[Megary]

I haven't messed with different volumes of strike water for BIAB.  I boil for an hour so I calculate strike volumes based on that, plus my batch size and my system losses.  Pretty simple...a full volume mash.

But...why boil for an hour?

Working backwards in a BIAB (or MIAB) set-up:

1. Longer Boil --> Greater Evaporation
2. Greater Evaporation --> More Strike Water
3. More Strike Water --> Better Grain Rinse
4. Better Grain Rinse --> Better Extraction/Less Grain Needed

#3 above seems like the great unknown (or maybe a leap of faith??) to me, because there has to be some optimal limit to an efficient strike water volume - even if the limit is more practical than theoretical. Or maybe the boil length sets the limit because boiling for longer than xMinutes is detrimental to the finished beer for <fill in the blank> reasons.

This isn't about saving a few pennies on grain but more about the ability to brew bigger beers - without a big corresponding drop in efficiency - in a fixed size kettle.  (I have read that some people "sparge" their BIAB - ie. remove the bag from the kettle and pour water over the top. I have always assumed they did this not to improve efficiency, but rather their kettles simply weren't big enough to full-volume mash.  I mean, if you are going to sparge a BIAB why not just add that sparge water to the kettle to begin with?)

So I wonder if there is an optimal grain rinsing Water/Grist ratio for BIAB.   

[denny]

FWIW, I do BIAB with a 20 min. mash and 20 min. boil.  I do a quick sparge/rinse after the mash.

[Bob357]

There's nothing chiseled in stone that says you need to mash for 60 minutes, or boil for a given period of time. The parameters that are commonly adhered to are outdated, to say the least. Do a little bit of experimenting and find out what puts you in a comfort zone between time, effort and results. There's a bunch of info out there that will give you some insight on the subject.

[BrewBama]

There's nothing chiseled in stone that says you need to mash for 60 minutes, or boil for a given period of time. The parameters that are commonly adhered to are outdated, to say the least. Do a little bit of experimenting and find out what puts you in a comfort zone between time, effort and results. There's a bunch of info out there that will give you some insight on the subject.

+1. That’s what I did. ...but I ended up at 90 min mash


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[Richard]

FWIW, I do BIAB with a 20 min. mash and 20 min. boil.  I do a quick sparge/rinse after the mash.

The Brulosophy people have a "Short and Shoddy" process that involves short mashes and boils like this. It is less efficient, so you have to increase your malt and hops to hit the same targets as a "traditional" recipe. If you value time over money, then that is the way to go. If you are obsessed with squeezing out every last percent of efficiency, then you need to invest more time. Your choice...

[TeeDubb]

I also brew with a BIAB process and incorporate a sparge / rinse step. Part of this is due to my 8 gal mash and boil kettle size, as you note. So I mash and recirculate the wort controlling temperature. I sample the gravity every 10 min or so and find that it tends to settle after 45-60 min. The sparge definitely extracts more sugars and when I combine the first runnings with the second, I have what I need to hit my pre-boil gravity. I have started to incorporate a minimum boil duration and intensity methodology and find it has improved the wort quality (just based on my own judgment). So, I end up between 40 and 75 min boils...whatever it takes to come close to my target post-boil gravity. With the equipment I have now, I incorporate flexibility and I don't worry about historical durations people tend to quote. It does mean that sometimes I adjust my hot-side hop additions on the fly to match what I'm seeing develop for boil duration. The subsequent times I make a recipe I know what to expect.

[Megary]

I'm not married to 60 minute boils, 60 minute mashes or any other historical time parameters...

I'm curious as to an optimal Strike Volume grain rinse (water/grist ratio) with a BIAB mash in the kettle.  If the optimal Strike Volume then tells me I need to boil for 20, 40, 70 minutes or whatever to hit my batch volume...so be it.  Now I'll likely never boil longer than 90 minutes no matter what, but I may boil that long if I can get a measurable, preferable extraction with more mash water.  If its worth it, why wouldn't I?  Its only time and I love brew day!     Again, I'm not concerned about "every last percent of efficiency" but if I can get something worthwhile with less malt then I'm all in.

In other words:
In theory...If a 60 minute mash with x gallons of water and a 60 minute boil gives 1.050 gravity...will a 60 minute mash with x++ gallons of water and a 75 minute boil give an appreciable higher gravity?  Will extra mash water give a better grain rinse?

It's more of a thought exercise and, like Bob said, I won't really know until I experiment, which I probably will on my next batch. 

[denny]

FWIW, I do BIAB with a 20 min. mash and 20 min. boil.  I do a quick sparge/rinse after the mash.

The Brulosophy people have a "Short and Shoddy" process that involves short mashes and boils like this. It is less efficient, so you have to increase your malt and hops to hit the same targets as a "traditional" recipe. If you value time over money, then that is the way to go. If you are obsessed with squeezing out every last percent of efficiency, then you need to invest more time. Your choice...

I was short and shoddy before those guys were born..... . I average 75% efficiency

[Big Monk]

In other words:
In theory...If a 60 minute mash with x gallons of water and a 60 minute boil gives 1.050 gravity...will a 60 minute mash with x++ gallons of water and a 75 minute boil give an appreciable higher gravity?  Will extra mash water give a better grain rinse?

Disregarding any calculations or hard numbers and just focusing on a high level overview, I would expect the following:

1.) Extra strike water would dilute the mash more, meaning that more extract is likely to be in solution, but the overall gravity will likely decrease because of the volume;

2.) The longer boil would mean more boil-off but would likely just be a wash because of the more dilute mash.

Now this doesn't take into account sparging, which could be an equalizer here.

I personally do not sparge. I brew mainly Trappist inspired ales of varying gravity so I maximize first wort extract and let sugars get my OG up.

[Megary]

In other words:
In theory...If a 60 minute mash with x gallons of water and a 60 minute boil gives 1.050 gravity...will a 60 minute mash with x++ gallons of water and a 75 minute boil give an appreciable higher gravity?  Will extra mash water give a better grain rinse?

Disregarding any calculations or hard numbers and just focusing on a high level overview, I would expect the following:

1.) Extra strike water would dilute the mash more, meaning that more extract is likely to be in solution, but the overall gravity will likely decrease because of the volume;

2.) The longer boil would mean more boil-off but would likely just be a wash because of the more dilute mash.

Now this doesn't take into account sparging, which could be an equalizer here.

I personally do not sparge. I brew mainly Trappist inspired ales of varying gravity so I maximize first wort extract and let sugars get my OG up.

Thanks for the reply.  The bold part is my conundrum in a nutshell.  I can't get past the idea that extra strike water would act as some kind of artificial sparge-in-advance.  Maybe it would be a wash as you say, I don't know.  Next brew day I'll commit to a longer boil and the corresponding increase in strike water to see if there is anything worth noting.

I hate when I get hung up on stupid stuff, but its one of the reasons I love this hobby.

[ynotbrusum]

I used to batch sparge with the end result being an even split in volume recovered between the initial strikewater (accounting for absorption and dead space) and the sparge (water in equals water out).  Any more, I simply use most of the water in the strike and sparge with a gallon (5 gallon batch) or two (ten gallon batch).  If I am doing a short mash, I just add extra grain (half pound or so to a 5 gallon batch and a pound or so to a 10 gallon batch) to account for the otherwise lower expected gravity.

But I must say that, anymore, if I am worried too much about ending by a certain time, I just don't brew that day or I start earlier.  Old age gets me to that mindset....

[Big Monk]

In other words:
In theory...If a 60 minute mash with x gallons of water and a 60 minute boil gives 1.050 gravity...will a 60 minute mash with x++ gallons of water and a 75 minute boil give an appreciable higher gravity?  Will extra mash water give a better grain rinse?

1.) Extra strike water would dilute the mash more, meaning that more extract is likely to be in solution, but the overall gravity will likely decrease because of the volume;

The bold part is my conundrum in a nutshell.  I can't get past the idea that extra strike water would act as some kind of artificial sparge-in-advance. 

The big takeaway here is that volume and grain amount are intertwined.

If I have X lbs or kg of grain into Y gal or l of water, I would expect Z gravity. If I then use 2Y gal or l of water, I'd expect something on the order of ~0.5Z* gravity.

More water means more of the extract in the X lbs or kg of grain in solution but it also means less extract because it's diluted.

(*Note: This is not very accurate, i.e. this is "back of the envelope" type stuff.)

[Megary]

In other words:
In theory...If a 60 minute mash with x gallons of water and a 60 minute boil gives 1.050 gravity...will a 60 minute mash with x++ gallons of water and a 75 minute boil give an appreciable higher gravity?  Will extra mash water give a better grain rinse?

1.) Extra strike water would dilute the mash more, meaning that more extract is likely to be in solution, but the overall gravity will likely decrease because of the volume;

The bold part is my conundrum in a nutshell.  I can't get past the idea that extra strike water would act as some kind of artificial sparge-in-advance. 

The big takeaway here is that volume and grain amount are intertwined.

If I have X lbs or kg of grain into Y gal or l of water, I would expect Z gravity. If I then use 2Y gal or l of water, I'd expect something on the order of ~0.5Z* gravity.

More water means more of the extract in the X lbs or kg of grain in solution but it also means less extract because it's diluted.

(*Note: This is not very accurate, i.e. this is "back of the envelope" type stuff.)

Right.  That makes perfect sense and that's exactly why I'm having a hard time with it.   

I'm thinking (dreaming) that the post-boil gravity would be greater than .5Z because the extra water would lead to a more efficient or thorough extraction.  And that somewhere there is an optimal BIAB mash/strike volume that would probably be different for everyone's set-up.  I can't believing that the strike volume makes no difference to extraction at all because I think if taken to the extremes it would be true. Mashing 10# grain in 1 gallon of water vs. 8 gallons vs. 30 gallons.

And it's possible that this dream of mine might not really show up for standard gravity beers.  Maybe this would make more sense for the big boys pushing 1.080 or more??

I apologize for being repetitive.

[Big Monk]

I'm thinking (dreaming) that the post-boil gravity would be greater than .5Z because the extra water would lead to a more efficient or thorough extraction.

There is only a finite amount of extract in X lbs or kg of grain. While it's true that a more dilute mash will have more of the available extract in solution, the dilution, by it's very nature lowers the gravity of the wort.

I see what you are trying to do but you are getting stuck on available extract in solution versus gravity of the solution.

I ran some numbers:

Let's negate losses except for grain absorption. Let's also assume 100% conversion efficiency and assume no-sparge so that we only see first wort extract. I assumed 80% Fine Grind Extract and 4% moisture.

If I mash 5.67 kg (12.50 lbs) of grain into 32 l (8.45 gal) of water, I could reasonably expect ~ 12P (~ 1.048 S.G.) of first wort extract.

If I mash 5.67 kg (12.50 lbs) of grain into 64 l (16.91 gal) of water, I could reasonably expect ~ 6.4P (~ 1.025 S.G.) of first wort extract.

So you can see that the second case is marginally more than the 0.5Z gravity i roughed up before. Either way you shake it, more of the available extract in solution does not translate into an appreciable benefit in gravity, i.e. it is swamped about by the massive drop in gravity of the more dilute mash.

Now granted, that's an extreme case. There is a whole range of more practical increases in volume between Y and 2Y. The real point is that you wouldn't increase volume without a calculated increase in grain amount to offset the change in gravity.

[ynotbrusum]

The Foundry system comes with a recommended table of grain weights and water volumes for its system (both sparging and no sparge - just holds out a gallon for sparging each time, if sparging; but also considers a different boil off rate for 120V vs 240V).  But you have to be accurate in your determination of volume (or you can boil down to the volume necessary to get the gravity at the right number - however, that might throw off the IBU calculated for timing of hop additions, if way off and excessive boiling is needed to hit a target SG).