SG and weight - Home Brew Forums

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04-21-2012, 12:14 AM   #1
oakbarn

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Jun 2011
Argyle, Texas
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Do I have this correct

A wort with an SG of 1.052 would weigh 8.77894 pounds

I am trying to figure Volume by weight as I can get a heavy duty scale for \$44 off Amazon. Good flow meters are much more and have greater problems with accuracy.

04-21-2012, 12:59 AM   #2
Hex23
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Jun 2010
Illinois, Lake County
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I assume you mean 8.77894 pounds per gallon? The density would depend on temperature, but that's pretty close. Are you trying to measure the CO2 loss to measure the fermentation progress? Or just measure volume indirectly. What are you looking to do?

04-21-2012, 11:48 AM   #3
ajdelange
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Aug 2010
McLean/Ogden, Virginia/Quebec
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Apparent specific gravity is the weight determined in air of a volume of wort at a specified temperature divided by the weight, also determined in air, of an equal volume of water at a specified, but not necessarily the same, temperature. Thus one can determine the apparent weight of a volume of wort by multiplying the apparent weight of an equal volume of water by the apparent specific gravity.

04-21-2012, 11:56 AM   #4
ACbrewer
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Jan 2011
Fredericksburg, VA
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I don't see how you got to 8.77894 pounds with a OG of 1.052 I mean 1 Gallon is 8lb, so 8*1.052=8.48, not 8.77894

04-21-2012, 12:11 PM   #5
ajdelange
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McLean/Ogden, Virginia/Quebec
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A gallon of water weighs (in vacuo) 3.78541178(liters/gal)*998.203(grams/liter) / 453.59237(grams/pound) = 8.33041 pounds per gallon at 20 °C. Thus a gallon of wort at 1.052 (20 °C/20 °C) weighs approximately 8.76359 (with the approximate being because 8.33041 is the true (in vacuo) weight of a gallon of water (not adjusted for air weighing).

04-21-2012, 01:47 PM   #6
oakbarn

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Jun 2011
Argyle, Texas
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I am trying to measure volume in my MLT (just water) and Wort in the Fermenter. I based the calculation on 1 gal of water = 8.345 pounds at 68 degree. I got that figure off the internet. I just wanted to know if the math was correct. If it is, I plan to purchase two scales.

I would put one under my MLT and the other under my fermenter.

I would add 20 gallons of distilled water at 68 degrees and get the exact weight of that water on both scales. That would be my base line for each scale. I would likely check the at 5, 10, and 15 gal to see if the scales were accurate linier,

I would calibrate my Hydrometers at with that water as well.

I guess it would also be a good idea to check the weight in the MLT at 150 degrees as well although I am sure I could calculate that delta if I can find the denisty temp factor.

I am just trying to decide on a 440 pound scale or a smaller one. I do not want to even get need the top of the range and was trying to figure what the max poundage I would have in my MLT and in My fermenter.

MLT Total = MLT # + WaterVol# + Grain#

Ferementer Total = Fermenter# + WortVolume#

I was a pilot and we never though about gallons of fuel. The fuel was pounds. Now volume in gallons (how we purchased) the fuel did equate to pounds (and it did vary by temp). That got me to thinking I could measure volume by weight.

The chemist in me wants to play mad scientist.

04-21-2012, 04:25 PM   #7
ajdelange
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McLean/Ogden, Virginia/Quebec
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Quote:
 Originally Posted by oakbarn I was a pilot and we never though about gallons of fuel.
Someone else must have been paying for it. I knew 6lbs/gal (SG ~ 0.75) but was also very aware that it was \$0.50 per gal. I remember how appalled we all were when the price topped \$1.00 and I remember the first time it cost me over \$100 to put 64 gal of avgas in my plane. I now pay that much to fill my car.

04-21-2012, 04:48 PM   #8
mabrungard

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Feb 2011
Carmel, IN
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If I recall, AJ's brewery uses scales on the fermenter or kettle to measure volume. He would be well versed in the subject!
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04-21-2012, 05:27 PM   #9
SPLASTiK
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I'm one of those strange people who weigh water and wort with scales too... except I use metric and pretend 1L is always 1kg regardless of temperature. So a liter would be 1052 grams, makes for slightly easier math.
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04-22-2012, 12:07 PM   #10
ajdelange
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Quote:
 Originally Posted by mabrungard If I recall, AJ's brewery uses scales on the fermenter or kettle to measure volume. He would be well versed in the subject!
I do indeed have load cells under the stand upon which my mash tun/kettle sits. This does make some things easier. A pound of water is a pound of water at whatever temperature, 100 pounds of 12 °P wort contains 12 pounds of extract etc. OTOH if the dimensions of your vessel are regular it's an easy matter to determine how much volume change an inch change in depth corresponds to under hot and cold conditions. A tape measure is less expensive than load cells!