Tool to measure abv?

[bracconiere]

yeah, i know when alcohol is present refractometers don't work for a FG reading...that why comparing a refractometer FG reading to a hydrometer one will let you figure out how much alcohol is present? or so i've over heard people's text saying so.....and i've seen calculator that calculate it, better then the quick one i posted....


edit: damn, at this point i need proof....i'm going to order a refractometer off ebay, and try it out on a batch...see if the calcs work....

 

[Birrofilo]

yeah, i know when alcohol is present refractometers don't work for a FG reading...that why comparing a refractometer FG reading to a hydrometer one will let you figure out how much alcohol is present? or so i've over heard people's text saying so.....and i've seen calculator that calculate it, better then the quick one i posted....

If you took the OG gravity, before fermentation, of that beer, you can use the refractometer to know the FG of that beer, which in turn allows you to calculate how much alcohol there is.

Comparing the refractometer FG reading to a hydrometer will not tell you how much alcohol there is, nor the refractometer reading will tell you that, nor the hydrometer reading.

What can be said is that comparing the refractometer reading (FG) with the hydrometer reading of the OG will allow you to know the alcohol in the beer. But that will work also if the OG is obtained with a refractometer instead of a hydrometer, the hydrometer being more precise though.

You need OG and FG to know ABV and it doesn't matter if you measure them with the hydrometer or the refractometer. You don't need a hydrometer to measure OG and FG and to calculate ABV.

 

[bracconiere]

If you took the OG gravity, before fermentation, of that beer, you can use the refractometer to know the FG of that beer, which in turn allows you to calculate how much alcohol there is.

Comparing the refractometer FG reading to a hydrometer will not tell you how much alcohol there is, nor the refractometer reading will tell you that, nor the hydrometer reading.

What can be said is that comparing the refractometer reading (FG) with the hydrometer reading of the OG will allow you to know the alcohol in the beer. But that will work also if the OG is obtained with a refractometer instead of a hydrometer, the hydrometer being more precise though.

You need OG and FG to know ABV and it doesn't matter if you measure them with the hydrometer or the refractometer. You don't need a hydrometer to measure OG and FG and to calculate ABV.

dude, i've seen calcs...and i've heard people talk...being that a refractometer will read difrently with alcohol present then a hydrometer...you can punch both the number into a calc and figure ABV & what the og was.......kinda like using the tan thing on a spiffy calculator to figure the angle, or how long a side of a right triangle is.....

 

[Qhrumphf]

What he's saying is the formulas have three variables- actual FG, refractometer FG, and OG. By knowing two of three you can derive the third. If you have the real FG via hydrometer AND the refractometer FG, you can reverse engineer the OG, as well as the ABV.

But that still isn't relevant for when the ethanol has been removed as the OP was originally asking.

 

[Birrofilo]

What he's saying is the formulas have three variables- actual FG, refractometer FG, and OG. By knowing two of three you can derive the third. If you have the real FG via hydrometer AND the refractometer FG, you can reverse engineer the OG, as well as the ABV.

But that still isn't relevant for when the ethanol has been removed as the OP was originally asking.

If "he" is myself, I am not saying that.

You can know ABV if:

You have a hydrometer, and with that you measure OG and FG, and then you calculate ABV;

OR

You have a refractometer, and with that you measure OG and FG, and then you calculate ABV;

There is no difference between refractometer OG and hydrometer OG besides hydrometer OG being more precise.

There is no difference between refractometer FG and hydrometer FG, besides refractometer FG needing an OG measure to have been made beforehand, either with a refractometer or a hydrometer, but a bloody OG is needed if you want to measure FG with a refractometer; that's not needed if you want to measure FG with a hydrometer.

And one needs an OG and a FG to calculate ABV, you cannot calculate ABV if you don't know both, and the instrument used to measure OG and FG is totally irrelevant in the calculation of ABV.

Maybe I should improve my English skills.

 

[Qhrumphf]

No, "he" wasn't you.

Nvotony's equations (which the Brewers Friend calculator uses) use various factors and constants to manipulate three variables. Brix OG, Brix refractometer FG, and real corrected FG.

If you measure the real FG with a hydrometer, and also measure the FG with a refractometer, you can algebraically manipulate the equation and get the OG.

http://www.diversity.beer/2017/01/pocitame-nova-korekce-refraktometru.html?m=1

 

[Qhrumphf]

(there should be an english version in Zymurgy from a few years ago)

 

[bracconiere]

so i'm not crazy? (or just plain wrong? lol) you might not be able to calculate OG if the alcohol was removed, but why not ABV?

would you need a different formula like compared to a sine or cosine?

 

[Birrofilo]

so i'm not crazy? (or just plain wrong? lol) you might not be able to calculate OG if the alcohol was removed, but why not ABV?

would you need a different formula like compared to a sine or cosine?

Dude, either you are a poacher, as your nickname implies, or you drink too much beer, or my English is really deprived of clarity and I should begin from page one, which is entirely possible. And I do hope you are not a poacher although crazy I cannot tell (and the Pope would say: who am I to say you are crazy? And I am not even Catholic.)

The problem with ABV calculation of a beer where alcohol was removed, is that because of the removal of alcohol, the original equations which allowed you to arrive to an acceptable estimate of the quantity of alcohol present in your alcoholic beverage do not apply anymore once the original balance between gravity, unfermented sugars and fermented sugar is altered by the above mentioned alcohol removal.

In the case of OG alcohol never was present, because by what might be termed as a definition, OG or Original Gravity is a density taken before fermentation has even had the slightest occasion to start, and the brew which is the subject of the density analysis is therefore deprived of alcohol in both theory and practice.

 

[bracconiere]

or my English is really deprived of clarity

no man, you're speaking clearer text then i do in english....i think hydroemeters measure density, and refractometers measure viscosity. or something like that....comparing the two you can figure how much alcohol is present?

 

[Birrofilo]

Before I get too tired (it's 3:25 here) I have an idea which might be interesting for the OP.

IF your process is clearly repeatable, you could:

a) Make 10 samples of 10 different degrees of alcohol reduction;
b) Make accurate measuring of whatever parameter you find differentiating enough: refraction index with a refractometer, gravity with a hydrometer in the proper density range, or anything else like weight (with one of those scales that go to the 1000th of gram and that actually work), colour, whatever you have an instrument for.
c) Give those 10 samples to a laboratory for a serious and precise alcohol content response using the most precise method they can;
d) Make a table of the 10 ABV values the laboratory gave you and the 10 values that you observed at home.

If they make a nice curve, or even better a nice line on a graph, then you don't need to send any more sample to the lab.

For each beer you make, you can measure your own value and relate it to the table.

The problem here is "repeatability" of course. You could postpone this until you have a recipe that you can brew with good uniformity, and a measuring method that you have nailed down with sufficient accuracy.

If a hydrometer or a refractometer differentiate enough your samples at different ABV, you can pay the lab only once.

 

[RufusBrewer]

Ultimately unless you're incredibly accurate in your volume reading of your distillate, which if I understand correctly is the most critical error point, how you accurately measure the density thereafter depends on that first accuracy anyway. The method I saw derived ABW from the weight of distillate and then calculated ABV from there.

I haven't had a chance to try it hands on yet but it's on my to do list.

Wouldn't accurate measurement of the starting volume be critical as well. You could measure X grams of distillate or Y liters of distillate, dead nuts accurate. It would be of marginal value unless you knew you drew that from Z liters of beer with an X.Y% ABV.

 

[bracconiere]

i thought the refractometer reading compared to a hydrometer reading was good enough? now i'm wondering?

damn, at this point i need proof....i'm going to order a refractometer off ebay, and try it out on a batch...see if the calcs work....

well, i got my refractometer. and i've been f'n around with it comparing it to hydrometer readings...so far the calcs all work....i tested a known batch of beer, whiskey and water.....the calcs co-incide with my measurements for how much ABV they have.....handy trick


as an update to the thread...

 

[rushpapers]

Just take a second FG reading after de-alcoholizing and calculate the % drop.

What's the problem?

 

[DuncB]

Send a sample in a blood tube to the local blood lab and they will tell you the alcohol amount in mg/ litre.

 

[rushpapers]

If you don't have an OG it's a problem

If you do have OG it is pretty damn simple.

A refractometer measures brix of a liquid based on how light bends or the "refraction" through a liquid.

Hydrometer measures the density of liquids.

 

[Vale71]

OK I'll bite.

OG: 12°Brix
FG before ethanol removal: 8.5°Brix
FG after ethanol removal: 6°Brix

What is the ABV after alcohol removal?

 

[VikeMan]

Just take a second FG reading after de-alcoholizing and calculate the % drop.

What's the problem?

What formula do you propose to do this? You can use the data in post #47 as an example if you don't mind.

 

[Smiling Frog]

OK I'll bite.

OG: 12°Brix
FG before ethanol removal: 8.5°Brix
FG after ethanol removal: 6°Brix

What is the ABV after alcohol removal?

Where did you get these numbers?

Assuming none of the dissolved solids are removed when the alcohol is removed (that is, only alcohol and water is removed), the SG should go up, not down. If you are getting a lower SG after you removed the alcohol, you have removed a lot of the dissolved solids (roughly, 21% of the remaining sugars : 1.5/8.5= 0.21)

 

[bracconiere]

OK I'll bite.

OG: 12°Brix
FG before ethanol removal: 8.5°Brix
FG after ethanol removal: 6°Brix

What is the ABV after alcohol removal?

i just punched 6 brix and a guess at what a hydrometer reading would be of 1.019...(assuming a bit higher with alcohol removed)


and i get 1.6%ABV

 

[rushpapers]

The example given is incorrect, it's like saying your gas tank will have more fuel after driving 300 miles.

It would be like this.

OG: 1.060/14 Brix
FG: 1.010/2.6 Brix

ABV 6.67%

New FG after de-alcoholizing: 1.030 7.6 Brix

New ABV 4.0%

 

[Vale71]

Except ethanol will actually cause a refractometer reading to increase compared to the actual value, which is why you need a correction formula.

It follows that if you were to remove ethanol from the mixture the refactometer reading would actually decrease but if you were to apply the same correction formula you would get a false, higher calculated ABV value.

See, it's not as simple as you think. Unless you have no idea about how something actually works, then everything is easy-peasy...

 

[Vale71]

Where did you get these numbers?

Assuming none of the dissolved solids are removed when the alcohol is removed (that is, only alcohol and water is removed), the SG should go up, not down. If you are getting a lower SG after you removed the alcohol, you have removed a lot of the dissolved solids (roughly, 21% of the remaining sugars : 1.5/8.5= 0.21)

See previous post.

 

[VikeMan]

Except ethanol will actually cause a refractometer reading to increase compared to the actual value, which is why you need a correction formula.

It follows that if you were to remove ethanol from the mixture the refactometer reading would actually decrease but if you were to apply the same correction formula you would get a false, higher calculated ABV value.

This is the correct answer. Since it has now been mentioned in various ways at least 3 times in this thread, perhaps it will stick.

 

[rushpapers]

Yes it is that easy.

Use a hydrometer. I never said use a refractometer.

If you take away alcohol (ethanol, isopropyl, etc.) from the solution of beer, and nothing else, the beer will become more dense.

It's simple high school chemistry.

 

[Vale71]

That's what was being discussed so it was natural to assume you were talking about refractometer readings as well.

Even with a hydrometer it's not that easy. If you hold your beer at those temperatures for quite some time there will be some water evaporating as well and that will affect the outcome. Unless you want to start calculating differential water/ethanol evaporation rates the accuracy of the calculated value will suffer.

Then there's all that wasted beer if you have to take repeated measurements to determine when a certain ABV threshold has been crossed. If only actual densitometers weren't that expensive...

 

[Birrofilo]

If you take away alcohol (ethanol, isopropyl, etc.) from the solution of beer, and nothing else, the beer will become more dense.

A hydrometer only tells you density. Alcohol content is always the result of a calculation which is possible only because of the fixed relation between the gravity (sugar) that is missing and the alcohol which is produced when that quantity of missing sugar is consumed.

We estimate alcohol because we measure OG, subtract FG, which means we know how much sugar was converted into alcohol and CO2. It's only the missing sugar which tells us the alcohol in the liquid, not the density.

To make an extreme example, a hydrometer can tell you the density is 1,012 and this could be a final gravity (alcohol present) or an original gravity (no alcohol present). The hydrometer doesn't know about the fermentation and cannot be used to evaluate alcohol.

If you use the new FG after de-alcoholizing and compare that with the original OG, you don't have any more a correct relationship between OG and FG that can give you the sugar missing, hence the alcohol in the beer.

This is a problem which is similar to infering density with a refractometer if alcohol is present.
If you have a mixture with three substances (water, sugar, alcohol) you cannot use a hydrometer or a refractometer to arrive to the direct determination of each substance.

You could do that only if there are two substances in a liquid because in that case you can "draw a table".

 

[rushpapers]

...and we know the effects of sugar and alcohol on the density of liquids. If we have our numbers we can calculate changes.

If you want to bang your heads against the wall, by all means.

You take alcohol away, you then have a new FG to calculate with.

It's that simple.

I could understand this being difficult if the OG was unknown.

And a refractometer would work as well.

 

[VikeMan]

Yes it is that easy.

Use a hydrometer. I never said use a refractometer.

If you take away alcohol (ethanol, isopropyl, etc.) from the solution of beer, and nothing else, the beer will become more dense.

It's simple high school chemistry.

The standard hydrometer ABV formulae rely on an underlying assumption about how much ethanol (which is less dense than water) is made per mass of extract lost. If you remove alcohol without putting the extract back, you've broken the underlying assumption.

 

[VikeMan]

And a refractometer would work as well.

No, as @Vale explained pretty clearly in post #52.