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Old 10-10-2008, 10:07 PM   #1
Oct 2008
Libertyville, IL
Posts: 333
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I've brewed two moderately-high gravity batches without mashing out, but it's something that I think I'd like to master, especially for when I do lighter beers.

So, thinking this through in my head...

In order to bring my ~150-155 degree mash up to 170 degrees, I'm going to need a good dose of really hot water.

Q#1) How's about 2 gallons of boiling water for a place to start? It seems reasonable to think that the size of the mash plays a factor. Is there a formula or guide?

Q#2) When I add this water to the mash, I presume I'm going to have an excess of water above the grain level. Is it then appropriate to slowly drain out wort into the kettle to the point where my water is an inch above the grain and then commence w/fly-sparging as usual?

(I realize I'm probably not the first to ask this, but there are so many threads with very general titles to search through... so, sorry mods.)

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Old 10-10-2008, 10:14 PM   #2
scinerd3000's Avatar
Mar 2008
Milton, De
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Green Bay Rackers--Mash Calculators - Batch Sparge Calculator

google is your freind
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Old 10-11-2008, 12:24 AM   #3
Oct 2008
Libertyville, IL
Posts: 333
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Originally Posted by scinerd3000 View Post
Well, I'm certainly not a packer's fan, but it'll do. And Google isn't the best conversationalist I've ever met. I prefer people.


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Old 10-11-2008, 02:05 AM   #4
WBC's Avatar
Jun 2007
La Puente, CA, California
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When you mash out use a calculator to figure quantity of the boiling water addition. Add in small batches while stirring.

If your mashtun is almost full:
You can also heat some of the mash liquid only to a boil (decoction mashout) and pour that back into the mash while stirring. This should be added in several additions so you can sneak up to the mashout temperature without going over temperature. Remember when calculating that you have removed a given quantity from the mashtun that needs to be in the math when figuring your decoction/mashout. Beersmith will do this automatically.

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Old 10-11-2008, 02:20 AM   #5
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Oct 2005
Long Island
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It's going to depend on the size of the batch, the amount of water, the amount of grain in the mash, and possibly on the thermal mass of the mash tun.
For 5g batches in a 5g cooler mash tun, I use up to 1g boiling water (mashing at 1 qt / lb). For brews with an OG of about 1.075, I would exceed the capacity of the cooler before reaching the required temperature. For brews with an OG less that 1.060, I don't need the full gallon. However, with the 10g cooler (which I've only used twice with a mash out), I need much more water as the larger cooler sucks a lot more heat out of the addition. The first time, I used my normal amount of water, and didn't get up to 155. The second time, I used more, and got it up to about 160. In the second instance, I used much more water than the Promash calculater recommended. I suspect that Promash may be more accurate if I plugged in a value for the thermal mass of the MLT. What I am saying, is that the volume of water really depends on the amount of grain, the amount of water, and your equipment.
With the 5g MLT, I boil more water than necessary, and add some, stir well, and measure the temperature. (Stirring well is very important). If the temperature is not high enough, I add more water and repeat.
I don't know what I'm going to do with the 10g MLT, other than experiment to find what works.


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Old 10-11-2008, 03:07 PM   #6
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May 2007
Nashua, NH
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There are several brewing software packages out there that can do this kind of calculation for you easily and accurately, such as Beersmith or beer tools pro.

Not trying to say you shouldn't ask questions by any means, but brewing software can save you a ton of time on a regular basis - I consider it an absolutely essential tool.

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Old 10-11-2008, 03:27 PM   #7
Sep 2008
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I like decoction mash outs, I think it's 40% thin mash...I've also used Charlie Ps formula before and it works well IIRC it's half the amount of mash water @ boiling so if your strike was 3 gallons to reach 152F then mash out would be 1.5 gallons.
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