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How to measure wort in kettle?

How do you guys measure your wort while in the brew kettle to know when you have hit your volume or need to top up, etc? First AG on Sat. looking for pointers.

 happypanties 02-17-2012 05:49 PM

I pre-measured my spoon before brewing my first AG batch. Just add a half gallon of water, mark the spoon with a sharpie, add another half gallon, make another mark, etc... until you get to the top of the pot.

Then when brewing, use the spoon to tell you how much wort you have.

 weirdboy 02-17-2012 05:51 PM

Get yourself a cheapo yardstick from e.g. Home Depot.

Measure the inside diameter of your kettle, in inches. Try to be as accurate as you can on this number.
Calculate the surface area of your vessel. The forumla is:

R = 1/2 * diameter
Pi*R^2

That number also happens to be the number of cubic inches in your kettle, per inch of height.

There are 231 cubic inches in a gallon.

So, the number of inches per gallon (I will call this N) in your kettle is:

N = 231 / (Pi * R^2)

Now, look at the yardstick, and on the back side, mark off with a permanent marker every N inches as a gallon mark. If you want to do half or quarter gallons, that is easy enough...

There is no sense wasting a bunch of water to measure the volume of something that is easy enough to calculate.

 happypanties 02-17-2012 05:52 PM

LOL yes I was thinking of doing it that way too, but didn't want to do all the math :tank:

 Brew-ta-sauraus 02-17-2012 06:01 PM

Quote:
 Originally Posted by happypanties (Post 3797796) I pre-measured my spoon before brewing my first AG batch. Just add a half gallon of water, mark the spoon with a sharpie, add another half gallon, make another mark, etc... until you get to the top of the pot. Then when brewing, use the spoon to tell you how much wort you have.
I did the same as above only in 1 gal increments. Etched my paddle with the marks.

 Brew-ta-sauraus 02-17-2012 06:02 PM

Quote:
 Originally Posted by weirdboy (Post 3797807) Get yourself a cheapo yardstick from e.g. Home Depot. Measure the inside diameter of your kettle, in inches. Try to be as accurate as you can on this number. Calculate the surface area of your vessel. The forumla is: R = 1/2 * diameter Pi*R^2 That number also happens to be the number of cubic inches in your kettle, per inch of height. There are 231 cubic inches in a gallon. So, the number of inches per gallon (I will call this N) in your kettle is: N = 231 / (Pi * R^2) Now, look at the yardstick, and on the back side, mark off with a permanent marker every N inches as a gallon mark. If you want to do half or quarter gallons, that is easy enough... There is no sense wasting a bunch of water to measure the volume of something that is easy enough to calculate.
FYI I didnt waste the water I transferred it to my HLT for the next day brewing. Guess I could have gone the math route as well but I bored and needed to kill some time.

 TheMan 02-17-2012 07:22 PM

I don't really measure mine anymore. After you get your system dialed in you should have almost exact volumes at the end of the boil every time. After my first few boils I measured the amount left and found that I boil off a gallon every half hour. So I start with 7.5 gallons to have my planned 5.5 gallons.

Every once in a while I measure just to see. And every time I have 5.5 gallons give or take 1/4 gallon tops.

 Calichusetts 02-17-2012 07:32 PM

Use a lab thermometer and kill two birds with one stone. Either take measurements from when the thermometer is sitting on the bottom or hanging from the top or both. I can measure my volume to the hundreth of a gallon with ease...not that I need to

 snevey 02-17-2012 07:35 PM

I have a notched aluminum "dowel rod" that I have marked in .5 gallon increments.

 Snafu 02-17-2012 08:25 PM

I use a 4 foot 1 1/4" oak dow rod. I used a wood burning tool to "mark" every 1/2 gal. up to 13 gals.

http://i609.photobucket.com/albums/t...2/IMG_0124.jpg

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