A way to find alcohol percentage without even opening the fermenter!

[dantodd]

If you are going to go through all that trouble, wouldn't it be easier to just capture and measure the CO2 created?

 

[mew]

You are right, but the other issue is what range is your scale and how accurate do you want it to be? The further away you get the scale from the fulcrum, the more exaggerated the forces on it will be.

I was going to use a balance system with weights and no scale. I would use some large weights and some 1/2 gram increments. I could make the other lever arm the longer one, but then I'd need about 100 lbs of weight to balance the out the carboy.

 

[Sir Humpsalot]

I was going to use a balance system with weights and no scale. I would use some large weights and some 1/2 gram increments. I could make the other lever arm the longer one, but then I'd need about 100 lbs of weight to balance the out the carboy.

Nothing wrong with that set up, but don't forget to include a bubble level or something to tell you when it's balanced out...

 

[Sir Humpsalot]

Wait a second though... I think that 2.5lbs figure is wrong.

* 1 gallon of water equals 8.33 lbs.
* 1 gallon of gasoline equals 5.8 to 6.5 lbs.
* 1 gallon of ethanol equals 6.59 lbs.

So... each gallon of alcohol is 1.74lbs lighter. So if we want a system that measures up to 10% ABV, then 10% alcohol, 90% water equals .174lbs of difference. Five gallons of 10% alcohol equals .87lbs.

5 gallons @ 5% ABV equals .435lbs of changed mass.

what am I not understanding?

 

[Orfy]

You've lost me.

If it's a design exercise then fine but if you're thinking of doing it then I really am at a loss as to what is wrong with this method?

 

[Sir Humpsalot]

You've lost me.

If it's a design exercise then fine but if you're thinking of doing it then I really am at a loss as to what is wrong with this method?

Picture this: You have a one-foot tall scale hanging from your ceiling, connected to a balancing beam. Instead of telling you how many pounds are on the scale, it's marked off in ABV- 0%....1%....2%....3%....4%....5%....6%....7%....8%....9%....10%....11%....12%

You set the carboy on the balancing beam, add the necessary amount of counterweight and fidget it around until you've got the scale zeroed out. You then look at the little red indicator on the scale and it says this:

0%....1%....2%....3%....4%....5%....6%....7%....8%....9%....10%....11%....12%
^

Every few days or few hours, or whenever the mood strikes, you walk over and look at the scale. Maybe after a few hours, you walk over and look again and it says:
0%....1%....2%....3%....4%....5%....6%....7%....8%....9%....10%....11%....12%
........^

Then a little later, you check it out:
0%....1%....2%....3%....4%....5%....6%....7%....8%....9%....10%....11%....12%
............................^

Then after a few days you look and you've got:
0%....1%....2%....3%....4%....5%....6%....7%....8%....9%....10%....11%....12%
........................................................^


So you uncap the carboy, take the S.G. just to confirm your reading before racking off to secodary or whatever.

Is it useful? Marginally so, since you can easily recognize a stuck fermentation without continually opening and closing your fermenter to take a reading. More importantly, for folks who have a dedicated brewing space, it's a very easy way to show people what you are doing and how it works. Explain to a total newb how a hydrometer works and what the numbers mean and their eyes will glass over. Point to a little arrow on a scale that says 6.2%ABV and then they will GET IT instantly.

Is it appropriate for someone like me who will be shuttling carboys and brewkettles around his tiny living space? Not really. But if you've got the dedicated space, and if you pride yourself on showing off what you are doing when brewing beer, then this is a very cool gadget (assuming it works). Necessary? Certainly Not. Cool, Easy to explain, Fun to watch, and likely to reduce the risk of infection in your brews? I would say so.

 

[Orfy]

I'll have one!

 

[Sir Humpsalot]

I'll have one!

See? I knew you'd come around!

The only difference between what I'm talking about above and what everyone else is talking about is the way you set up the scale (whether it's over or under the carboy or the weights or whatever), and a little piece of paper that you would presumably create yourself with a sharpie, a piece of paper, and some scissors which you could tape over the scale to make it read %ABV instead of pounds.


In other words, there is the potential for it to be a very cool set up if the concept is proven to be sound and workable. Obviously factors such as the amount of liquid in the air lock, the weight of a blow off tube, or lost krausen from an over-active fermentation could screw this up. But, if it works... then there's potential there for further development into something like I described.

 

[Kaiser]

what am I not understanding?

I'm not sure if you are approaching this corectly. The fermentation of 20L wort with 12*P (1.048) and 65% fermentability could be aproximated as this:

20L water + 2.51kg extract -> 20L water + 0.81 kg ethanol + 0.81 kg CO2 + 0.87 unfermentable extract

note that is is an aproximation that doen't account for the yeast that is created. The CO2 is driven off and the weight difference will be 0.81 kg (~1.8lb).

Kai

 

[Sir Humpsalot]

I'm not sure if you are approaching this corectly. The fermentation of 20L wort with 12*P (1.048) and 65% fermentability could be aproximated as this:

20L water + 2.51kg extract -> 20L water + 0.81 kg ethanol + 0.81 kg CO2 + 0.87 unfermentable extract

note that is is an aproximation that doen't account for the yeast that is created. The CO2 is driven off and the weight difference will be 0.81 kg (~1.8lb).

Kai

I'm gonna have to brush up on my chemistry. I'm more of a physics guy....

 

[MattD]

I'm not sure that the whole yeast issue really is an issue. Mass must be conserved, it doesn't come from nowhere. Those yeasties that are growing in your carboy are MADE OF wort. The yeast ate the wort, turned it into little yeast pieces, and reproduced. So overall, I'm not sure there would be a weight change there. Correct me if I'm missing something.

My issue with this is, how are you going to account for all the CO2 that's still in solution in the wort? All that is produced will not have blown off, so your calculation would always be low. I'm not sure how you could calibrate this error away, as there's no way to know how much gas is still dissolved in the solution without taking temperature and pressure measurements inside the carboy.

 

[Sir Humpsalot]

Matt- there is only atmospheric pressure in a primary fermenter. We're talking about the primary here. Sure there will be small amounts of gas in the wort, but since the primary is open to the atmosphere (via the airlock), the level of gas ought to be pretty constant.

 

[dantodd]

I'm not sure that the whole yeast issue really is an issue. Mass must be conserved, it doesn't come from nowhere. Those yeasties that are growing in your carboy are MADE OF wort. The yeast ate the wort, turned it into little yeast pieces, and reproduced. So overall, I'm not sure there would be a weight change there. Correct me if I'm missing something.

The alc% is a ratio of alcohol to liquid. Anything that adds volume which is not liquid or alcohol must be taken into account. The hops mass can be easily be accounted for because you know what the volume added was. However; the multiplication of the yeast converts mass in the liquid into solid. Cold and hot break, likewise, convert liquid into solid. Since we cannot assume that the break material and dead yeast cells have the same abv% of the beer it must be accounted for to get an accurate measurement.

 

[dibby33]

This idea is good. The level of insantity to both come up with this idea and to follow it through impresses me

Looking forward to seeing the pictures and the Proof Of Concept

 

[mew]

Once the bugs are worked out, I think it'll be an accurate and easy method.

 

[dibby33]

my $0.02 : Would atmospheric pressure have an effect?

 

[dantodd]

Once the bugs are worked out, I think it'll be an accurate and easy method.

I'm quite certain it won't but it is fun to discuss.

 

[knipknup]

My personal favorite method of measuring ABV is drinking a bottle on an empty stomache, but I digress...

 

[Kaiser]

Why bother with setting up a scale. Just get one of these http://www.sensotech.com/download/LSM033_01.pdf
and stick it down the carboy opening

They even come with a nice and colorful display. Man, I wish that stuff would come at a price affordable for the home brewer.

Interesting to read that they use the sonic speed in the solution to determine the extract content (gravity).

Kai

 

[Pimp Juice]

I use to work with this russian that made his own moonshine(vodka) and wine when he lived out there. Booze was illegal so they had to make it. I was talking about airlocks and he didn't have a clue what I was talking about.

They would tie a latex glove on to the end of the carboy, that may be a good way to gage the amount of co2 released.

 

[rdbeer]

I'm not sure if you are approaching this corectly. The fermentation of 20L wort with 12*P (1.048) and 65% fermentability could be aproximated as this:

20L water + 2.51kg extract -> 20L water + 0.81 kg ethanol + 0.81 kg CO2 + 0.87 unfermentable extract

note that is is an aproximation that doen't account for the yeast that is created. The CO2 is driven off and the weight difference will be 0.81 kg (~1.8lb).

Kai

I just bought this scale on ebay: item#200059710501

It's a 55lb scale with 0.5 oz precision. If the weighing method works, it should give better than 2% accuracy for the Kaiser's example above.

Not nearly as cool as a giant balance, but at $23 shipped, worth a try.

mmh... on second thought, not sure how stable it is over time. But in any case, worst error according to a review was 2.5 oz, which would be about 9% error in abw, still not terrible.

Hopefully, readout will be in approx. oz of alcohol per batch, if the scale can handle a 40+ pound tare weight.

Dirk