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**KurtB** · 02-17-2012, 07:52 PM

Quote:

Originally Posted by weirdboy

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:

{snip a bunch of math stuff}

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

We have been down the road a number of times. It is becoming also like the secondary vs. extended primary debate...

You assume the vessel is a perfect cylinder with that formula. Unfortunately, my pot has a rounded edge where the sides meet the bottom, a slight flare which makes the top about a 1/2 wider than the bottom, and a dent in the side, all of which renders the "math solution" not very practical. That is why I used the "fill and mark" method, right before I did my first AG batch. I used my boil kettle to heat my strike water so nothing went to waste.

Math may make things simple in a perfect world, but in reality there are enough variables to make the "fill and mark" method just as easy.

That is one of the things that I love about this hobby. There are so many different ways to do the same thing, alll while making good beer.

eobie · 02-17-2012, 08:05 PM

No reason to waste the water. Use the below link to figure out gallons per inch and marka ruler...

http://merrycuss.com/calc/kettle_volume.html

40watt · 02-17-2012, 08:58 PM

Why assume I would waste water? You use your math, and I'll use my eyes.

**eyedoctodd** · 02-17-2012, 09:04 PM

The rounded bottom is no problem to account for with a hybrid of the math and water methods. You can put in known volumes of water at the beginning and mark the stick up to the point where you're over the rounded edge, then use that math calculation to figure it out the rest of the way. Because above the rounded edge, it is a perfect cylinder (unless you're using a sankey keg or other non-cylindrical pot, of course)

**weirdboy** · 02-18-2012, 01:47 AM

Quote:

Originally Posted by KurtB

We have been down the road a number of times. It is becoming also like the secondary vs. extended primary debate...

You assume the vessel is a perfect cylinder with that formula. Unfortunately, my pot has a rounded edge where the sides meet the bottom, a slight flare which makes the top about a 1/2 wider than the bottom, and a dent in the side, all of which renders the "math solution" not very practical. That is why I used the "fill and mark" method, right before I did my first AG batch. I used my boil kettle to heat my strike water so nothing went to waste.

Math may make things simple in a perfect world, but in reality there are enough variables to make the "fill and mark" method just as easy.

A rounded edge bottom is not very difficult to account for, mathematically speaking. Use the volume of the outer cylinder, and then subtract the volume of a quarter of the torus for that curve at the bottom.

Unless the dent is quite large, you aren't really missing a whole lot of volume by assuming it's cylindrical. Certainly within the measurement error of using "known" quantities of water as a substitute. Also unless the diameter is quite large you probably aren't missing too much by just assuming it's a perfect cylinder, either. Again, within measurement error using other methods, I'd wager.

photogscott · 02-18-2012, 09:15 AM

Many professional brewers come from engineering. I see why...

pabloj13 · 02-18-2012, 10:58 AM

Why is everyone so excitable about wasting water? I just notched my dowel as I was pouring in strike water. Two birds, one stone, etc.

**JonM** · 02-18-2012, 12:24 PM

I measure the first runnings in my heat-resistant 1-gallon measuring cup (from William's Brewing). Once I know the volume of the first runnings, I use a known volume for the sparge. Known sparge volume + first runnings volume = total volume.

Not perfect, but it's worked really well so far. One of these days I'll put a sightglass on my kettle.