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### Topics - foobrew

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##### Events / NHC BJCP Event Wed Night
« on: April 27, 2011, 03:27:07 PM »
Anyone have any info on this? I've searched everywhere and all I can find is a mention of a "BJCP Judge Reception in the afternoon" on this page:

http://www.ahaconference.org/conference-information/conference-schedule/

I don't see anything on bjcp.org or in the forums there either.

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##### General Homebrew Discussion / Thermal expansion/contraction of wort formula?
« on: November 30, 2010, 04:57:12 PM »
I've been researching this for a few weeks now and have only been able to come with online or in hobby-level homebrew books is anecdotal evidence. I'm trying to find a formula which will output wort volume at a specific temperature based on a known wort volume and temp. For example,

5.0 gallons wort at 68 degrees F = X gallons of wort at 212 degrees F

I've found many references to using .96 or .97 as a factor depending on a wort temp of 212F or 160F, respectively. For example,

5.0 gallons / .96 = 5.2 gallons at boiling

I believe people are basing this factor on the thermal expansion of water formula (Wikipedia: Thermal Expansion):

207 * 10^-6 * (temp in C) * (volume) = expansion volume

So,

207 * 10^-6 * 100 Celsius * 5.0 gallons = 0.10 gallons
0.10 gallons + 5.0 gallons = 5.10 gallons at boiling

Regardless of which one I've used, they both appear to be way off based on my own experience. Over the course of five different brews, I've recorded the following data:

Brew #1
5.25 gal @ boiling, 4.75 gal @ 68F --> 4.75 / 5.25 = .91

Brew #2
5.75 gal @ boiling, 5.25 gal @ 66F --> 5.25 / 5.75 = .91

Brew #3
5.60 gal @ boiling, 5.00 gal @ 76F --> 5.00 / 5.60 = .89

Brew #4
5.65 gal @ boiling, 5.10 gal @ 68F --> 5.10 / 5.65 = .90

Brew #5
5.50 gal @ boiling, 5.00 gal @ 90F --> 5.00 / 5.50 = .91

As you can see, my own measurements show an expansion/contraction rate of about 10% between 68F and boiling which doesn't at all agree with the expansion of water or the .96 (4%) factor thrown around so often. It seems like there must be a thorough formula for wort expansion which has been lab produced but I can't find it. Wouldn't this be covered in one of the professional brewing science texts (which I don't have access to)? Since I'm working on building an online calculator for this, I'd prefer to have a real formula to work with and not just anecdotal evidence. Anyone have any ideas? This would've been a great question for John Palmer I think but I missed out on that one; maybe I should submit it to Rand Moser for the next "Ask the Experts" session?

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