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

[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