the instrument) can correspond to a solution with more alcohol and less sugar or less alcohol and more sugar for instance.

If we knew exactly a proportion, such as the sugar-alcohol proportion, then we could again draw a table. In the example above, if we have a certain known Limoncello, and we dilute it with water and for each dilution we measure the RI, then when we have a solution which we know is exactly that Limoncello with some water, the RI will give us the exact concentration of that Limoncello in the water.

Ultimately the only thing that the refractometer can tell us is the refractive index of a solution. The same refractometer can measure the saltiness of the water, the ABV of an alcohol-water mixture, or the sweetness of a sugar-water mixture, or anything for which we can write a table.

Incidentally, sometimes I read that a refractometer should always be used in °Brix and not in density points, because the relationship between °B and density points is not linear, or that, when a refractometer has both scales, only the °B is reliable.

True it is not linear, but that doesn't disturb the refractometer at all. For each RI there is a density value which is both a certain °B and a certain absolute density measure. Both scales are itched on your instrument in the right places. They are precise in the same way.
 
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jseyfert3

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But an hydrometer is simply measuring the density of a liquid compared to water. That density can be caused by salt, sugar, dirt, anti-freeze, honey or flour. The key point is only that the liquid must be water. The algorithm of 131.25 converts the density (assuming caused by sugar) and the change in density caused by alcohol (being less dense than water) to a fair approximation of the alcohol by volume content of this solution. So, a drop of 90 points (.090) would amount to about 12% alcohol by volume and a drop of 45 points (.045) would amount to about 6% ABV. There may or not be any sugar remaining. This is just a calculation based on the initial gravity (density) of a solution of sugar and water minus the final gravity of the same liquid now with less (or no sugar and some ethanol) . We KNOW the change in density and when we apply that multiplier of 131.25 this converts that known change into an approximation for the amount of alcohol that is in the solution whether or not there is some or no sugar remaining because (I think) it is based NOT on a specific reading per se but in the amount of the drop from the initial reading to the reading now. In other words, we ignore the ACTUAL reading (a reading from 1.100 to 1.090 is 10 points as is a reading that began at 1.050 and dropped to 1.040 - very different actual readings).
I agree with most of this, though I plan on plotting some stuff in Excel. I think that will illustrate where the 131.25 came from very nicely.

However, it doesn't have to be water you are measuring with a hydrometer. A hydrometer can give your the SG of any liquid, assuming the SG is within range of the hydrometer of course. For example, the acid/water solution in my Trojan T-105 deep cycle batteries changes from a SG of 1.277 when fully charged down to 1.073 when at 10% capacity. The capacity of a lead acid battery is most accurately checked by the use of a hydrometer. Okay, maybe not the best example, given that that's an acid/water mix. But take pure ethanol. It has a specific gravity of 0.789, which can certainly be measured with a hydrometer of the proper range.

So measuring the ABV of a solution known to be only ethanol and water (as the results from distilling a fermented beverage would be, ignoring minute quantities of methanol and fusel alcohols) is easily done with a hydrometer and some simple math. In fact I've worked this out just now. For a solution known to be only ethanol and water, the formula is:

ABV = (1 - SG)/0.211

I can post my math later, but if you put any SG into the above formula between 1 (pure water) and 0.789 (pure ethanol) it will output an ABV between 0 and 100%.

Bottom line is that for a water/ethanol solution (with nothing else) it is very simple and easy to measure ABV with a hydrometer.
 
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