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Give me Sparge Water, or give me...!help

heyo. Did first AG, batch sparged the innkeeper al a Denny Conn method and HD4MARK’s “Goin’ All Grain” on FAQ’s. First off, thanks guys, bout everything went GREAT!! Only prob was post boil volume was about 3.75 gallons instead of 5 gallons.

1.25q per 1lb of grain.= ~<8 gallons mashed in. Sparged w/ enough to bring preboil to 6gallons. Ended up w gravity of 1054 instead of desired 1045, so thinking extraction was spot on.

Q- How do I figure accurate preboil volume to end w/ desired post boil volume?
Thanks to all- brew on!

If you started with six gallons and ended with 3.75, you simply boiled off too much. If it was a 60-miinute boil, you could have lowered the heat to get less boil-off. And if you had stopped the boil at five gallons, you would have ended up at 1.040 (3.75*54/5).

I have a mash water calculator (Mash Water 3.3) on my web site that is simple to use.

http://gnipsel.com/beer/software/beer-software.html

I also calibrate my boil pot before using it for the first time so I can use a tape measure from the top of the pot to the top of the wort and know how many gallons I have in the pot. This way I can be assured that I got my pre-boil volume I wanted.

John

good stuff. thanks for the input. Shadetree, what’s the “54” in that equation?

54 = number of points above SG of water in the case of the wort you’re working with. Since sugar quantity is a constant, and only concentration varies, you just multiply gravity by actual # of gallons, then divide by another volume to see what the gravity would be in that case. For any given wort, the gravity and volume are inversely proportional. In addition, the product of the two numbers should always be the same (in this case, 202.5) as volume and density change (during boiling, for instance). A google search informs me that this number is called total gravity

. A stripped down formula would be v * sg = tg.

Once you know the TG of a wort, you can also find the volume for a specific SG using this formula:
v = tg/sg
In this case (desiring 1.045), 202.5/45 = 4.5 gallons

[edit2]Sorry if that comes off as pedantic, explaining it just helps me to internalize it for myself, and this stuff is still fairly new to me

cheers icky, thanks for the explanation. AS someone previously suggested they do a test boil and measure accordingly to discover evaporation rates for their particular kettle, but since the viscosity/weight related to water is thicker, then wont my evap rates be different than that related to the test boil of water alone?

You’re welcome! My chemistry knowledge is pretty lacking, to say the least, but my guess is that the sugar, salts, etc., will affect how long it takes to start boiling, but not rate of evaporation.

The thicker and more concentrated the “sugar solution” is will make it more difficult to evaporate the same amount of water. The temperature goes up for the boiling point as % sugar increases and heat transfer coefficient is less than for pure water.

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