Imp. Stout Efficiency and Boil Time

[Rob2010SS]

Getting ready to brew an imperial stout in a couple of weeks here. Still learning a bit about impy's from the last few I've done.

I know to plan on a crazy low lauter efficiency here. I'm planning for 65%. I also know that on my past impy's, even with a 90-120 min mash and planning for the lower efficiency, I've still missed the mark on OG by a little bit. One thing I have NOT ended up doing in the past is sparging with a little extra volume and boiling longer to hit my OG numbers. I've heard of people collecting a couple of extra gallons and boiling that off to help hit OG.

I'm running the 3V Spike system so I fly sparge. Would it be worth it here to sparge a bit longer, collect some extra volume in the BK and boil for an extended period of time to hit numbers? I'm trying to still end up at my desired final volume of 12.5 gallons AND hit my desired OG.

Thoughts?

 

[VikeMan]

Would it be worth it here to sparge a bit longer, collect some extra volume in the BK and boil for an extended period of time to hit numbers?

Whether it would be worth it (to you) is your call. But yes, a longer sparge (i.e. more water) would increase efficiency, and a longer boil would get rid of additional water.

If you do extend your fly sparge, I'd recommend paying (extra) attention to your sparge water's pH. Perhaps consider acidifying it before you begin the sparge, to avoid excessive tannin extraction.

 

[Rob2010SS]

So this is something I have never had to do so just looking for a little clarification.

When you acidify the sparge water, ultimately, the goal is under 6, right?

Is there a calculator to figure out how much acid to add to water to get it to the desired level?

 

[VikeMan]

When you acidify the sparge water, ultimately, the goal is under 6, right?

I recommend aiming for a pH roughly equal to your mash pH. But definitely lower than 6.0.

Is there a calculator to figure out how much acid to add to water to get it to the desired level?

MpH (a free download) includes a sparge water acidification calculator. So does BrewCipher (also free), which has MpH embedded. I'm sure there are others, too.

ETA: If you are sparging with distilled/RO water, there's no need to acidify it.

ETAM:
MpH: Homebrewing Physics
BrewCipher: Library

 

[doug293cz]

What is your desired OG?

Brew on

 

[Qhrumphf]

Depending on how big your stout is, and what your brewing water is like (after any adjustments) it'd be unusual to run into a tannin problem. Roasted malts should keep the pH low on their own, and unless your imperial is not so imperial, it'd likely take some significant excess wort collection (and accordingly very long boil) to get the gravity low enough to be problematic.

Normally I'd say that's good advice. With stouts (especially big ones) I prefer the pH up until fermentation to if anything be on the higher side since it seems to reduce the acrid notes.

 

[Qhrumphf]

With really big beers, if you wanna max your efficiency from your grains, do a partigyle (especially if you blend multiple gyles and don't just rely on 2nd/3rd runnings for the small beer). If I'm doing an English Barleywine or Wee Heavy I often do a respective Bitter or Scottish Heavy in combination.

 

[day_trippr]

fwiw, one can sparge to end of runnings below pH 5.6 and SG > 1.010. When I do my 1.107 OG imperial stout I pull an extra gallon of pre-boil volume just to grab those extra fermentables and take the boil time hit...

Cheers!

 

[RM-MN]

There are two factors necessary for tannin extraction, high pH and high temperature. If you control one the other doesn't matter. That's why people are suggesting to control the pH. That's not always the easiest as you need to monitor the pH or start with the pH lower than necessary so it doesn't rise above the magic 6.0. Why not sparge with cooler water? Hot water doesn't get you any appreciable amount more sugar than cool water and after the sparge through the hot saturated grains it will be much warmer anyway so it won't slow the heating to boil by much either.

You're planning on a low lauter efficiency. That's good to plan for. How about your mash efficiency? Mash efficiency is controlled by two factors too, time and crush quality. With your conventional mash tun, coupled with a fly sparge you are limited in how fine you can crush and still be able to drain the mash tun. Change that to BIAB and a really fine crush drains just as easily as a coarse crush because you have such a large filter area. OK, so you don't want to change to BIAB, you want to use the equipment you spent all that money on. I get it. So for this batch, get a bag or just some Swiss Voille curtain material and line your tun with that. Crush the grain to powder (Ok, not quite that fine) and when the wort quits running because of a stuck mash or sparge, just lift up the bag or curtain cloth to expose more filter area.

 

[Rob2010SS]

I recommend aiming for a pH roughly equal to your mash pH. But definitely lower than 6.0.



MpH (a free download) includes a sparge water acidification calculator. So does BrewCipher (also free), which has MpH embedded. I'm sure there are others, too.

ETA: If you are sparging with distilled/RO water, there's no need to acidify it.

ETAM:
MpH: Homebrewing Physics
BrewCipher: Library

I will be sparging with RO water in which the profile has been adjusted with brewing salts. So no need to acidify?

 

[Rob2010SS]

What is your desired OG?

Brew on

Desired OG is 1.105.

 

[Rob2010SS]

fwiw, one can sparge to end of runnings above pH 5.6 and SG > 1.010. When I do my 1.107 OG imperial stout I pull an extra gallon of pre-boil volume just to grab those extra fermentables and take the boil time hit...

Cheers!

This is exactly what I'm contemplating doing. I just want to make sure I hit my numbers.

 

[VikeMan]

There are two factors necessary for tannin extraction, high pH and high temperature. If you control one the other doesn't matter.

Indeed, both are factors. But tannins are extracted in every mash (and present in every beer, from both malt and hops). Higher pHs extract more. Higher temperatures extract more. And high pHs with high temperatures combine for worst cases. It would be nice if there were a real data based curve to show the combined effect, but I've never seen one. But I don't think it would look like a step function.

 

[Rob2010SS]

There are two factors necessary for tannin extraction, high pH and high temperature. If you control one the other doesn't matter. That's why people are suggesting to control the pH. That's not always the easiest as you need to monitor the pH or start with the pH lower than necessary so it doesn't rise above the magic 6.0. Why not sparge with cooler water? Hot water doesn't get you any appreciable amount more sugar than cool water and after the sparge through the hot saturated grains it will be much warmer anyway so it won't slow the heating to boil by much either.

So this would be something I could do. However, I don't know how to cool the water reasonably quickly once the mash is complete, given my system is a HERMS system. Any ideas on how to do that?

You're planning on a low lauter efficiency. That's good to plan for. How about your mash efficiency? Mash efficiency is controlled by two factors too, time and crush quality. With your conventional mash tun, coupled with a fly sparge you are limited in how fine you can crush and still be able to drain the mash tun. Change that to BIAB and a really fine crush drains just as easily as a coarse crush because you have such a large filter area. OK, so you don't want to change to BIAB, you want to use the equipment you spent all that money on. I get it. So for this batch, get a bag or just some Swiss Voille curtain material and line your tun with that. Crush the grain to powder (Ok, not quite that fine) and when the wort quits running because of a stuck mash or sparge, just lift up the bag or curtain cloth to expose more filter area.

So when I mash, I always use a BIAB bag anyway. It makes removal of the grains much quicker. So I will crush the grains up super fine. I typically do that with impy's anyway. I run the grains through the mill at the LHBS twice.

 

[VikeMan]

I will be sparging with RO water in which the profile has been adjusted with brewing salts. So no need to acidify?

The answer, if a definitive one could be given, would depend on the combined buffering capacity of the wort, the alkalinity of the sparge water, and how far you take the fly sparge. But the first factor is really an unknown. Personally, if I were doing an extended fly sparge with anything but straight RO/distilled, I would acidify. It's cheap insurance.

 

[Rob2010SS]

The answer, if a definitive one could be given, would depend on the combined buffering capacity of the wort, the alkalinity of the sparge water, and how far you take the fly sparge. But the first factor is really an unknown. Personally, if I were doing an extended fly sparge with anything but straight RO/distilled, I would acidify. It's cheap insurance.

So when you say straight RO water, are you implying to NOT adjust the profile of that water? That would get me to a point where I would not have to acidify?

 

[VikeMan]

So when you say straight RO water, are you implying to NOT adjust the profile of that water? That would get me to a point where I would not have to acidify?

Yes, that would work. Plain RO/distilled water has basically no buffering capacity, so it won't raise your runoff pH significantly. Also, the deleted salts can be added in the kettle for flavor/moutheel, if desired.

I'm assuming that the salts you were going to add included Baking Soda or Slaked Lime, which are typically used to raise the mash pH in otherwise acidic grain bills (e.g. stouts). If not, i.e. if the only salts you were using are ones that lower (or have no affect) on mash pH, then there would be no reason to avoid them in the sparge.

 

[Rob2010SS]

Yes, that would work. Plain RO/distilled water has basically no buffering capacity, so it won't raise your runoff pH significantly. Also, the deleted salts can be added in the kettle for flavor/moutheel, if desired.

I'm assuming that the salts you were going to add included Baking Soda or Slaked Lime, which are typically used to raise the mash pH in otherwise acidic grain bills (e.g. stouts). If not, i.e. if the only salts you were using are ones that lower (or have no affect) on mash pH, then there would be no reason to avoid them in the sparge.

You are correct. For baking soda, I transfer my strike volume over to the MT and add the baking soda to only the mash water. The sparge water only sees the other salts - gypsum, calc chlor., salt, epsom salt, mag chlor, etc.

So I can add those and be fine with not having to acidify the sparge water?

 

[VikeMan]

So I can add those and be fine with not having to acidify the sparge water?

Yep.

 

[RM-MN]

So this would be something I could do. However, I don't know how to cool the water reasonably quickly once the mash is complete, given my system is a HERMS system. Any ideas on how to do that?

From where do you get your RO water for sparging? Does it need to go through the HERMS?

 

[Rob2010SS]

From where do you get your RO water for sparging? Does it need to go through the HERMS?

I have a Buckeye Hydro RO system in my basement that hooks up to a sink. I run the output hose to my HLT and fill the HLT with 20 gal of RO water.

However, while the HLT is filling, I have a 6 gal carboy and about 7 single gallon jugs that I fill with RO water as well. This water is what I use to top up the HLT during the mash to (1) get the water level high enough to fully utilize the HERMS coil and (2) to cool off the HLT for the mash recirculation.

 

[doug293cz]

Desired OG is 1.105.

Ran a simulation with a triple batch sparge (not quite as efficient as a good fly sparge, but can't simulate fly sparge), 1.25 qt/lb mash thickness, 3.75 gal total boil off (1.25 gal/hr for 3 hrs), and 12.5 gal post boil volume. If you can get 100% conversion of the grain, you can achieve in excess of 76% lauter (and mash) efficiency. Grain required was 49.1 lb. Mash volume (grain + water) was 19.3 gal.

At 92% conversion, mash efficiency dropped to 65%, grain required went up to 57 lb, and mash volume went up to 22.4 gal.

Getting a high conversion efficiency is critical for making very high OG worts, without having to add extract to the boil.

Brew on

 

[Rob2010SS]

Ran a simulation with a triple batch sparge (not quite as efficient as a good fly sparge, but can't simulate fly sparge), 1.25 qt/lb mash thickness, 3.75 gal total boil off (1.25 gal/hr for 3 hrs), and 12.5 gal post boil volume. If you can get 100% conversion of the grain, you can achieve in excess of 76% lauter (and mash) efficiency. Grain required was 49.1 lb. Mash volume (grain + water) was 19.3 gal.

At 92% conversion, mash efficiency dropped to 65%, grain required went up to 57 lb, and mash volume went up to 22.4 gal.

Getting a high conversion efficiency is critical for making very high OG worts, without having to add extract to the boil.

Brew on

So my grain bill is 55.51 lb of grain and my mash thickness is 1.1qt/lb. That takes up roughly 19.71 gallons of space in my 20 gal MT.

To help with conversion of the grain, I'm looking at doing...
1. Double mill of the grains, as I use a BIAB bag in the mash tun.
2. 90-120 min mash

Anything else I should be doing?

 

[VikeMan]

I'm not familiar with your spike Mash Tun, but if there is any non-recoverable dead space, that will also affect (decrease) mash efficiency.

 

[doug293cz]

I'm not familiar with your spike Mash Tun, but if there is any non-recoverable dead space, that will also affect (decrease) mash efficiency.

This is true for batch sparging, but I'm not sure it plays much of a role in fly sparging, since in a traditional fly sparge, the mash tun is left full of dilute wort. However, if you stop the sparge after a specific volume, and then drain "all" wort, then undrainable volume would play a role.

Brew on

 

[Rob2010SS]

I'm not familiar with your spike Mash Tun, but if there is any non-recoverable dead space, that will also affect (decrease) mash efficiency.

How would one account for that? I typically have just sucked that up as a loss and just reduced my planned mash efficiency to account for it. There is dead space in there for sure. I want to say I had read somewhere that it's like half a gallon of dead space in there but I'm not 100% sure on that as I've never measured it myself.

 

[doug293cz]

So my grain bill is 55.51 lb of grain and my mash thickness is 1.1qt/lb. That takes up roughly 19.71 gallons of space in my 20 gal MT.

To help with conversion of the grain, I'm looking at doing...
1. Double mill of the grains, as I use a BIAB bag in the mash tun.
2. 90-120 min mash

Anything else I should be doing?

You can monitor the the level of conversion using the method here.

Brew on

 

[VikeMan]

How would one account for that? I typically have just sucked that up as a loss and just reduced my planned mash efficiency to account for it. There is dead space in there for sure. I want to say I had read somewhere that it's like half a gallon of dead space in there but I'm not 100% sure on that as I've never measured it myself.

With batch sparging (or "no sparging"), the math is fairly straight forward. I'm not sure you can really compute it with a fly sparge without knowing exactly how much/fast your sparge water is mixing with the the wort (vs. the unattainable ideal of the sparge water simply "pushing" the wort out). With fly, I'd say the easiest way to predict efficiency (including the impact of dead space) might be to plot actual attained efficiencies by grain bill size and find a best fit curve.

 

[doug293cz]

With batch sparging (or "no sparging"), the math is fairly straight forward. I'm not sure you can really compute it with a fly sparge without knowing exactly how much/fast your sparge water is mixing with the the wort (vs. the unattainable ideal of the sparge water simply "pushing" the wort out). With fly, I'd say the easiest way to predict efficiency (including the impact of dead space) might be to plot actual attained efficiencies by grain bill size and find a best fit curve.

I got some data in the past from an experienced fly sparger, and their lauter efficiency was typically about 3 percentage points higher than the theoretical from a triple batch sparge. I then make the assumption that lauter efficiency for fly sparging will follow a very similar curve to triple batch sparge as grain bill size (relative to pre-boil volume) increases. This makes some sense since you can think of a fly sparge as being analogous to an infinite number of infinitesimally small batch sparges.

Brew on

 

[Vale71]

It really depends on what your last running's OG is. If it's still quite high there is something to be gained from an extended sparge and boil, if it's already mostly water than it's a waste of time and energy at best. I would plan on the extended mash and boil only on a contingency basis by having a couple of gallons extra sparge water ready. When you're nearing your target volume you should take a sample of the runnings, stop the sparge, measure its OG and then decide whether to go with the extended sparge.