Author Topic: Stout fermentation question  (Read 1256 times)

Offline BrewBama

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Stout fermentation question
« Reply #30 on: January 18, 2021, 10:29:41 PM »
The paper inside the tube that has the SG scale on it can come loose. if it slides around, it could give different readings.

Ya know, that's what I've always heard, but in 23 years of brewing with hydrometer I've never had it happen.  Have any of you had personal experience with this?

YES.  I have been using the same hydrometer since 1999, never broke it.  Calibrating in plain water, it has in fact changed several times over the years, a point up or down here & there every few years.
In the Army when we would weigh and balance an acft we would fill the fuel tanks and take a hydrometer reading. But before we logged the hydrometer reading we would have to perform a correction factor based on barometric pressure. Once we had the corrected hydrometer reading we could properly determine fuel density.

Could it be your deviations were due to barometric pressure differences?

There are many environmental factors that affect the accuracy of the hydrometers reading. Room temperature, liquid temperature and air pressure are the main factors to correct and account for in taking accurate measurements with a hydrometer.

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« Last Edit: January 18, 2021, 10:46:18 PM by BrewBama »
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Offline dmtaylor

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Re: Stout fermentation question
« Reply #31 on: January 18, 2021, 11:02:30 PM »
In the Army when we would weigh and balance an acft we would fill the fuel tanks and take a hydrometer reading. But before we logged the hydrometer reading we would have to perform a correction factor based on barometric pressure. Once we had the corrected hydrometer reading we could properly determine fuel density.

Could it be your deviations were due to barometric pressure differences?

Liquid water is, for most intents and purposes, incompressible at normal barometric pressures.  Pressure would have to change in a huge way, like climbing a mountain (significantly reduced pressure) or increased by ~20 atmospheres (like trying to land on Jupiter) just to change the specific gravity by 0.001.

In other words, no, that ain't it.
Dave

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Offline BrewBama

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Stout fermentation question
« Reply #32 on: January 18, 2021, 11:56:33 PM »
It’s not the liquid’s density that is of concern. It’s the air’s density. All the electronic density devices have a barometric pressure sensor built in to counter any differential. Granted, the change would be small but can affect the reading. It is also accounted for during calibration of hydrometers:




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« Last Edit: January 19, 2021, 12:02:26 AM by BrewBama »
“From man’s sweat and God’s love, beer came into the world.” — St. Arnold

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Offline RC

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Re: Stout fermentation question
« Reply #33 on: January 19, 2021, 12:14:22 AM »
It’s not the liquid’s density that is of concern. It’s the air’s density. All the electronic density devices have a barometric pressure sensor built in to counter any differential. Granted, the change would be small but can affect the reading. It is also accounted for during calibration of hydrometers:




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I had to think about this one. It's because there is air of fixed pressure inside the hydrometer, which makes its flotation partially a function of barometric pressure, which makes sense...is that correct?

Offline BrewBama

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Stout fermentation question
« Reply #34 on: January 19, 2021, 12:54:11 AM »
I have a rudimentary understanding. I just recalled having to call the tower to get the barometric pressure to weight acft and apply that to factor out any difference from a standard day at MSL.

Knowing the Army operates all over the world yet only has one standard for weighing an acft, it may simply be accounting for acft in say, Savannah, to those in say, Colorado, like Dave said.
« Last Edit: January 19, 2021, 01:45:33 AM by BrewBama »
“From man’s sweat and God’s love, beer came into the world.” — St. Arnold

Brewed in the Tennessee Valley. Rocket City — Huntsville AL

Offline neuse

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Re: Stout fermentation question
« Reply #35 on: January 21, 2021, 03:38:58 PM »
The paper inside the tube that has the SG scale on it can come loose. if it slides around, it could give different readings.

Ya know, that's what I've always heard, but in 23 years of brewing with hydrometer I've never had it happen.  Have any of you had personal experience with this?

YES.  I have been using the same hydrometer since 1999, never broke it.  Calibrating in plain water, it has in fact changed several times over the years, a point up or down here & there every few years.
In the Army when we would weigh and balance an acft we would fill the fuel tanks and take a hydrometer reading. But before we logged the hydrometer reading we would have to perform a correction factor based on barometric pressure. Once we had the corrected hydrometer reading we could properly determine fuel density.

Could it be your deviations were due to barometric pressure differences?

There are many environmental factors that affect the accuracy of the hydrometers reading. Room temperature, liquid temperature and air pressure are the main factors to correct and account for in taking accurate measurements with a hydrometer.

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BrewBama - It seems like this might be a negligible affect in a normal environment. Do you remember how much difference you saw with air pressure changes in the normal range?

Offline BrewBama

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Re: Stout fermentation question
« Reply #36 on: January 21, 2021, 04:50:04 PM »
No. It was many moons ago. I imagine it was a very small difference.


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“From man’s sweat and God’s love, beer came into the world.” — St. Arnold

Brewed in the Tennessee Valley. Rocket City — Huntsville AL