# Continuous Mechanical Stirring Of Mash During Conversion And Sparging.



## Hogan (5/9/07)

I am currently in the process of putting my new MLT together. I has two motor driven stir arms and I will be using it for both temp step mashes (direct heat) and infusion mashes.

The purpose of this post is to receive feedback from those brewers who use a motor driven stirrer during their mash conversion and batch sparge processes. I have heard that some brewery’s use a continual stir through the whole of the process whereas other home brewers with mechanical stirrers only stir and rest. There seems to be a worry about tannin extraction but I have come across no evidence to support this where the mash is not put under duress. 

Is the term ‘rest’ to be taken at its literal meaning where no disturbance of the mash is occurring. If so why is this better than constant movement and why do some (or maybe all) brewery’s follow the continual stir procedure. 

Would not constant circulation of the mash allow an even temperature distribution as that which takes place in a HERMS.

The batch sparge is meant to wash the mash of converted sugars so I would think that continuous movement in that case would also assist the process rather than having it stirred, rested and then lautered.


Cheers, Hoges.


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## oldbugman (5/9/07)

Going hightech and still batch sparging?


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## domonsura (5/9/07)

I was actually wondering about ultrasonic agitation of the mash........just to throw a spanner in the works.......


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## AndrewQLD (5/9/07)

Hogan, there is a difference between recirculation and continuous stirring of the mash. As in the case of a herms system, the wort is continuously recirculated but not the mash/grains, so essentially the wort is constantly flowing past and through the grains. I have no knowledge of the mash stirring commercial systems you are talking about but it sounds to me with continual stirring of the grain bed at the temps a mash runs at might cause the mash to become doughy and hard to sparge through.

Yes, the constant stirring would give an even temp distribution, and yes "rest" implies no movement or increase in temps.

But as I said, I have no experience with the method you are talking about so I am open to learning. Looking forward to hearing more.

Cheers
Andrew


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## Thirsty Boy (5/9/07)

I know that a lot of commercial breweries do indeed stir throughout the mash process. As you guess, it allows consistent temps if they are adding heat for steps or to maintain temp... it also does the efficiency some good by making sure that all the grain is accessible to the enzyme containing liquid, no dry spots, no dough balls, no areas of higher or lower L:G ratio.
At work our mash is constantly stirred, usually between 9 & 15 RPM. Even during the "rests"

If you stir during your batch sparge however, you will lose the benefits of setting up a grainbed and the wort filtering that provides... the wort you run off would or could contain anything big enough to fit through the holes in your false bottom / manifold / Hose Braid / Filter screen / Filter Cloth.

That might not be so great... I'm not a believer that sparkling bright wort necessarily leads to beer thats any better... although I know that some people do, I don't think the proof is conclusive either way... However I don't think anyone out there is deliberately allowing "chunks" to get through; and stirring during your sparge may well do that.

Stirring your mash when you add sparge water is pretty standard for batch sparging (or at least I think it is ??) but equally standard would be to stop stirring and then do at least some sort of recirculation to set up a grain bed...

You could try using a filter cloth in your mash tun, maybe over the false bottom? Then depending on the pore size of the cloth, not a lot would get through and you would probably be fine. When I do BIAB batches - thats pretty much the result. A little more "fine" stuff than you would normally get in a standard lauter, but not a great deal. There is still a bit of a question whether that fine stuff is; or isn't going to effect the long term stability of BIAB brews though, so the same question would apply to a stirred mash tun with a filter cloth or screen.... A finer cloth/screen solves the problem, but slows down the lauter and maybe gets clogged up.

For the possible (and my guess is minor if any) increase in efficiency you might gain by stirring during the actual lauter, rather than stir, recirculate - then lauter - my gut feel is that it'd be heaps more trouble than it was worth.

But if you are dead set keen to do it, you could manage to rig a system to get around the issues.

Thirsty

PS... pictures of stirring set-up please, I have been thinking about doing it for giggles myself


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## MHB (5/9/07)

Hogan
Rest only refers to the temperature, a lot of commercial breweries stir all the time; this is because they are heating the sides and/or bottom of the "Mash Mixing Vessel" when they want to change the temperature.

As you said this gives an even distribution of heat when they want a step.

The main things to watch fore are that there are no dead spots - areas that dont get stirred.

And that the tips if the propeller arent moving over about 3m/s, faster causes cavitation and increases oxygen uptake (HAS).

Big blades around 85% of the diameter of the tun, moving relatively slowly are the best, oh and they should be close to the bottom.

MHB


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## Hogan (5/9/07)

Thirsty Boy said:


> I know that a lot of commercial breweries do indeed stir throughout the mash process. As you guess, it allows consistent temps if they are adding heat for steps or to maintain temp... it also does the efficiency some good by making sure that all the grain is accessible to the enzyme containing liquid, no dry spots, no dough balls, no areas of higher or lower L:G ratio.
> At work our mash is constantly stirred, usually between 9 & 15 RPM. Even during the "rests"
> 
> If you stir during your batch sparge however, you will lose the benefits of setting up a grainbed and the wort filtering that provides... the wort you run off would or could contain anything big enough to fit through the holes in your false bottom / manifold / Hose Braid / Filter screen / Filter Cloth.
> ...



All good points Thirsty and the majority coincide with my thinking. I currently batch sparge using the infuse, stir, rest, stir, lauter method and it has given me 85% pre-boil efficiency up to now, so no complaints there. Just looking to open new ground and feel that a grain bed filter for batch sparging may not be all its cracked up to be <_< considering the recent views on cloudiness and even some chunky bits in the boil not being the negatives they were once thought to be. This of course is different in the case of fly sparging where a grain bed is a necessary but also a lot more time consuming. I have some thoughts on how to ensure I get the full measure from my new mash tun without injecting too many grainy bits. My tun is in fabrication stage at this time and I will provide pics when it is set up.

Cheers, Hoges.


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## Hogan (5/9/07)

MHB said:


> Hogan
> Rest only refers to the temperature, a lot of commercial breweries stir all the time; this is because they are heating the sides and/or bottom of the "Mash Mixing Vessel" when they want to change the temperature.
> 
> 
> MHB




So MHB - the brewery's are stirring all the time when they are changing step temperature during conversion. But are they stirring during the whole of the batch sparge? I feel we may be worrying unnecessarily about grain bed filtration especially if you have a manifold capable of fine filtering.

My set-up will follow your recommendations. I have a motor turning at 15 rpm with torque that will hold a bull out of the urinal. Blades rotating close to the bottom, inside the 25mm s/s braid and a second blade above that.


Cheers, Hoges.


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## Jazzafish (5/9/07)

Just started working in a brewery, so a little new to the subject. However during a mash I asked the brewmaster a couple of questions and the answers are below.

Basically the mash is constantly stirred at my work, for reasons mentioned already... However during the lauter and sparge we have the facility to stirr/rake, but don't. After asking why I was told that it wasn't nessesary for most brews, can help if your mash is sticky - from using a bit of wheat malt- But generally the system gave little difference with or without the rake running. I say rake as the brewmater used that term and the blade is like a rake in the lauter tun. The mash tun is more paddle like.

One observation is that the Luater Tuns rake sat higher up in the grain bed, and by the look of it doesn't move the grain in the same manner as the mash tun... which is more fan like in shape and sits on the bottom of the vessel.

Another point was a percent or two efficiency is not worth the hassel when you consider that longer sparges eat into following batches time. 

Sparging aside, and maybe O/T but the biggest factor in the efficiency came down to the malt quality and the milling... all factors of the conversions/extractions are dependent on the grain and crush quality.


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## Thirsty Boy (6/9/07)

As you say Jazza,

Raking is quite different to "stirring" and its main purposes are to stop channeling in a continuous sparge grain bed, and too help improve run-off rate in a sticky/stuck mash.

The rakes are usually much more like vertical knives, and they cut the grain bed rather than churn it around. They are able (well they are in our system) to be raised or lowered in order to cut to a greater or lesser depth through the bed, but they would pretty much not go to the bottom, thus they dont greatly disturb the last few inches which is where the lions share of the grain bed filtering action is taking place.

On a homebrew scale, you can achieve pretty much the same thing by literally cutting your grain bed with a kitchen knife. A few cuts through the bed with tip of the blade an inch or two short of the bottom, in a nice "diamond pattern" is I believe a quite effective way of unsticking a mash and breaking up channeling. But I'm not a regular fly sparger at home so I aint no expert and I could well be wrong.

Anyway, it sounds like Hogan is getting all radical on our asses and has decided to buck the traditional brewing wisdom. I hope it works. I just keep gaining more and more respect for how robust the brewing process actually is... there are so many ways to skin this particular cat and still make great beer, that nothing would surprise me anymore.

Cheers

TB


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## /// (6/9/07)

From seeing someof these systems, I'd vote for a wide and thin grain bed compared to a deeper infusion mash. Also I am wondering about your mill gap and resultant crush size. So, with all this stiring (and possibly pumping) what are you trying to acheive?

Scotty


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## The King of Spain (6/9/07)

AndrewQLD said:


> I have no knowledge of the mash stirring commercial systems you are talking about but it sounds to me with continual stirring of the grain bed at the temps a mash runs at might cause the mash to become doughy and hard to sparge through.
> 
> Cheers
> Andrew



I did a mini mash once, and with the smaller grain bill decided to experimented with direct heating and constant stiring. It was impossible to sparge from the start. I ended up using a big grain bag to..... You get the idea, a disarster.

Cheers


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## Hogan (6/9/07)

AndrewQLD said:


> Hogan, there is a difference between recirculation and continuous stirring of the mash. As in the case of a herms system, the wort is continuously recirculated but not the mash/grains, so essentially the wort is constantly flowing past and through the grains.
> 
> Cheers
> Andrew



Yes of course you are right there Andrew. There is a very big difference between HERMS and stirring with no grains going through the recirculation. My mistake.


Cheers, Hoges.


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## Hogan (6/9/07)

Jazzafish said:


> Just started working in a brewery, so a little new to the subject. However during a mash I asked the brewmaster a couple of questions and the answers are below.
> 
> Basically the mash is constantly stirred at my work, for reasons mentioned already... However during the lauter and sparge we have the facility to stirr/rake, but don't. After asking why I was told that it wasn't nessesary for most brews, can help if your mash is sticky - from using a bit of wheat malt- But generally the system gave little difference with or without the rake running. I say rake as the brewmater used that term and the blade is like a rake in the lauter tun. The mash tun is more paddle like.
> 
> ...




Thanks Jazza. Seems there is consensus on the continuous stirring of the mash during conversion followed by the resting of the grain bed during the sparge period. I have had no trouble with my grain crush in the past and as stated have achieved excellent efficiency in my old system. The cutting method would not be conducive to my new systems setup and I most likely stick to my tried and tested sparge method. 

Cheers, Hoges.


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## Hogan (6/9/07)

Thirsty Boy said:


> Anyway, it sounds like Hogan is getting all radical on our asses and has decided to buck the traditional brewing wisdom. I hope it works. I just keep gaining more and more respect for how robust the brewing process actually is... there are so many ways to skin this particular cat and still make great beer, that nothing would surprise me anymore.
> 
> Cheers
> 
> TB




Hi Thirsty - I feel its more about evolution of the traditional brewing methods but, 'bucking the system' is a close context. We all know that BIAB and the 'No Chiller Method' flew in the face of conventional brewing techniques and they have been shown to work notwithstanding much opposition to attempts at changing the brewing statusquo. I'm all for looking for more efficient and effective ways of making great beer and that is the reason I put forward an alternative method and see if it flys. Thanks for your input TB.


Cheers, Hoges.


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## /// (6/9/07)

Are we confusing equipment here. There are fundemental differences and applications between a mash mixer, lauter tun and infusion mash tun. 

The 50hl mash mixer at AIB has the paddles where you would stir then the mash is pumped to the lauter tun for sparging.

Scotty


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## sinkas (6/9/07)

I Know our german member Zwickle uses a mash stirrer, maybe he could give some insight.


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## Hogan (6/9/07)

/// said:


> Are we confusing equipment here. There are fundemental differences and applications between a mash mixer, lauter tun and infusion mash tun.
> 
> The 50hl mash mixer at AIB has the paddles where you would stir then the mash is pumped to the lauter tun for sparging.
> 
> Scotty




No equipment confusion here Scotty  but then again I am talking domestic not commercial. I will be stirring, direct heat temp stepping, mashing out, infusing, sparging and lautering through a manifold - all in the one container. 

Zwickel has been kind enough to help me through my planning stage. 


Cheers, Hoges.


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## Jazzafish (8/9/07)

> Thanks Jazza. Seems there is consensus on the continuous stirring of the mash during conversion followed by the resting of the grain bed during the sparge period. I have had no trouble with my grain crush in the past and as stated have achieved excellent efficiency in my old system. The cutting method would not be conducive to my new systems setup and I most likely stick to my tried and tested sparge method.
> 
> Cheers, Hoges.



Good stuff mate,

Good luck with your All in One Tun! 

If you wanted to go over the top, you could have a detachable stir shafts! Attach one to stir the bottom of the mash... remove and insert a rake style for the lauter/sparge! h34r:


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## Hogan (8/9/07)

Jazzafish said:


> Good stuff mate,
> 
> Good luck with your All in One Tun!
> 
> If you wanted to go over the top, you could have a detachable stir shafts! Attach one to stir the bottom of the mash... remove and insert a rake style for the lauter/sparge! h34r:



Great idea Jazza. All I'd have to do is plant a few Bonsai trees and I could have my own Japanese garden :super: 


Cheers, Hoges.


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## deckedoutdaz (8/9/07)

I thought Zwickel only called me Grasshopper, maybe in 12 months there will be a dozen ninja beer brewers with Zwickel's avatar burnt onto the insides of our forearms....


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## Thirsty Boy (9/9/07)

Jazzafish said:


> Good stuff mate,
> 
> Good luck with your All in One Tun!
> 
> If you wanted to go over the top, you could have a detachable stir shafts! Attach one to stir the bottom of the mash... remove and insert a rake style for the lauter/sparge! h34r:




ooooh, I *like* that idea


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## fraser_john (9/9/07)

Thirsty Boy said:


> ooooh, I *like* that idea



I am planning mine and will be using shaft collars to attach the paddles/rake to, use an allen key, they can be moved up/down the shaft on demand, so I can alter the grain bed depth and where the paddles sit in the bed.


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## peter.b (25/9/07)

After a tour recently of a micro brewery on the gold coast, the mash mixing vessel, has a large stirrer built in to the vessel, approx 80-90% of the diameter. We were informed it only rotates very slowly. About 1 rpm. Also the blades rotate to push the mash down, not up, as i would have expected. This tends to push the mash into the bottom and up the sides. Sounds good in theory! Hope this doesn't cause any more head scratching.


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## Jye (25/9/07)

Here it is for those that are interested.


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