Author Topic: Measuring a Gallon  (Read 1516 times)

Offline flbrewer

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Measuring a Gallon
« on: December 12, 2014, 01:07:47 AM »
I realized recently that my bottling bucket is off by 1/2 gallon (based on the markings compared to Pyrex measuring cups). THEN I started to wonder, well what if my Pyrex is off? Someone mentioned that you should measure a gallon by weight to verify. Any thoughts?

Offline Stevie

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Re: Measuring a Gallon
« Reply #1 on: December 12, 2014, 01:19:02 AM »
I'd put my faith in the Pyrex before a bottling bucket. A gallon of water at 60° is about 8.35 lbs.

I find the best way to calibrate is to first calibrate a half gallon in some sort of container. Then use that half gallon to calibrate larger containers. Less counting = less chances for a mistake. "Was that 12 or 13."

Offline 69franx

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Re: Measuring a Gallon
« Reply #2 on: December 12, 2014, 01:39:11 AM »
This is something I know I need to do.
Frank L.
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Offline HoosierBrew

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Re: Measuring a Gallon
« Reply #3 on: December 12, 2014, 01:46:41 AM »
+1.  And if you calibrate your kettle (via wooden dowel or whatever) you know exactly how much is going into the bucket before then. Gotta have accurate volumes to get accurate efficiency.
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Offline IPAnic

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Re: Measuring a Gallon
« Reply #4 on: December 12, 2014, 02:02:49 AM »
I've used a 1-gallon water jug to incrementally mark all my vessels. It's not an absolute scientific measure, but it's been more than accurate enough for me for 25+ yrs. Plus, the marks allow me to focus my OCD toward the next big problem I have no control over:) Good luck.

Offline flbrewer

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Re: Measuring a Gallon
« Reply #5 on: December 12, 2014, 02:04:46 AM »
Yeah, I think this has caused some carbonation issues in the past with me. Damn you bottling bucket.

Offline pete b

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Re: Measuring a Gallon
« Reply #6 on: December 12, 2014, 03:13:27 AM »
I'm always thinking 1 gal water = 8 pounds. What exactly are the quantifications about that?
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Offline Stevie

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Measuring a Gallon
« Reply #7 on: December 12, 2014, 03:33:11 AM »
I'm always thinking 1 gal water = 8 pounds. What exactly are the quantifications about that?
Close enough for math in the head. In my opinion.

A liter weighs 1 kilogram. There are 3.78 liters in a gallon. A gallon weighs 3.78 kilos or 8.33 pounds.

I was wrong about the 8.35. That's at 32°, not 60°. And here I thought I would never use this conceptual science or math in life.
« Last Edit: December 12, 2014, 03:40:18 AM by Steve in TX »

Offline aokeovn

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Re: Measuring a Gallon
« Reply #8 on: December 12, 2014, 03:49:32 AM »
But I think It's useful for us in the life.  :) housse iphone 6 plus coque iphone 6 plus
« Last Edit: December 18, 2014, 02:25:28 AM by aokeovn »

S. cerevisiae

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Re: Measuring a Gallon
« Reply #9 on: December 12, 2014, 03:53:46 PM »
A U.S. gallon of water displaces 231 cubic inches (Queen Anne's Gallon).   If you can find a perfectly or near perfectly cylindrical vessel (e.g., a kettle), you can calculate volume in gallons and fractions of a gallon using the following formula:

volume_of_cylinder_in_gallons = 3.14 x radius x radius x height_of_the_liquid_column / 231

Example:

My Vollrath 6-gallon Tri-Ply kettle is 12" wide (diameter) x 12.5" high (height).  Radius is half the diameter; hence, the radius of this kettle is 6".  I usually boil down to approximately (~) 8" of liquid in this kettle.   The volume of a liquid increases roughly 5% at 100C (212F).   What is the volume of wort + break + hops in the kettle?

volume_at_100C = 3.14 x 6 x 6 x 8 / 231  = ~3.92 gallons

volume_at_room_temperature = 3.92 x 0.95 = ~3.72 gallons

The formula shown above will not work with a bucket because it is actually a modified cone.  This type of geometric shape is known as a conical frustum. 

volume_of_a_conical_frustrum_in_gallons = 3.14 x height x (radius_1 + radius_2 + (radius_1 * radius_2)) / 3 / 231 

Where radius_1 = internal diameter (width) of the bucket at the bottom / 2, and radius_2 = internal diameter of the bucket at the top of the liquid column / 2
« Last Edit: December 13, 2014, 12:50:07 AM by S. cerevisiae »

Offline joe_feist

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Re: Measuring a Gallon
« Reply #10 on: December 12, 2014, 05:10:24 PM »
Love the math. I don't have the dimensions of my kettle with me, but my brew kettle is 1" = 1 gallon. Had to smile when I saw that. Was it designed that way or am I just lucky? I don't know, but it seems to work out for me.
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Offline Stevie

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Re: Measuring a Gallon
« Reply #11 on: December 12, 2014, 05:27:41 PM »
Alcohol obviously weighs less as well. I think it's about 79% of  water. So if weighing after fermentation, the amount will be different.

Offline morticaixavier

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Re: Measuring a Gallon
« Reply #12 on: December 12, 2014, 05:40:32 PM »
Alcohol obviously weighs less as well. I think it's about 79% of  water. So if weighing after fermentation, the amount will be different.

not only does it weigh less than water, it infiltrates between the water molecules and can effectively occupy the same space as the water.

https://www.youtube.com/watch?v=84k206qaVRU as explained by one of Bill Nye's helpers.
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S. cerevisiae

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Re: Measuring a Gallon
« Reply #13 on: December 13, 2014, 01:52:55 PM »
Love the math. I don't have the dimensions of my kettle with me, but my brew kettle is 1" = 1 gallon. Had to smile when I saw that. Was it designed that way or am I just lucky? I don't know, but it seems to work out for me.

Is the internal width of your kettle 17"?   

Offline narcout

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Re: Measuring a Gallon
« Reply #14 on: December 13, 2014, 05:20:02 PM »
I realized recently that my bottling bucket is off by 1/2 gallon (based on the markings compared to Pyrex measuring cups). THEN I started to wonder, well what if my Pyrex is off? Someone mentioned that you should measure a gallon by weight to verify. Any thoughts?

My bet is that your Pyrex measuring cup is accurate and your bottling bucket is not.  You could always check your Pyrex against another measuring cup to verify.  That would be less of a hassle than measuring by weight. 
It's too close to home
And it's too near the bone