Set-up to measure ABV% of ice-concentrated beer

[EDR83]

Ok, just wanted to sense check something.

I'm thinking of building a set-up as explained on this page:

http://www.themadfermentationist.com/2009/07/testing-alcohol-content-of-ice.html

It's just that I don't want to spend all the $ buying a density meter. Therefore I thought it should be possible to weigh the final product and use this conversion table:

http://www.handymath.com/cgi-bin/ethanolwater3.cgi?submit=Entry

This gives w/w, which can then be converted to w/v using the conversion table below.

http://www.pharmcoaaper.com/pages/T...le_wt_vol_percent_ethyl_alcohol_water_mix.pdf

Just wanted to sense-check this method before I invest. Anyone any experience with anything similar? Why would or wouldn't this method work? Any additional tips?

Thanks!

 

[DaNewf]

I've never tried this myself (ice concentration) but would applying

Ci x Vi = Cf x Vf

work in this case?

Ci = initial concentration (or ABV in this case)
Vi = initial volume
Cf = final concentartion (or ABV in this case)
Vf = final volume

For example 5 litres of 5% concentated down to 3 litres:

Solve the equation for Cf:

Cf = (Ci x Vi) / Vf

Plug in the values for Ci, Vi and Vf:

Cf = (0.05 x 5) / 3 ~= 0.083 or 8.3%

It's been a long time since I took any chemistry classes but I think that's right. I hope so because I used this formula to calculate the final ABV of my wine after topping off with water after stabilizing the last batch I made.

This might not get you the exact ABV but if you did a decent job concentrating the beer it should be in the ball park.

Anyone see anything wrong with my line of reasoning?

 

[EDR83]

Thanks for the reply!

In theory that works if the method would be perfect (i.e. no beer stays behind in the ice). Unfortunately this is not the case. Especially when aiming for high ABV% with multiple iterations of freezing this is hard to avoid. For that reason I'm looking for a more exact method to work out the ABV%.

I may just try out the method described above and test using beer with known ABV%

 

[ArkotRamathorn]

I know asking the question "why do you want to do this" on a forum for homebrewing beer is very dumb question. But I would have to ask why, or more like, how accurate are you talking about?

Are you talking about being able to get it down to .01 accuracy? Or just .1 accuracy? I guess when I think about doing an ice barleywine this winter, I'll start with 5 gallons of (hopefully) 10% beer, and if I ice it down and get 2.5 gallons (haven't iced before so I am curious what my final volumes will be) then I figure I have roundabout 20% abv beer. If its actually 19% or 21% what difference in the end is there(everyone will be super super drunk after a glass of it either way)?

Like I said though its a completely nonsense question to ask why on this forum. If you are concerned with .01 accuracy though I'd bet thats gonna get expensive fast, I would just take hydrometer samples pre and post ice, if your beer had a final gravity of 1.020 and after icing you get 1.040 I'm sure theres some calculators out there somewhere that would tell you how much water was removed during the icing.

 

[ajdelange]

Ok, just wanted to sense check something.

I'm thinking of building a set-up as explained on this page:

http://www.themadfermentationist.com/2009/07/testing-alcohol-content-of-ice.html

It's just that I don't want to spend all the $ buying a density meter.

No, you'd have to be as loony as that guy Tonsmeier visited.

Therefore I thought it should be possible to weigh the final product and use this conversion table:

http://www.handymath.com/cgi-bin/ethanolwater3.cgi?submit=Entry

Well you can weigh things to get the answer (thus replacing the cost of the densitometer with the cost of a good laboratory balance and a pycnometer) and you will use a table like that one but you must weigh the distillate, not the beer (final product) to get the alcohol content. To do this with a pycnometer (a bottle which can be filled to exactly the same volume, even though the volume is not exactly known) you first tare the bottle, then fill it with DI water at 20 °C, then with the distillate, collected as in the web article you referenced. The weighings are corrected for air density and the ratio of the distillate to water weights is the specific gravity of the distillate. This is converted to density (multiply by the density of water at 20 °C) and then enter your table to get ABW or ABV depending on which table you have. Convert to ABV if your table gives ABW.

Just wanted to sense-check this method before I invest. Anyone any experience with anything similar? Why would or wouldn't this method work? Any additional tips?

Yes, it is a valid method. It is time consuming and requires meticulous procedure with respect to the pycnometer weighings. You still need the distillation apparatus, the volumetric flasks and a water bath for precise volume determinations is nice to have.

Under the additional tips" measuring the specific gravity of the beer and the residue left in the distilling flask will enable you to determine true extract, true attenuation and back calculate the original gravity.

 

[feinbera]

Another dumb question....... isn't a hydrometer a density meter? I know our beer hydrometers only go to 0.990 or so, but, there must be similarly-priced ones with scales more appropriate for use in the distilling industry.

 

[ajdelange]

Another dumb question....... isn't a hydrometer a density meter?

Not a dumb question at all!

I know our beer hydrometers only go to 0.990 or so, but, there must be similarly-priced ones with scales more appropriate for use in the distilling industry.

There are indeed. It is called a 'Tralle hydrometer' and is designed for exactly this purpose. The catch in using those for beer distillate can be seen by examining the ABV or ABW vs density tables (or the scale of a Tralle hydrometer if you have one). It takes quite a bit of alcohol content to get the specific gravity of a solution much different from 1. Thus, on the stem of a Tralle hydrometer, the numbers for the alcohol contents we would expect from beer are all bunched together. You can see this if you do a search on 'Tralle Hydrometer' and look carefully at the pictures. With sprits these things work just fine and are marginal with wine and eis beers.

 

[pdxal]

This article has a nice chart to roughly calculate alcohol content. Much easier.
The amount of concentration possible is actually more dependent upon temperature than on the amount of volume that you reduce, since the ice removed isn't pure water but has some degree of alcohol trapped in it:

http://www.popsci.com/science/article/2013-01/beersci-how-make-strong-beer-stronger

 

[EDR83]

I know asking the question "why do you want to do this" on a forum for homebrewing beer is very dumb question. But I would have to ask why, or more like, how accurate are you talking about?

Not dumb at all! Actually, I can't really give you a rational answer. It's just that I'd like to know what the exact ABV% is (and I think that judging just by volume means your likely to be a few % off)

Well you can weigh things to get the answer (thus replacing the cost of the densitometer with the cost of a good laboratory balance and a pycnometer) and you will use a table like that one but you must weigh the distillate, not the beer (final product) to get the alcohol content. To do this with a pycnometer (a bottle which can be filled to exactly the same volume, even though the volume is not exactly known) you first tare the bottle, then fill it with DI water at 20 °C, then with the distillate, collected as in the web article you referenced. The weighings are corrected for air density and the ratio of the distillate to water weights is the specific gravity of the distillate. This is converted to density (multiply by the density of water at 20 °C) and then enter your table to get ABW or ABV depending on which table you have. Convert to ABV if your table gives ABW.

Many thanks for your detailed reply!! nestar:

Quick question: isn't the pycnometer a nice-to-have? If you make sure to top up the distillate to exactly 100ml (or whatever volume, as long as you know what it is) with DI water you should be able to do this without the pycnometer, no?

Will defo give this method a go and report back if I were able to make it work.

 

[EDR83]

This article has a nice chart to roughly calculate alcohol content. Much easier.
The amount of concentration possible is actually more dependent upon temperature than on the amount of volume that you reduce, since the ice removed isn't pure water but has some degree of alcohol trapped in it:

http://www.popsci.com/science/article/2013-01/beersci-how-make-strong-beer-stronger

Are you referring to the water-ethanol phase diagram? Don't think that would give me what I need mate. It's a good diagram to figure out how far you can go with fractional freezing though! I have a ****ty freezer so probably not very far

 

[ajdelange]

Quick question: isn't the pycnometer a nice-to-have? If you make sure to top up the distillate to exactly 100ml (or whatever volume, as long as you know what it is) with DI water you should be able to do this without the pycnometer, no?

A pycnometer is, in the last analysis, just a volumetric flask so can you do it with a volumetric flask? Yes. The early ones intended for brewing were indeed volumetric flasks but with extended, extra narrow necks to make it easier to precisely refill to exactly the same level. A modern pycnometer looks more like this: http://www.gogenlab.com/products/kimax-r-pycnometer-specific-gravity-bottles-serialized. To use these chilled, decarbonated (and that can be a bit of a trick) beer or water or residue or distilled water is filled into the bottle and the 'top' which includes the thermometer inserted. This displaces fluid up through the side arm. The thing is then rinsed with DI water and wiped and left out on the bench. As time passes the residual external water dries and the bottle warms. As it does so the fluid expands and so some escapes through the side arm. This is carefully wiped away so that none runs down onto the arm. The thermometer is monitored and when it reaches 20 °C (or whatever temperature you want to know the density at) a final wipe is give and the cap put on the side arm. You have now trapped a rather precisely reproducible volume of fluid at a well known temperature and can weigh the bottle, deduct the tare and compare to the weighing of distilled water to obtain SG. The huge advantage of this type of pycnometer is that no water bath is required. The thing may cost nearly $200 but a water bath costs a lot more than that and you still need, at least, a class A volumetric flask.

If you use one of the more volumetric flask-like designs it is and you must further concern yourself with removing water from the exterior of the bottle before weighing.

Will defo give this method a go and report back if I were able to make it work.

You might want to have a look at Section 5.1 of the notes at http://wetnewf.org/pdfs/Brewing_articles/Sugar_Gravity.pdf
for the math necessary to convert pycnometer readings to density and/or specific gravity, in particular how to correct the readings for air.

 

[EDR83]

A pycnometer is, in the last analysis, just a volumetric flask so can you do it with a volumetric flask? Yes. The early ones intended for brewing were indeed volumetric flasks but with extended, extra narrow necks to make it easier to precisely refill to exactly the same level. A modern pycnometer looks more like this: http://www.gogenlab.com/products/kimax-r-pycnometer-specific-gravity-bottles-serialized. To use these chilled, decarbonated (and that can be a bit of a trick) beer or water or residue or distilled water is filled into the bottle and the 'top' which includes the thermometer inserted. This displaces fluid up through the side arm. The thing is then rinsed with DI water and wiped and left out on the bench. As time passes the residual external water dries and the bottle warms. As it does so the fluid expands and so some escapes through the side arm. This is carefully wiped away so that none runs down onto the arm. The thermometer is monitored and when it reaches 20 °C (or whatever temperature you want to know the density at) a final wipe is give and the cap put on the side arm. You have now trapped a rather precisely reproducible volume of fluid at a well known temperature and can weigh the bottle, deduct the tare and compare to the weighing of distilled water to obtain SG. The huge advantage of this type of pycnometer is that no water bath is required. The thing may cost nearly $200 but a water bath costs a lot more than that and you still need, at least, a class A volumetric flask.

If you use one of the more volumetric flask-like designs it is and you must further concern yourself with removing water from the exterior of the bottle before weighing.

You might want to have a look at Section 5.1 of the notes at http://wetnewf.org/pdfs/Brewing_articles/Sugar_Gravity.pdf
for the math necessary to convert pycnometer readings to density and/or specific gravity, in particular how to correct the readings for air.

Many thanks! You're a star! All clear

 

[DuckiesRevenge]

I'm sure there are many issues with what I'm going to propose but....

What if you took a refractometer reading and a hydrometer reading. With these two measures I have calculated OG fairly accurately a number of times. Based on this observation I would guess that the concentrated beer would have a hypothetical OG where you could calculate abv from theoretical OG and actual fg.

I think this may work since the refractometer is impacted by the presence of alcohol.

But like I mentioned before there may be factors I'm overlooking. But as proposed, outs a fairly cheap and easy option.

 

[elkshadow]

Ten bucks and change. White Labs Alcohol Test Kit Plus