Mash Thickness in rect. cooler mash tun

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Mash Thickness in rect. cooler mash tun

Postby shaggyt » Sat Aug 29, 2009 1:55 pm

So I'm about to embark on my first 10 gallon batch using my newly converted cooler as a mash tun. In the past when fly sparging, I've used the 1.3qt/lb ratio for my mash with good results.

Now that I'll be using a new system and batch sparging, I'm wondering if I need to adjust my mash thickness.

Does batch sparging benefit from a thicker mash or a thinner mash?

My thoughts are that a thicker mash translates to more sparge water, which then will be halved into 2 sparges. As such, does a majority of the extraction occur during the mash or the sparges?

I realize this might just be an opinion question based on experience, but I like to hear other perspectives/results.

Cheers.
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batch sparge efficiency

Postby slothrob » Sun Aug 30, 2009 9:36 am

There's been quite a bit of research done on this. There's a slight advantage to having equal runnoff volumes (either for one or 2 sparges). It can increase your efficiency by a few percent, but there's about a gallon window before it starts to make a difference. After that, efficiency should go down with more mash water or sparge water.

You may see a slight improvement in efficiency, a few to maybe as much as 5%, with a second sparge.

Kai Troester has done quite a bit of research on efficiency.
Here is a good analysis of factors affecting efficiency as a function of batch sparging variables.

Here is a great set of experiments that demonstrate the effects of mash parameters on efficiency and attenuation. One of the most interesting observations is the benefit of thinner mashes, as is typically used by Germen breweries. There have been a few other experiments that show efficiency improvements with mash thicknesses in the 1.5 to 2.25 qt/# range. This is thought to be due to improved starch gelatinization, I believe. You may well gain more from a thinner mash than you would by moving that volume to a thinner sparge.

Similarly, step mashes that have a final 15+ minute rest in the 155-162°F range can show an increase in efficiency due to improved starch gelatinization at the higher temperatures and a last rapid burst in enzyme activity before they become denatured.
Last edited by slothrob on Wed Sep 02, 2009 6:16 am, edited 1 time in total.
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One-sparge is supposed to be most efficient

Postby billvelek » Tue Sep 01, 2009 6:46 pm

Thanks for the links, Slothrob. I don't have the time right now to really digest the info -- which looks very intriguing and useful -- but I'm going to make a point of studying it as soon as I have a chance. Meanwhile, let me add that I was involved in a discussion about batch sparging with Denny Conn, among others, in another forum. Seems like it was rec.crafts.brewing. Anyway, I'm pretty sure that it was Denny Conn who stated that efficiency is maximized by doing only a single-sparge, i.e., first runnings + one batch sparge, and that sparge water is divided so that enough of it is added to the mash before first runnings are drained in order to drain approximately equal volumes. E.g., if your target is 6.5 gallons of wort pre-boil, then you'd be aiming for 3.25 gallons of first runnings, and 3.25 gallons from the first (and only) sparge. Now, that all seemed very counter-intuitive to me, but I worked out the math and became convinced that he is correct. Unfortunately I became very busy with other matters and then the weather turned very hot earlier than usual, so I haven't had a chance to actually try it and measure the results.

At any rate, here is Denny's webpage about it: http://hbd.org/cascade/dennybrew/ -- however that page contains broken links to the works of Ken Schwartz and Bob Regent. I spent a little bit of time trying to find them, and this is what I came up with so far:

http://www.bayareamashers.org/content/maindocs/BatchSparging.htm -- I _think_ that is is Bob Regent's page, but there is no identity of the author.

http://home.roadrunner.com/~brewbeer/files/nbsparge.html -- Ken Schwartz's page.

Cheers.

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Batch sparge efficiency

Postby slothrob » Wed Sep 02, 2009 7:46 am

I took the time to go through the math, too, and equal volume runnings are theoretically most efficient. There's quite a bit of a window, though, and the volumes need to be more than 10% from that equal volume before it makes more than a percent or two difference in efficiency.

It's not so much that 1 sparge is most efficient, but that the theoretical efficiency gain from an additional sparge is no more than a few percent. For most of my single infusion recipes I just mash in with a volume that will give me half my pre-boil volume when drained.
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Glad I asked

Postby shaggyt » Wed Sep 02, 2009 9:13 am

Thanks for the info gents...the links provided definitely helped.

I ended up using two 5 gallon sparges and came very close to my predicted OG after the boil (two points off). So until I obtain a Barley Crusher, I'll probably continue with two sparges.

I also need to find the time to work through the math.

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Malt Water Absorption: is BTP wrong?

Postby billvelek » Wed Sep 02, 2009 9:38 am

I've changed the subject line, but this is essentially a continuation of what we have been discussing in this thread about batch sparging efficiency. However, I want to get some thoughts about BTP's "Malt Water Absorption" 'preference setting' and some comments made in the link provided by Slothrob to the 'braukaiser' article on "Batch Sparging Analysis" -- http://braukaiser.com/wiki/index.php?title=Batch_Sparging_Analysis#Formulas.

My BTP program has the absorption rate set at .48 quarts/pound -- which I am pretty sure is the default setting because I can't remember ever changing it or why I would have, because I have no idea how much water is absorbed by grain; I checked the user guide and it does not list a default value but it does have a screen shot which indicates one liter per kilogram which equals 1.06 quarts per 2.20 pounds = .48 quarts/pound. Okay, so what's the problem? Well, the braukaiser article says this: "One note regarding the grain absorption rate: Many brewing water calculation programs and other sources cite a grain absorption ratio of around 0.12 gal/lb ..." which of course is the same as .48 quarts/pound "... but the experiments here assume a grain absorption ratio of about 0.19 gal/l (1.56 l/kg). The difference stems from the fact that the extract (mainly sugars) that is dissolved in the wort during mashing actually increases the volume of the wort at a rate of about 0.63 l/kg (0.3 qt/lb). But that is ignored by computer programs that determine the amount of water needed. They assume that the volume difference between resulting pre-boil wort and the water used for mashing and sparging must have been left in the grain. But since the volume increase by the extract has been neglected, the amount of wort left in the grain is underestimated. While this works for calculating the water needed for brewing it results in unrealistically low amounts of wort left in the grain and higher lauter efficiencies. Hence the calculations here were done with a more realistic absorption factor of 0.19 gal/lb"

Now, if that comment in 'braukaiser' is accurate, then it would seem that we ought to change our malt absorption settings, and BTP ought to change its default setting so that the uninformed user can get a more accurate result -- at least for purposes of calculating efficiency. On the other hand, changing it would alter the volumes of water additions and the resulting pre-boil volume, which we obviously don't want to do -- and I have been getting very accurate results with BTP as far as volumes and temperatures go. I am not a scientist so I'm not sure whether the 'braukaiser' article is accurate. Any comments would be appreciated. Meanwhile, I'm too busy with other things right now to permit me to investigate further, but I hope to have some time tonight to play around with this.

Cheers.

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Re: Malt Water Absorption: is BTP wrong?

Postby slothrob » Wed Sep 02, 2009 10:33 pm

billvelek wrote:Now, if that comment in 'braukaiser' is accurate, then it would seem that we ought to change our malt absorption settings, and BTP ought to change its default setting so that the uninformed user can get a more accurate result -- at least for purposes of calculating efficiency.

This is covered somewhat in Daniels' Designing Great Beers (somewhere around page 63, if I recall correctly) and it can be a bit confusing. For the efficiency calculations we perform, however, 0.12 gal/# is going to give you an accurate result. This is because, as Kai discusses, the effective volume absorbed is ~0.12 gal/# due to the volume increase from the sugar dissolved if you get a typical efficiency. Using Kai's 0.19 number and mash efficiency would allow you to predict the effective absorption, but it would come out close to 0.12 for most brewers.

For Kai's purposes he needs to consider the actual absorption, since he is calculating conversion efficiency. For these calculations he needs to consider the total volume in the mash, which is the runoff volume + the volume of dissolved sugar + the absorbed volume.

I think that the ability to calculate conversion efficiency and lauter efficiency, in addition to mash efficiency, would be a great addition to BTP, in the future. I've been meaning to suggest this as a feature request. These are great tools for troubleshooting your mash.

As it stands, however, BTP isn't wrong so much as simplified.
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Thanks for reply, Slothrob ... but

Postby billvelek » Fri Sep 04, 2009 5:22 am

Thanks for your reply, Slothrob. It has been a long time since I read Ray's book -- which is a shame because it really is great, and I ought to be reviewing it all the time; however, since I use BTP and have the basics down very well from my years of brewing, I'm probably over confident and think I don't need a reference work when brewing or the need to review. Anyway, I got Ray's book off the shelf and dusted it off, and you were pretty close on the mark -- he begins his discussion of water on page 63, exactly. I went ahead and re-read that part of the book, but unfortunately don't have the time right now to dig around in it to see if it contains answers somewhere else. I've got a lot on my plate right now.

Anyway, after reviewing that entire chapter 8, pages 63 to 71, I can't find the same sort of an answer that you've indicated, but since you refer to that specifically, maybe I'm just a bit dense -- a distinct possibility. He begins by talking about water content in weight rather than volume, and how the weight of 'spent' grains is reduced to about 40%, and how that makes up 20% of the weight of the wet grain bed after draining. He later talks about volume when he mentions evaporation, deadspace, and shrinkage, but I can't find where Ray says anything about expansion of volume due to dissolved sugars and how that alters the figure of what is retained in the grains, which is what we are speaking about in this thread. Maybe I just missed the obvious. I see losses due to hop debris and shrinkage in volume as the wort cools, but then the rest of the chapter is about pH and salts.

Could it be in another chapter or in another book? My copy was printed in 1996.

Anyway, I think your answer does make sense, and from a practical standpoint, we just want to make good beer and get the best efficiiency at the same time, regardless of what that actually is or what BTP indicates.

EDIT to add P.S.: I realized that perhaps because Ray was speaking about WEIGHT of water retained in the grain bed -- which logically would vary depending upon the gravity -- I felt compelled to review that info again. I can't see where he differentiates anything based on gravity, and he even gives a table of weights (table 8.1 on p. 64) which seems to be based on plain water without considering gravity. But I can see how the gravity will make a difference although it gets more complicated here. First, it is the gravity of the wort remaining in the grain when we are finished that we need to know -- as opposed to our predicted gravity. Second, it seems to me that if one is batch-sparging, that would be almost precisely the gravity of the final runnings (allowing for a possible minute difference due to sugars inside and outside the grains not fully equalizing) ... but if one is fly-sparging, the sugar content at the top of the grain-bed will necessarily be less than the sugar content at the very bottom of the grain bed (which should equal about the same gravity as the last drops that come from the end of the sparge), and will be affected by any channeling (which is not a factor with batch-sparging). So it would seem nearly impossible to be very accurate on the sugar content of the entire grain bed when fly-sparging, while batch-sparging on the other hand should be fairly accurate. I think this would all be very problematic for BTP unless it uses a different approach. But I find it very interesting to discuss. The main thing is that BTP allows the user to change 'efficiency' -- and in fact will change it automatically when the user changes the final gravity to what the actual measurement is. But aside from BTP, this raises a few more questions in my mind ... but I'll save them for another time.

Thanks.

Cheers.

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water lost

Postby slothrob » Fri Sep 04, 2009 7:17 am

Sorry, Bill, I recalled that chapter as having more of the information needed to do the calculations required to understand Kai's theories. It seems it has the basis for the 0.2 qt/# number and the grain weight decrease with lost sugar, but I got the volume increase from some where else.

I think I might have found the numbers for the volume increase that I used in the calculation from a wine website that mentions that 1 # of sugar added to wine increased the volume by 1 cup. I think it might be more accurately 1 kg of sugar increasing the volume by 632 mL (or 0.076 gallons / #), but I've also seen 645 mL/kg and might have used that number in some of my calculations.

There's still some math to get from Daniels' 0.2 to 0.12. There's a good discussion of this in this thread on efficiency. You can see some of my stumbling in learning this (around pages 4 and 5). There's some fun calculations for different types of efficiencies based on Kai's theories.
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Re: water lost

Postby billvelek » Fri Sep 04, 2009 6:19 pm

slothrob wrote:snip ... There's still some math to get from Daniels' 0.2 to 0.12. There's a good discussion of this in this thread on efficiency. You can see some of my stumbling in learning this (around pages 4 and 5). There's some fun calculations for different types of efficiencies based on Kai's theories.

Thanks, Sloth. Found it but there are quite a few long posts there, and I don't have time right now because I've got to run somewhere right now. Meanwhile, if you're interested, I've started a thread about all of this on Usenet: rec.crafts.brewing -- in case you visit there. Seems like they have a bit more traffic there than here.

Cheers.

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