Monitor SG as beer is fermenting

Has anyone ever used a scale to get SG’s of beer while it’s fermenting?
This is what I was thinking about. You could get a weight of the empty carboy and take the SG before you add the beer to the carboy.
So lets say the carboy is 5 lbs and the beer is 1.050. Now you just put your carboy on the scale and take a quick weight.
So say it weights 50.9 lbs, you know your is beer 1.050 SG and the carboy weights 5 lbs so you have 45.9 lbs of beer.
To convert SG to pounds per gal is 1.050 * 8.34(the weight of water)= 8.75 ppg so know you know the weight in ppg of your beer. Take the weight of Total beer in the carboy divided by weight in ppg. 45.9/8.75= 5.24 gal of beer.
So when you think your beer is done just turn on the scale and take a weight. So you get 49.1 then -5 lbs for the carboy. 44.1/5.24=8.42 ppb /8.34= 1.009 SG
Not really much work involved really to get SG’s as the beer ferments

10 points for creativity, but you've got a lot more than just beer in there impacting your scale's reading. Even assuming you have zero break or hop mass in there, you've still got to account for the yeast. Unless you can figure out a way to accurately estimate yeast mass, weight won't do it for you.

Yes very true. You could account for the break and hop mass slightly after you do it the 1st time. Just weigh is when your all done and just get some idea what you have left. But its more of just a rough SG and get a ballpark of how fermentation is progressing.

dmcoates said:

Yes very true. You could account for the break and hop mass slightly after you do it the 1st time. Just weigh is when your all done and just get some idea what you have left. But its more of just a rough SG and get a ballpark of how fermentation is progressing.

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The difference between the density of an OG and an FG is on the order of 3%. There's really no practical way to accurately place yourself in that small of a margin, even for a ballpark guess. The unpredictability of yeast mass (not to mention evaporation, etc.) would throw your reading off too much. It would be like trying to predict the temperature in your oven by holding a thermometer in your living room.

I think I might agree with the issue of yeast mass, any break or hop material is a constant right? However, if I can neither create nor destroy matter than wouldn't any yeast multiplication be using nutrients available (not changing gross weight)? The vast majority of weight loss could be contributed to the production of alcohol by the yeast?

Just throwing a couple ideas out there.....

step said:

I think I might agree with the issue of yeast mass, any break or hop material is a constant right? However, if I can neither create nor destroy matter than wouldn't any yeast multiplication be using nutrients available (not changing gross weight)? The vast majority of weight loss could be contributed to the production of alcohol by the yeast?

Just throwing a couple ideas out there.....

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Sorta. The fact that yeast multiplication doesn't change gross weight is actually the problem. Some of your consumed sugar is being vented as CO2, some is turning into yeast mass. Unless you can know how much of each is happening, you can't make an even vaguely accurate measurement.

MalFet said:

Sorta. The fact that yeast multiplication doesn't change gross weight is actually the problem. Some of your consumed sugar is being vented as CO2, some is turning into yeast mass. Unless you can know how much of each is happening, you can't make an even vaguely accurate measurement.

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10-4

Wasn't really thinking that while multiplying your are not producing alcohol, just simple changing one thing to another with some possible release of gasses and maybe some heat produced...

I do still think there is something to be said for very close monitoring and correlation with OG and exact pitch rate (knowing viabilty and vitality)... hmmmmm......

step said:

I do still think there is something to be said for very close monitoring and correlation with OG and exact pitch rate (knowing viabilty and vitality)... hmmmmm......

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If you find an accurate way to model yeast population dynamics, please post it here first! I'd love to replace my hemocytometer with a simple equation.

MalFet said:

If you find an accurate way to model yeast population dynamics, please post it here first! I'd love to replace my hemocytometer with a simple equation.

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I think the hemocytometer would be the most important part. Initial cell counts with OG and Strain and detailed weights correlated with SG and you might have something. But you would always need those darn cell counts...

...and temperature, and wort composition, and hop quantities...

Many a person has tried to model yeast populations, but none of the results have been terribly good. It's a complex system, to use the jargon. If you find a way to model it simply, that will be the bigger achievement, not finding a way to estimate gravity based on weight.

MalFet said:

...and temperature, and wort composition, and hop quantities...

Many a person has tried to model yeast populations, but none of the results have been terribly good. It's a complex system, to use the jargon. If you find a way to model it simply, that will be the bigger achievement, not finding a way to estimate gravity based on weight.

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I'm not saying it can be done at all and certainly not simply. I think temp is a given and BU:GU but wort composition is even complicated by mash schedule... man what a chase your tail endeavor!!! Like trying to model our current climate changes huh? I really do appreciate your responses though