Sparge, Mash Water and Preboil Water calculations - over/under-sparging question

[alagenchev]

I have two extract brews under my belt that turned out fine and I think I want to try AG now. I've been reading a lot on AG before I jump into it and I have some questions and concerns regarding the water calculations.

I'm planning on doing batch sparging and I've seen people recommend anywhere between 1.2-1.3 qts/lb grain for strike water and 1/2 g/lb grain for sparge water. John Palmer on the other hand recommends to keep them about equal. So that's my first confusion. I assume it's because there is different way to skin a cat, but would still be cool to know why the difference in opinion.

My other confusion came from me trying to figure out what are the highest gravity beers I can brew in my boil kettle. Last month I bought an 8 gallon pot from Norther Brewer thinking that I would never make more than 5 gallons worth of beer, so 8 gallons should be plenty. Fast forward a month and now I want to kick myself for not going with ten because I now realize I have to account for evaporation and allow room to prevent boil overs. Regardless, I would like to get as much bang out of my pot as possible before going to my wife and saying I need a bigger one, so I would like to stick with it as much as possible. My thinking was that the more grain I put in, the more water I would need to wash the enzymes off the grain, so I would need a bigger pot to boil more water down to 5 gallons. However, all the treads on this forum are saying that one should do the calculations starting with the pre-boil volume, which is calculated based on target batch size and evaporation rates. Going with this approach, it seems that regardless of grain bill, the water going into the pot will always be the same. That sounds counter intuitive, but nevertheless that's what calculators like this one are using too: http://www.brew365.com/mash_sparge_water_calculator.php
However, this article http://beerandwinejournal.com/pre-boil-volume/ and particularly:

"The benefit of using the second method — collecting a fixed pre-boil volume — is simplicity. For every beer, no matter the size of the grain bill, you collect the same amount of wort and boil for the same amount of time. This makes it easy to plan your brewday.

However, the downside is that the brewer’s extract efficiency decreases with increasing grist weight. For progressively larger grists, more and more sugars are left behind in the grain bed when the brewer stops sparging at his target pre-boil volume. Conversely, for lighter grists, the brewer is likely oversparging — causing the grain bed pH to rise above 5.8 and excess tannins to be extracted." raises the same concerns that I have.

So can someone explain to me how the pre-boil volume is supposed to be the same regardless of grain bill? How is that not affecting efficiency?

If for some reason, I can have constant pre-boil volume regardless of grain bill, does it mean that I can make any beer I want in an 8 gallon pot, provided that I watch for boilovers like a hawk?
Thanks a lot and sorry for the long question.

 

[Yooper]

So can someone explain to me how the pre-boil volume is supposed to be the same regardless of grain bill? How is that not affecting efficiency?

If for some reason, I can have constant pre-boil volume regardless of grain bill, does it mean that I can make any beer I want in an 8 gallon pot, provided that I watch for boilovers like a hawk?
thanks a lot and sorry for the long question.

Except for very small grainbills, which would be oversparged if 7 gallons was drawn off (again, very small grainbills- like 6 pounds of grain!), you can just sparge up to your boil volume.

Yes, you lose some efficiency % in a very large grainbill, but unless you want to boil the wort for 4 hours to boil down the excess volume, it's the easiest and most expedient way to homebrew.

For a 5 gallon batch in my system, I need to start with about 7 gallons of wort due to evaporation. That won't change based on my beer type.

to test your boil off, just put 6 gallons of water exactly in your pot. Bring it to a boil, boil hard for an hour, then cool. Measure the amount of water left- that's your boil off. That will be the same in the same pot on the same burner, regardless of starting volume.

 

[blizz81]

However, the downside is that the brewer’s extract efficiency decreases with increasing grist weight. For progressively larger grists, more and more sugars are left behind in the grain bed when the brewer stops sparging at his target pre-boil volume. Conversely, for lighter grists, the brewer is likely oversparging — causing the grain bed pH to rise above 5.8 and excess tannins to be extracted."

So can someone explain to me how the pre-boil volume is supposed to be the same regardless of grain bill? How is that not affecting efficiency?

The quote above pretty much answers the question below. A lot of people are fine with accepting a relatively-known loss in efficiency as beers get bigger, and will throw more base grains in to accommodate for this. Obviously, you kind of hit a...probably not "exponential" problem here as you get to really big beers. (edit: or you can add sugar or DME/LME)


The other option is to try to maintain your efficiency but extend your boil time. I'm currently using a 10gal boil kettle and even for the barleywine I'm doing tomorrow, that's not quite gonna cut it. In an effort of trying to keep my sparge water volume around my first runnings (strike water minus absorption from the grain) volume, I'm pretty much at 10 gallons of pre-boil volume. How I'm handling it is a three hour boil (where I boil off about 1 gal every 45 minutes), starting with 8gal in the kettle, boiling down to 6gal (first 90 minutes), adding the remaining 2gal, and boiling for another 90 minutes to end up around 6gal:

 

[alagenchev]

Thanks everyone for the responses. This thread helped me worry less about me buying an 8 gallon pot and understand the whole process much better.