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  • Filter bed

    I recently had a conversation with another brewer about filter bed thickness (grain bed in lauter tun, not the stainless structure) and the optimal bed thickness to get a maximum yield and smooth, speedy filtration.

    I know there are other variables as temperature, milling,... but leaving those out what is your take on optimal bed thickness.

    We have made some calculations and researched the theory but I would like to get your feedback and input on this.

    BelgianBrewer
    Last edited by BelgianBrewer; 04-04-2008, 05:37 PM.

  • #2
    I would venture that the depth is highly dependent on whether it is a pumped mash (one vs. multiple vessel mash/lauter), and if there are knives used during lauter. The pumped mash would have less air and be denser and slower to lauter, a Steel's masher feeding a single vessel and a floating lauter could support a thicker mash bed for the same lauter speed.
    When my single vessel mash was a meter deep, I was not very happy. Currently mine vary from 0.5 meters to 0.75 meters and I get off work earlier.

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    • #3
      The bed thickness is highly dependent on the type of mill you have.

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      • #4
        Originally posted by crassbrauer
        The bed thickness is highly dependent on the type of mill you have.
        I'm sure it all depends on your lauter size/shape as well! At a guess, ours is usually about a meter deep, though I've never actually measured it...this being around a 15 bbl batch.
        www.devilcraft.jp
        www.japanbeertimes.com

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        • #5
          Measuring shear

          Originally posted by Moonlight
          I would venture that the depth is highly dependent on whether it is a pumped mash (one vs. multiple vessel mash/lauter).... The pumped mash would have less air and be denser and slower to lauter,
          I would think the pumping would infuse more air but tend to shear the grain and re-distribute it with more "packing force" and lead to a compact bed.

          That said, anyone ever dried spent grain and compared that to the milled grain in a sieve test? Is there a standard for an acceptable difference?

          BTW-we pump over our grain, have a thick bed and have lauter (Kettle-up OG) problems.
          Brewmaster, Minocqua Brewing Company
          tbriggs@minocquabrewingcompany.com
          "Your results may vary"

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          • #6
            bed thickness and mill

            Lauter bed thickness is dependent upon the type of mill you have. If you have a dry, two-roll mill, your bed will tend to be more compact, because the hulls are broken in the mill. If you have some sort of wet mill, they'll become elastic before milling and generally remain whole and therefore improve your grain bed by increasing the bed volume.

            The bed thickness for a dry, two roll mill should generally be around 12 - 15 inches, whereas with most types of wet mills, the thickness will reach 20 -25 inches. Some of you may think this is too short; however, if you take a look at a brewhouse with a dedicated lauter tun (i.e. no combi-vessel), you'll notice that it is usually the vessel with the largest diameter in the brewhouse, and for good reason.

            When brewing British or American ales, the type of lauter tun, and therefore also the mill, are less important, because ales are a little more rough around the edges than lagers (not meant in a negative way, they just are). Combi-vessels aren't such a problem, because most ales are brewed with a single temperature mash. "Huskiness" and "grainy-ness", among other things, like the bitterness from fertilized hops, hot-side aeration, etc., etc. are covered up by ales' more complex sweetness and by the yeast by-products of top-fermenting yeast. Ales are great for this reason. It's what makes them what they are. The bed depth can be higher because careful lautering isn't as important for ales.

            Lagers, on the other hand, are more naked and delicate. When brewing lagers, it's good not to use a mash-lauter combi-vessel (although some do get away with it), but to split a two vessel brewhouse up differently, i.e. with a mash tun/wort kettle and a separate lauter tun. This allows for a stepped mash and more careful lautering. (For a lager, decoction is not really important, but hitting the right temperatures is.) By more careful lautering, I mean less stress on the bed, better filtration and less hot-side aeration, so that the more "rough" flavors are avoided. Dedicated lauter tuns are also partially responsible for the higher yield in lager (continental) breweries, but for small brewers this isn't much of an issue.
            Last edited by crassbrauer; 07-30-2007, 01:36 PM. Reason: forgot something

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            • #7
              Adjustable cutting rakes

              Thanks for your input so far. This filter bed issue is starting to rule my life

              What impact does a lauter tun with height adjustable cutting rakes have on the filter bed thickness and what elevation should the rakes be at (absolute or as a percentage of the filter bed thickness?

              Any ideas or experiences?

              BelgianBrewer
              Last edited by BelgianBrewer; 04-05-2008, 01:10 AM.

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              • #8
                The knives should never go below a height a few inches above the false bottom. (Obviously, as you're adjusting the height, they should be turning.) During and immediately after cutting, the run-off should be recirculated until clear. Good luck.

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                • #9
                  The bed depth can be higher because careful lautering isn't as important for ales.

                  B****** Sorry, but it is. You are still looking to maximise extract by careful lautering. The key factor to bed depth is how, as previously stated, you treat the mash. If you use a two or more vessel system, i.e. mash in one vessel and transfer to the wort extraction vessel, then the mixing and temperature rises remove all the air out of the mash. Bed depths tend to be thinner for two reasons. Traditionally the malts were less well modified, i.e. less of the grain cell walls had been broken down and fewer amylolytic enzyme produced during malting, and retained in the malt after kilning. The grain had to be smashed up more finely to allow easier access for water, to allow it to penetrate, and re-activate the proteolytic enzymes and then the amylolytic enzymes. No if the grain has been smashed up, the bed will be less porous. So presumable as with all these things, it was realised that better extract precentages couldbe obtained by having a thiiner bed, and raking if the runoff became slow due to the bed setting in certian areas. Raking was required to maintain bed porosity.

                  The traditional British malt was well modified, which meant it normally had a higher colour due to sugars produced during malting. But this meant it did not have to be broken up as much, and the way it was mashed in, and then run off in the same vessel, menat that air was entrained in the mash, helping it to float. Because it was coarse, there was less resistance. The higher grain depth helped to improve extract efficiency (or perhaps it was just it didn't affect it as much)

                  I do agree about the stronger malt flavours hiding oxidation effects on malt, though I am sure I have seen somewhere that highly modified malts, particularly coloured malts are less prone to obvious oxidation flavours - sorry I can't remember when & where - possibly just a verbal comment from someone.

                  Whether it is ale of lager, you still use circa 76 C water for sparging

                  I don't agreee with recircualtion after deep bed raking. If you do that part way through sparge / runoff, you will get a layer of higher strength wort above wek worts / water, and will be forced to lose some extract. If your rakes are above the bottom of the bed, then there should be no need for recirculation.

                  Rake depth is crudely proportion to differential pressure across the bed, i.e. the higher the DP (i.e. the closer to blinding), the lower the rakes.

                  Oh yes, one final minor point - the greater the bed loading, the longer the runoff time, whichever system you use, but with a tendency to lose extract on thin beds, and especially if pushing fast turnrounds of thick beds
                  dick

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                  • #10
                    Sorry, I've been traveling a lot, but I wanted to send a quick reply to you, Dick, about lautering in Britian and on the Continent, namely, Germany.

                    I don't really like comparing British and Middle European brewing, because it's like comparing apples and oranges. They need to remain distinct to keep their unique characters. As I think I've mentioned, some of my favorite beers are brewed in Britian (and in Belgium, France and North America, as well), and diversity is what keeps things interesting, so I wouldn't change a thing about any of them.

                    My point about a mash/lauter vessel is that lautering cannot be performed to the degree of efficiency and quality that it can with a dedicated lauter vessel. Yes, I understand that British brewers want the get all the extract they can out of their malt using the methods, processes and raw materials they have on hand.

                    Germans, however, are obsessed with all the processes involved in brewing and have been with extract since they could measure it, and frankly, have done as much as possible to ensure they get the most out of their malt. This encompasses the whole process up to lautering: starting with using only summer barley (less husk/protein, more endosperm) to malting methods for maximizing extract (not modifying as highly as British malts to reduce extract loss coupled with more intense mashing) and the invention of various types of milling (wet, conditioned, multi-roll, husk separation, etc.) to optimizing lauter vessels (the newest being the Pegasus from Steinecker).

                    Yes, the smaller breweries aren't on the cutting edge with their technology, but they still brew with this in mind. Almost all malt houses in Germany, however, are capable of delivering malt to these specifications. And yes, winter barley will be used to make some specialty malts (especially this year!).

                    By the way, recirculation after bed raking is performed to keep the amount of fatty acids in the wort at a minimum, which can cause later problems for German beers.

                    Anyway, I will be in London soon, and I look forward to hitting a few of my favorite pubs. Can you recommend any I might have overlooked?

                    Cheers,
                    Chris
                    Last edited by crassbrauer; 10-30-2007, 08:10 PM. Reason: can't spell

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                    • #11
                      Good points being made here. I like posted differences between English and German process. However my experience as of late has been a mash/lauter combi using a variable speed pump controlled by a PID. Dick made an import last statement "Oh yes, one final minor point - the greater the bed loading, the longer the runoff time" once compaction starts in the tun then run-off continues to decrease. Using the variable speed pump will help in controlling compaction.

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                      • #12
                        That's also why you should never let the liquid level sink below the grain bed and never open the valve too wide going to your grant. Your pump should actually not be pulling directly on the grain bed! It should be gravity fed to a grant then pumped out. Gravity is the strongest force that should ever be used to bring about the processes involved in lautering (unless you have a mash filter, but then it's not "lautering"). I know of large breweries who let their bed drain dry and then add the sparge water, in order to increase the number of times they can brew per day, but for craft brewers it makes no sense, especially those using a mash/lauter vessel, where the height causes even more compaction than with a dedicated lauter vessel. These large breweries also often practice trub filtration, as well, so they can take out some of what got through by letting the bed drain.
                        Last edited by crassbrauer; 10-31-2007, 06:29 AM. Reason: can't spell

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