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-   -   calculating boil off? (http://www.homebrewtalk.com/f36/calculating-boil-off-201434/)

maida7 10-19-2010 03:10 PM

calculating boil off?
 
I've recently changed my brewing set up. New larger pot and mash ton so I can do 10 gallon batches. As a result I need to get a handle on my new boil off rate for the big pot.

Would it be accurate to do a test boil with water? Like fill the pot with 14 gallons of water and then boil that for 60 min. Cool it and take a post boil reading. Is this accurate or am I missing something?

Naked_Eskimo 10-19-2010 03:22 PM

Until you actually do a bunch of brews and can accurately do the measurements with a "real" brew, doing the water boil-off is a good way to get an estimate.

wilserbrewer 10-19-2010 03:24 PM

Sure that would work, boiloff varies tremendously w/ ambient temperatures and wind, kettle dimensions and heat applied. Basicly it is just trial and error. Rather than go through the excersize of boling water, I would just make a batch and collect what I felt was a little extra runnings. Simply extend the boil if needed, or add a touch of water if short.

Ohio-Ed 10-19-2010 04:43 PM

You can do a test boil to get an idea of what your boil off will be. But you cannot use that as a percentage to calculate the loss for other size boils. If all other conditions are the same, your volume loss will be similar (not identical) regardless of the size of your boil.

As wilserbrewer said... best bet is to make beer and learn how your system reacts.
Personally, I would prefer to undershoot the volume and slowly add water in the last 15 minutes than to overshoot. If you extend the boil time to reduce the volume, it will impact your hop utilization. Of course adding water to the end of the boil tends to kill the boil, so starting with the correct volume is preferred.

Ed

kanzimonson 10-19-2010 06:50 PM

I concur that a test boil won't give you that much information. Your propane regulator's output changes with the slightest turns... I basically have to figure out how high my regulator should be every single brew, by watching the boil and listening to the fire. Even still, I measure the volume during the boil at least a couple times to make sure I'm on target.


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