HERMS brewing process - Mash in and stiring

[Muz]

I've recently switched to a HERMS system and, while I've only done two brews on it, I'm loving it already.

I realise though that there are a lot of different ways to use a system like this and I'm keen to understand how people a) mash in and b) how and when they stir when HERMS brewing.

My first brew I underlet to mash in and didn't stir at all (assuming recirc would make stirring redundant). My efficiency on this brew was rubbish. And while I don't care too much about efficiency I want it somewhere in the 70s at least.

My second brew I also underlet and stirred a few times in the first 30 mins of the mash. Things weren't much better.

I read something on the internet (so it must be right) about people stirring when they sparge. This seems to defeat the purpose of setting the grain bed to me. So, I thought I would ask how others are doing this.

Cheers.

 

[S.E]

I read something on the internet (so it must be right) about people stirring when they sparge. This seems to defeat the purpose of setting the grain bed to me. So, I thought I would ask how others are doing this.

I usually, or at least when I remember to stir the top few inches or 60cm-90cm of the mash when fly sparging and find it improves efficiency. So long as you are not disturbing the bottom ¾ or so you should be fine and will help avoid channeling down the sides of the mash tun.

 

[Muz]

I often, or at least when I remember to stir the top few inches or 60cm-90cm of the mash when fly sparging and find it usually improves efficiency. So long as you are not disturbing the bottom ¾ or so you should be fine and will help avoid channeling down the sides of the mash tun.

huh, that's really interesting. Do you stir any other time? Like during to rest?

 

[S.E]

huh, that's really interesting. Do you stir any other time? Like during to rest?

Just at mash in then when sparging. When sparging I will give a stir one or a few times if I remember or can be bothered. Just to stir up the fine particles on top and improve flow through the grain. Some commercial breweries have rakes at the top of the MT to do the same.

 

[MHB]

Hey Muz, I know you have been around for a while, but others might read this so start with the basics, get everyone on the same page.

First up; All recirculating systems have pretty much the same requirements to work properly.

The crush is critical, your grain bed needs to be very free draining so you need a coarser grind than you would with BIAB or even a conventional 3V system. If the wort can’t flow through the grain bed evenly you will get very spotty results with some parts of the grain getting too much rinsing and some getting none.
At the end of the mash it’s a good idea to turn out the grain, should be like a big soggy scone, dissect it and have a look, is it all evenly coloured, is the consistency even, taste a bit of grain from a couple of spots. If some is sweet and some just straw you have uneven flow, check for dough balls.

What works for me is to mash in, stir enough to get the grain evenly distributed and to make sure there are no dough balls, then leave it the hell alone. I do get efficiencies in the low to mid eighties as a matter of course.

Another fairly common problem with many home made systems is that they are over powered. If the heating surfaces (elements, copper pipes, side walls...) are too hot you can denature all the enzymes as the wort flows over the heating surface, as you are recirculating many times the wort volume over an hour or so you can end up with no functional enzymes.
Worth having a very careful look at heating surfaces, shouldn’t be so much of a problem on a commercially made system, but even they are not all created equal.

Stirring the sparge? Hum, well I wouldn’t with the possible exception of a batch sparged mash in a 3V, then you need to reset the bed (establish the beds ability to filter out fines) by recirculating it back to the condition ir was in before you stirred it. Sort of gets a bit circular, but stirring a batch sparge wasn’t uncommon back in the parti-gyle days. Not really something I would be looking to do in most cases.

Hope that helps if you can’t see what’s going wrong a bit more info will help diagnose the problem.
Mark

 

[S.E]

The crush is critical, your grain bed needs to be very free draining so you need a coarser grind than you would with BIAB or even a conventional 3V system. If the wort can’t flow through the grain bed evenly you will get very spotty results with some parts of the grain getting too much rinsing and some getting none.

This is a good point and I should also have mentioned that when I was able to achieve a good grind and floating mash I never needed or bothered to stir the top of the mash.

However my Mash Master Mill is getting on a bit now and doesn’t give the perfect crush it once did when new. So if you cannot achieve a perfect crush with your mill then try stirring the top of the grain bed. This is what the rakes on mash tuns were designed to do. I find stirring can lift efficiency from around 70% to 80%-85% on my system.

 

[MHB]

The dreaded grey draff, that’s the name given to that fine grey past layer that can build up on top of the grain bed and block all flow.
The smaller the diameter (mostly) of the rollers the more explosive is the crushing action, more fines more draff.
Speed of rotation, surface texture... all play a role but its mostly the diameter. Hence the old saying in brewing "the bigger the rollers the better the crush".
Knifing the top layer is a pretty common counter, no need to go too deep, just some cross cuts through the draff so the wort can flow again. Ideally without too much crud coming out the bottom and into the kettle.
Top end commercial lauters have turbidity meters on the outlet and they can automatically adjust the rake depth and rotation based on both flow and turbidity (and more parameters). This is part of why the best (biggest) commercial breweries can get near theoretical (100%) yields. Some of the modern filter presses are getting more than 100%, something like 106% has been done.
Before anyone jumps up and down, that a better yield than a congress mash test done with distilled water and defined temperature steps, water to grain ratio (L:G ~8:1), no pH adjustments... all of which might not be the best way to get extract out of malt.
Mark

 

[S.E]

The dreaded grey draff, that’s the name given to that fine grey past layer that can build up on top of the grain bed and block all flow.
The smaller the diameter (mostly) of the rollers the more explosive is the crushing action, more fines more draff.
Speed of rotation, surface texture... all play a role but its mostly the diameter. Hence the old saying in brewing "the bigger the rollers the better the crush".
Knifing the top layer is a pretty common counter, no need to go too deep, just some cross cuts through the draff so the wort can flow again. Ideally without too much crud coming out the bottom and into the kettle.
Top end commercial lauters have turbidity meters on the outlet and they can automatically adjust the rake depth and rotation based on both flow and turbidity (and more parameters). This is part of why the best (biggest) commercial breweries can get near theoretical (100%) yields. Some of the modern filter presses are getting more than 100%, something like 106% has been done.
Before anyone jumps up and down, that a better yield than a congress mash test done with distilled water and defined temperature steps, water to grain ratio (L:G ~8:1), no pH adjustments... all of which might not be the best way to get extract out of malt.
Mark

Ok, so thanks for all that extra and possibly confusing info Mark? But are we advising Muz that stirring the top layer of the mash is ok or not?

 

[MHB]

I wouldn’t!
One reason to recirculate is to filter the wort, because in a constantly recirculating system we need to have a very permeable bed that is much worse at trapping fines (but it has an hour or so to get it right), if you stir the fines up they will elute out to the kettle or sink to the bottom of the tun in a 1V system. Either way you are undooing the filtering that was established over the hour or so that the mash was running.
Just running a couple of knife cuts across the surface will let the wort through and leave most of the draff undisturbed. You keep a nice clear wort and the flows you want.

I'm sure you meant 60-90mm not cm in your first post, even that is deeper and more likely to cause problems than I would go. Literally cross cut the surface with a knife, you only need to get through the grey sludge so maybe 10-12mm (half an inch or so in the old money), Muz hasn’t mentioned any problems with draff building up enough to block flow, anyone who is and is using a recirculating mash system probably need to think about a better milling option
Mark

 

[Half-baked]

Muz, are you sure it’s not your sparge? Whenever I’ve had poor efficiency using the 3v set-up, I’m pretty sure it’s because I rushed the sparge…

 

[newers]

Muz, are you sure it’s not your sparge? Whenever I’ve had poor efficiency using the 3v set-up, I’m pretty sure it’s because I rushed the sparge…

Agree with this - although I batch sparge with my 3V (not sure why... just do), I drain the initial batch very slowly into the boil vessel (like over 30 mins), then do the same for the sparge (another 30 mins to drain). Efficiency moved from mid 60's/low 70's to high 70's/mid 80's when I started taking my time.

Off topic - but time for me to start fly sparging after reading all of this!

 

[Vic]

Hey Muz, I know you have been around for a while, but others might read this so start with the basics, get everyone on the same page.

First up; All recirculating systems have pretty much the same requirements to work properly.

The crush is critical, your grain bed needs to be very free draining so you need a coarser grind than you would with BIAB or even a conventional 3V system. If the wort can’t flow through the grain bed evenly you will get very spotty results with some parts of the grain getting too much rinsing and some getting none.
At the end of the mash it’s a good idea to turn out the grain, should be like a big soggy scone, dissect it and have a look, is it all evenly coloured, is the consistency even, taste a bit of grain from a couple of spots. If some is sweet and some just straw you have uneven flow, check for dough balls.

What works for me is to mash in, stir enough to get the grain evenly distributed and to make sure there are no dough balls, then leave it the hell alone. I do get efficiencies in the low to mid eighties as a matter of course.

Another fairly common problem with many home made systems is that they are over powered. If the heating surfaces (elements, copper pipes, side walls...) are too hot you can denature all the enzymes as the wort flows over the heating surface, as you are recirculating many times the wort volume over an hour or so you can end up with no functional enzymes.
Worth having a very careful look at heating surfaces, shouldn’t be so much of a problem on a commercially made system, but even they are not all created equal.

Stirring the sparge? Hum, well I wouldn’t with the possible exception of a batch sparged mash in a 3V, then you need to reset the bed (establish the beds ability to filter out fines) by recirculating it back to the condition ir was in before you stirred it. Sort of gets a bit circular, but stirring a batch sparge wasn’t uncommon back in the parti-gyle days. Not really something I would be looking to do in most cases.

Hope that helps if you can’t see what’s going wrong a bit more info will help diagnose the problem.
Mark

If the heating surfaces (elements, copper pipes, side walls...) are too hot you can denature all the enzymes as the wort flows over the heating surface, ??
You got me confused, this is a HERMS system, wort should never flow over heating elements as it does on direct heat 1V, 3V and RIMS system. Reducing heating power can help even out the overall mash temperature but increase ramp times. The HERMS return will always be hotter than the middle or lower part of the mash. Stir the mash once after underlet mash in then stir the top 1/3 every 15 min or so, not critical.

 

[S.E]

I wouldn’t!
One reason to recirculate is to filter the wort, because in a constantly recirculating system we need to have a very permeable bed that is much worse at trapping fines (but it has an hour or so to get it right), if you stir the fines up they will elute out to the kettle or sink to the bottom of the tun in a 1V system. Either way you are undooing the filtering that was established over the hour or so that the mash was running.
Just running a couple of knife cuts across the surface will let the wort through and leave most of the draff undisturbed. You keep a nice clear wort and the flows you want.

I'm sure you meant 60-90mm not cm in your first post, even that is deeper and more likely to cause problems than I would go. Literally cross cut the surface with a knife, you only need to get through the grey sludge so maybe 10-12mm (half an inch or so in the old money), Muz hasn’t mentioned any problems with draff building up enough to block flow, anyone who is and is using a recirculating mash system probably need to think about a better milling option
Mark

Ok I think I see the confusion here Mark. I was not talking about a constantly recirculating system. I quoted and was specifically responding to the question about stirring the mash during sparging.

I did mean 60-90mm not cm in my first post but I did not actually state the depth of the grain bed and went on to say “So long as you are not disturbing the bottom ¾ or so” (of the mash) so hopfully this will be clear enough for most folk reading it.

If I correctly understand the post from Vic above he stirs the top 1/3 of the mash every 15 min or so with a HERMS system?

 

[S.E]

you need a coarser grind than you would with BIAB

I have seen this little nugget of misinformation that grain for BIAB needs to be milled fine being regurgitated for years on here. I believe it stems from the pseudoscientific experiments carried out here on AHB in the early days when BIAB started becoming popular again and some members were looking for a simpler method of brewing than 3V.

I’m not sure exactly why the fine crush for BIAB was arrived at or thought to be necessary but if used properly a grain bag is similar to a false bottom and a good coarse crush will give great results.

 

[mynameisrodney]

I don't think its a case of people saying you need to do a fine crush. They are saying you can do a fine crush without negative impacts, whereas with other systems you can't.

 

[contrarian]

Another factor might be the liquor to grain ratio in your mash tun while recirculating. I find that if it is possible to have a couple of inches of fluid sitting on top of the grain bed that this helps with the recirculation process. If you are returning wort into the grain bed you are much more likely to have issues with channelling and a greater need to stir.

 

[Muz]

Thanks all for your advice. I've found this thread really helpful.

As I mentioned, my HERMS set up is pretty new and I've only done a couple of brews with it. Both had brewhouse efficiencies in the 60s and that just didn't seem right. While I've seen and read heaps about building HERMS systems there doesn't seem to be a lot out there about how best to use it.

I've been able to determine a couple of things I'm doing wrong:

1) I was recirculating really slowly. For some reason I thought this was the way to do it. I probably got mixed up with sparging slowly. Anyway, it looks like most people open the values up 100% for the mash recirc. I'm sure this will make a huge difference

2) While I sparged to maintain about 5cm of sparge water on top of the grain bed at all times I did sparge really quickly both times. I've now read most people recommend sparging over 45-90 mins. I'm sure this will make a difference too.

3) I would describe my grain crush as medium. I actually don't have a mill yet (next thing to save up for) so I'm just getting Grain and Grape to crush it for me. I'm going to start adding 250-500g of rice hulls to each brew depending on if I've got wheat or oats in the grist.

4) I plan to continue underletting and then stir through the first 30 mins of the mash. I'll then let things set. I might rake the top of the grain bed when I start my sparge as well and see how that goes.

I think my issues are mainly 1 and 2.

Thanks again everyone for your help.

 

[Tony121]

Have to ask as not specifically stated in your description, are you letting the grain bed set before recirculating?

 

[Muz]

So I underlet, stir, give it 5 mins for the temp to settle then start recirculating. I've seen people mash in while recirculating though. Does that make a difference?

 

[Tony121]

Do you start recirculating slowly then ramp up or go straight for your intended flow?
I’ve found the best way to ensure good even flow is to mash in, stir, let sit for 10-15 mins then start recirculating at very low flow slowly increasing over 5-10mins until I’m at the flow I want. I then don’t touch at all from there on.
May or may not be an issue for you, just giving you my experience.