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Brews & Views Bulletin Board Service * Brews and Views Archive 2011 * Archive through July 05, 2011 * Using pump & batch sparge. Changes in efficiency? < Previous Next >

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Extract and volume 05-21-11  06:30 pm
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Todd Metcalf
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Registered: 05-2011
Posted From: 24.91.175.10
Posted on Thursday, May 19, 2011 - 03:59 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

I've been doing batch sparges for several years now. When draining the mash tun, I've always just opened the valve fully. Reading around here, others haven't seen a benefit/gain to slowly draining during batch spaging.

I got sick of moving heavy kettles so last session, I introduced a pump. When draining the mash tun, the flow rate was greatly increased with the pump compared to just gravity as before.

I noticed I had a big drop in efficiency (60 compared to low 70s w/o pump). When I've had a drop like this, I usually can attribute it to not bringing the mash-out temperature high enough. But never such a bad difference.

Do you think adding a pump, which sped up the sparge, was a factor?
 

Bill Pierce
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Posted From: 24.150.49.181
Posted on Thursday, May 19, 2011 - 04:58 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

If all other variables are the same, I wouldn't expect the efficiency to change because you added a pump to the system. I assume that after each batch of sparge water you are stirring the mash, waiting a few minutes and then recirculating the runoff until it is relatively clear.
 

Denny Conn
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Username: Denny

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Posted on Thursday, May 19, 2011 - 05:10 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

I agree with Bill. The only way to really know is to brew the same recipe with the same bag of malt and mill both with and without a pump.
 

Graham Cox
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Username: T2driver

Post Number: 2731
Registered: 11-2004
Posted From: 72.15.105.173
Posted on Saturday, May 21, 2011 - 03:44 am:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

Todd, do you have some sort of regulator, like a ball valve, on the output of your pump? I'm no pump expert, but I own and regularly use the standard homebrew March magnetic pump. I don't think it impossible that introducing suction on your mash would affect your efficiency, or even improbable, with great respect (and affection ) for my learned colleagues above. I think serious suction would encourage channeling through, and probably around, the grain bed, which would greatly decrease efficiency as you described.

I would consider just brewing another normal batch, but throttling your pump way back to what would approximate a gravity runoff, and see how that works. You wouldn't get a definitive answer from just one trial, but you might get an idea.
 

Pete Webb
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Registered: 07-2003
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Posted on Saturday, May 21, 2011 - 04:45 am:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

I respectfully disagree. Channeling should only be a factor if fly sparging.
 

Graham Cox
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Username: T2driver

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Posted on Saturday, May 21, 2011 - 05:08 am:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

I respectfully disagree with your disagreement. Pressure from above or suction from below would tend to favor the same thing, that being the easiest path. If there are cracks, fissures, spaces outside the mass, etc., it doesn't matter if pressure is applied from above or if suction is applied from below - the wort is going to seek the easiest path out in an attempt to establish equilibrium of pressure.
 

The Jolly Brewer
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Posted on Saturday, May 21, 2011 - 07:07 am:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

But the idea with batch sparring is that the sugars are in solution and you are not rinsing as in a fly sparge so channeling should theoretically not be an issue.
 

Steve Jones
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Posted on Saturday, May 21, 2011 - 01:44 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

Graham, I respectfully disagree with your respectful disagreement with Pete's respectful disagreement with you.

Supposedly when you batch sparge the liquid in the mash is at equilibrium with the grain as far as sugar content goes. Pressure or vacuum doesn't even enter into the equation. Whether you drain slowly or quickly the runnings should be at the same gravity.

That is one reason why you need to let the second batch set for 15 minutes or so ... to let the sugars equilibrate between the grain and liquid.
 

Graham Cox
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Username: T2driver

Post Number: 2733
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Posted on Saturday, May 21, 2011 - 02:25 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

Steve, what I'm speaking of is channeling. In a slow lauter, whether it be batch or fly sparging, the wort has an opportunity to seek out an infinite number of paths through the semi-fluffy grain bed, which provides for a thorough rinsing of the husk material. If you introduce WAY too much water in a fly sparge, the weight can compact the grain bed to the point that it is no longer expanded like a wet sponge, but flattened. The wort then has less opportunity to diffuse through the grain bed and will instead go around it or though cracks - again, the easiest path - and efficiency will suffer.

In batch sparging, in theory all of the liquid should have a homogeneous content of wort sugars, but those sugars are not irretrievably bound to the water - they're simply in suspension. My belief is that if you collapse the grain bed via mechanical means, e.g. a wide-open pump, some of those sugars may be trapped in the husk material, which is now serving not as a filter but as a barrier.

Whatever the case may be, there are other possible explanations for the efficiency drop, such as a poor crush, high-gravity wort, etc. Without examining and/or eliminating the rest of the variables, we only have one part of the equation.
 

Bill Pierce
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Posted on Saturday, May 21, 2011 - 03:06 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

Graham, with all due respect, I don't see how the sugars are in suspension in the sparge water. In terms of the physical chemistry it's a solution.

If what you say were true (the sugars are trapped in the husk material), then the volume of runnings in the kettle (the pre-boil volume) would also be less than expected.

(Message edited by BillPierce on May 21, 2011)
 

Graham Cox
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Posted on Saturday, May 21, 2011 - 03:30 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

Yes, Bill, but it is not a pure and simple solution, such as sucrose uniformly dissolved in a glass of hot water.

I'm almost done with a grain science textbook, which is interesting both from a brewing and a baking viewpoint. If you look at a scanning electron micrograph of the various grain constituents - husk, bran, etc. - it's not the lovely, smooth picture you would imagine, but a labyrinth of channels and jagged outcroppings. Lots of traps. And yes, trapping sugars also entails trapping liquid, so the pre-boil volume would be less.
 

Graham Cox
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Username: T2driver

Post Number: 2736
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Posted From: 72.15.105.173
Posted on Saturday, May 21, 2011 - 07:46 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

To further explain my thinking: I think we all agree that fly sparging produces marginally more extract than batch sparging, which produces more extract than no-sparging. In batch sparging or no-sparging, if the soluble sugars were so eager to leap into solution and be carried out of the tun, without regard to the path they take to get there, why isn't batch sparging more efficient than fly sparging? Why isn't no-sparging just as efficient as batch-sparging? If batch sparging produces less extract for a given mash than fly sparging, where did those extra sugars that were lost go? Are they adhering to the sides or bottom of the tun? No, they are still in the grain bed.

To take it a step further, why do we even sparge at all? If all of the available sugars go into solution, wouldn't it be logical that they would all rush out in the first runnings? Clearly they do not. Where then do they go? They're still in the grain bed.

If it didn't matter what path the liquid took in a batch sparge, then batch sparging would be inherently more efficient than fly sparging. It's not. Despite our best efforts at mechanical agitation of the mash, a quick and asymetrical draining is not going to capture all of the available sugars. Now, collapse the grain bed with a suction pump pulling from one point in the tun and in my mind, your further compromise the dynamics of the system.
 

Bill Pierce
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Posted on Sunday, May 22, 2011 - 03:57 am:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

Graham, the reason fly sparging is marginally more efficient than batch sparging, and no-sparge brewing considerably less efficient, is the gravity of the liquid that remains in the mash tun. In the case of the fly sparging, the gravity of the final runnings is typically 1.010 - 1.012, while in a two-batch sparge it is about 1.020 - 1.022. It's difficult to say what the gravity of the final runnings are with no-sparge brewing (it depends on both the gravity of the first runnings and how much water is added). At any rate, with batch sparging and no-sparge brewing, more sugar remains in the liquid left in the mash tun. Because this liquid is discarded with the spent grain and does not contribute to the beer, it results in lower efficiency.

Stripped down to the basics, it's really no more complicated than that.

Why do we sparge? Because if we didn't we would be discarding good extract that we can use to make good beer. Now if nearly 100 percent efficiency were the goal, we would grind the grist to the finest powder, find a way to avoid a stuck mash and sparge until the gravity were on the order of 1.002. Of course the quality of that beer would suffer considerably (tannins and other harsh grainy flavors from the husks).
 

Graham Cox
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Username: T2driver

Post Number: 2737
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Posted on Sunday, May 22, 2011 - 04:32 am:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

And thus I think we make the same point, Bill. It is clear that under various circumstances, the grain bed will variously serve as (a) a filter, (b) a convoluted labyrinth, or (c) a barrier. Ideally, no matter what method of brewing and sparging we use, obviously (a) is the goal we wish to utilize, or perhaps (b) in the extreme. I think the most efficient method of facilitating (a) is to use gravity, which flows straight down. A suction pump does not. Excessive water on top, the weight of which collapses the grain bed, may not.

This is not egghead theory on my part, I batch-sparged over 120 batches, so I know whereof I speak. I never fed from my tun via powered suction, however, so that part is theory. I'm quite comfortable with mine, with respect to dissenters.
 

Joe Rovito
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Posted on Sunday, May 22, 2011 - 05:48 am:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

Wow, what a great thread - thanks Todd. There was something similar on the digest may years back, and at one point, I was half-convinced batch sparging could actually increase efficiency.
Bill makes an excellent and simple to understand point - if there's gravity (sugar) in your tun, it's not in your wort.
But maybe, as Graham implies, the runnings you measure are not really representive of the average gravity in the grain bed. That is, the equilibrium that Steve asserts does not exist.
I hope you guys can figure this out, 'cuz I'd like to try to get my efficiency out of the sixties. Sounds like a pump vs. gravity drain experiment is in order.
 

Bill Pierce
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Post Number: 12963
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Posted on Sunday, May 22, 2011 - 01:45 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

I'm still not absolutely convinced the pump is the culprit. Most commercial breweries rely on pumps for sparging, and the efficiencies achieved by typical small craft breweries (anything over 80 percent is considered very good) are very much in line with those experienced by homebrewers. It is true that batch sparging is rare in a commercial setting.

Moreover, most homebrew batch spargers open their mash tuns all the way and drain the runnings quickly; the reduced time is considered one of the advantages of this method. But the pressures and diameters involved are modest. A typical homebrew mash tun has a grain bed depth of a couple of feet at most, the plumbing is one-half inch or less in diameter, and the gravity drop from the mash tun to the kettle is no more than a few feet.

I suppose the operative question here is whether a pump so increases the pressure as to prevent uniform draining of the mash runnings and pockets of undrained extract in the grain bed. Again my contention is that this is highly unlikely given the geometry of homebrew mashing and the modest flow rate of pumps used by homebrewers.

But I'm willing to consider Graham's hypothesis. Yes, it would take a somewhat controlled experiment (the same recipe from the same lot of base malt ground with the same mill, and use of a pump for sparging in one case and gravity in the other) to determine this with some certainty.
 

Steve Ruch
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Posted From: 209.240.206.208
Posted on Sunday, May 22, 2011 - 03:01 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

What is the actual difference between fly and batch? If fly would give 1.050 what would batch of the same grains give?
 

Graham Cox
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Post Number: 2739
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Posted on Sunday, May 22, 2011 - 03:21 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

That depends on several factors, Steve, many of which are related to tun design, but all things being equal, not much. If a homebrewer achieved 75% efficiency fly-sparging, all other things being equal, he'd probably achieve 70-72% batch-sparging. The small loss in efficiency is offset by the savings in time and effort.

As has been previously discussed here and in other threads, at our level, compensating for lower efficiency with another pound of grain is of little consequence, and again, the savings in time is worth it to most homebrewers who choose to batch-sparge. On a commercial scale, however, a couple of efficiency points translates into hundreds, thousands, or even millions of dollars over a year of production.
 

Denny Conn
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Posted on Sunday, May 22, 2011 - 04:28 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

Steve, likely the same, but there are too many other variables ti know for sure.

Graham, while I appreciate your speculation, my direct personal experience contradicts it. And I don't know how you can possibly expect the efficiency figures in your last post to be realistic. I can use the exact same recipe as fly spargers and achieve higher efficiency. As I said, there are too many pother variables to be able to make a blanket statement.
 

Bill Pierce
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Post Number: 12965
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Posted on Sunday, May 22, 2011 - 05:30 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

In theory batch sparging should result in slightly lower efficiency, as there is a little more extract left in the mash tun that is discarded with the spent grain. However, actual reports from homebrewers, including Denny, occasionally indicate slightly higher efficiency. Obviously there must be other factors, which lends some credence to Graham's explanation. However, I tend to think it's a matter of measurement. Accurate efficiency calculations require rather careful measurement of gravity and volume. An error of a single gravity point or volume as little as 0.1 gallon is enough to change the results. Additionally, we usually use average values for extract potential rather than the specific fine grind dry basis results for the particular lot of base malt.
 

Graham Cox
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Username: T2driver

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Posted on Sunday, May 22, 2011 - 06:43 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

Denny, using the same recipe doesn't offer any meaningful comparison - you'd have to use the same or identical equipment, to include the mill, but sparge in different ways to make such a comparison.

The numbers I used generally reflect my own experience using both methods, and are typical of numbers reported by many, if not most homebrewers. That may not be your experience using your methods and your equipment, but general consensus in the literature and in industry practice supports them.
 

Kevin Whyte
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Posted From: 24.14.48.109
Posted on Sunday, May 22, 2011 - 06:47 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

I have always thought of this by analogy with coffee, which I know better.

Fly sparging is like a standard drip coffee maker : ideally, each drop of water travels through the bed to get fully saturated and then comes out the other side. If done perfectly this will extract everything that there is. The main problems are that not all paths through are equally likely, so some spots get missed (low efficiency) and other get too much water going through (overextraction).

Batch sparging/no sparging is like a french press. All the water mixed in, stirred, and left to reach equilibrium. Then the liquid is separated from the spent material. Unless done quite badly, everything should be uniform and so there's much less risk of overextraction. The downside is that the equilibrium between water and material isn't full extraction, so some potential is left behind. For coffee making that's essentially always just compensated for by using extra, and no-sparge brewers do the same. A second batch mostly fixes this problem. In theory one could do more batches to get everything, but the reduced efficiency of the process would still show up in the extra volume that would result.

For coffee, overextraction is a major flavor problem and getting anything like uniform flow through the bed almost impossible, hence drip coffee makers simply don't do as good of a job. I've always been surprised that fly sparging works as well as it does - it just goes to show the analogy isn't perfect.

For the OP, unless you're getting less volume than before (and so leaving more in the mash tun) I can't see how channeling while batch sparging could have any significant effect on efficiency. My best guess is that you weren't leaving the batch sitting long enough to get full extraction before starting to drain, and that the speed up from the pump has just made that worse.
 

Steve Ruch
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Post Number: 246
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Posted From: 209.240.206.200
Posted on Monday, May 23, 2011 - 02:43 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

Gotta try batch and see for myself
 

Todd Metcalf
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Posted on Tuesday, May 24, 2011 - 01:27 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

WOW, I've been away from the forum for a week. This thread definitely got some attention.

Besides adding a pump, I should have mentioned in the original post that there was another big variable with this brew session compared previous sessions. This thread has gone on so well with the pump/sparge speed that I feel bad about giving this information this late in the discussion.

I usually do 5 gallon batches, but this session I was doing 10 gallons. It was pushing my mash tun's limit for mash size. When I look back, because the mash tun was filled to the brim, I may not have stirred the sparges (1st & 2nd) as much as I had done in the past. This would go inline with some of the messages in the thread. Especially the 2nd sparge, I didn't get the sugars into the solution as well as I could have.
 

Bill Pierce
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Username: Billpierce

Post Number: 12973
Registered: 01-2002
Posted From: 24.150.49.181
Posted on Tuesday, May 24, 2011 - 01:52 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

At least you provided the likely answer, Todd, and you gave us an interesting and engaging topic for discussion. That's not a bad thing at all.