# Mash Thickness - Biab



## ArcLight (10/10/12)

How thick is your mash when brewing in a bag (BIAB)?

How thin is too thin?
I would think that this is more of a problem if your grain bill contains a large percentage of gains with no diastatic power (such as flaked wheat).

BIAB is mashed thinner than traditional all grain mashes, but its still probably 6 Liters : Kilo.

When do you see a drop off in efficiency?


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## beerdrinkingbob (10/10/12)

I run at 4.5 ltrs/kg, place the bag in a bucket to drain and poor 8 ltrs of hot water over it (to get my volumes and extra sugar) and get 70% in the fermenter. That scenario is 9 kg of grain in a 50 ltr keggle, making 31 ltrs of high gravity wort, once diluted 40 ltrs of 1.050

Key to good BIAB efficiency is a really good stir on the way up to and at mash out temps IMO.


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## ArcLight (10/10/12)

beerdrinkingbob said:


> Key to good BIAB efficiency is a really good stir on the way up to and at mash out temps IMO.



How often do you sir the mash?
I stir it in well. 
Then mostly leave it alone, unless the temperature drops, when I add a touch of heat, and re stir.

I'm not so interested in the sparge, as the actual mash thickness (liquor to grain ratio)


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## geneabovill (10/10/12)

I go 7.5lpk & got 81% mash efficiency, according to Beersmith. No sparge, and let the bag drain over the kettle during ramp up to boil.


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## Crusty (10/10/12)

ArcLight said:


> How thick is your mash when brewing in a bag (BIAB)?
> 
> How thin is too thin?
> I would think that this is more of a problem if your grain bill contains a large percentage of gains with no diastatic power (such as flaked wheat).
> ...



It depends on your grain bill.
I use BrewMate which will do the calculations for you.
I set my grain absorption rate to 0.60l/kg & my targets are spot on.


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## Mike L'Itorus (10/10/12)

read this

iirc, discussed ad nauseam in the dedicated biab thread. Several years ago.


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## ArcLight (10/10/12)

[quote name='Mike L'Itorus' post='961117' date='Oct 10 2012, 07:50 AM']read this

iirc, discussed ad nauseam in the dedicated biab thread. Several years ago.[/quote]

This is a great article and I have read it several times, including before I posted. I have also discussed it with the author.
In his experiments he doesn't mash very thin though. He tests 5L/K, which is roughly 2 quarts/pound.

I am wondering about 3:1? 4:1? beyond?

At some point the enzymes are diluted. Maybe thats ok, but conversion is slower and you really do need 90 minutes, and must not exceed 65C, else the B-Amylase will denature.

What I am thinking to to hold back some of the extra water, rather than mash "very thin" (> 6L/K), and perform a dunk sparge. Stirring up the grains and making sure there is good circulation, with 6+ liters of liquor.

For the first time ever using BIAB I didnt get good results with a L:G ratio of 34 Q : 10 lbs of grain. I had meant to hold back some water for the sparge and forgot, instead I just mashed thin. Even with squeezing the bag hard, I didn't get 70% into the fermentor (though it was close). Maybe the crush was not optimal, and this is just an outlier. 

I don't think people usually mash that thin, counting only the grains with diastatic power.

At some point I will conduct an experiment and compare thicknesses of 2:1, 3:1, 4:1 at 65C and at 68C


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## katzke (11/10/12)

ArcLight said:


> For the first time ever using BIAB I didnt get good results with a L:G ratio of 34 Q : 10 lbs of grain. I had meant to hold back some water for the sparge and forgot, instead I just mashed thin. Even with squeezing the bag hard, I didn't get 70% into the fermentor (though it was close). Maybe the crush was not optimal, and this is just an outlier.
> 
> I don't think people usually mash that thin, counting only the grains with diastatic power.



It is not your water to grain that is causing problems. It is something else. I have done 11 pounds with 6 of that flaked wheat and oats in just over 8 gallons. Came to within 2 points of calculated.


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## ArcLight (11/10/12)

katzke said:


> It is not your water to grain that is causing problems. It is something else. I have done 11 pounds with 6 of that flaked wheat and oats in just over 8 gallons. Came to within 2 points of calculated.



Katzke,
How long did you mash for, and at what temperature?
Thats > a 6-1 ratio (32Q : 5G). 
Its encouraging that that thin a mash works so well.


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## Thirsty Boy (11/10/12)

Your problem is that your expectations are too high.

You "didn't get 70% into the fermenter" - and for a first time BIAB brewer I wouldn't expect you would. Mind you, I wouldn't expect it if you were batch sparging either.

BIAB mashes convert perfecly well, without particularly great effect on either conversion time or wort fermentability, at up to and including L:G ratios of more than 8:1 (litre per kg, not your silly pounds and quarts). I might not try mashing any great amount of adjunct at higher than 8:1... but it'd probably work anyway.

Given that a "normal" sort of beer at say about 5% abv is going to mean about 5kg of grain in about 35L of water... a mid range BIAB L:G ratio is around 7:1 - At this ratio, I'd be expecting a combined mash/lauter efficiency (ie measured in your kettle) of somewhere in the mid 70's. What that translates to "in the fermenter" I have no idea, because I dont know how fussy you are about trub separation, how much you lose to your plate chiller, how much you leave behind in your no chill cube, how much you spill on the floor... or any of the other things that make efficiency measured in the fermenter a completely useless thing to consider when you are talking to anyone who isn't actually standing in your brewery with you.

As your desired ABV goes down, your grain bill will go down and your L:G ratio will increase - and so will your efficiency as the effect of not sparging is mitigated. If you were brewing an Ordinary Bitter, I'd expect you to be looking at a M/L efficieny around the 80% area. And of course the opposite is true, as your desired ABV increases, your L:G ratio decreases and contrary to your probable expectations, your efficiency will drop, quite markedly. Enough so that I would generally suggest that if you are planning a beer much more than 6% abv, its probably worth considering a Dunk Sparge for that beer. Depending on the size of your pot, you may have no choice anyway.

As a rule of thumb - BIAB mashed with the full volume of water required, performs just about as well as batch sparging the same recipe would work. BIAB usually gets a slightly better M/L efficiency than batch sparging (there are a number of reasons why), but you end up sacrificing more wort to kettle trub, so it evens out on the way to the fermenter.

Differences you experience to those "rough" parameters - are due to your technique, your equipment, your grain, your crush, your experience, your skill - not I'm afraid, to any inherrent inability of the BIAB process to convert starch to sugar and get it in the pot.

TB


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## yum beer (11/10/12)

Thirsty, thats a hell of a reply for 4 in the morning.


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## bignath (11/10/12)

Thirsty Boy said:


> Your problem is that your expectations are too high.
> 
> You "didn't get 70% into the fermenter" - and for a first time BIAB brewer I wouldn't expect you would. Mind you, I wouldn't expect it if you were batch sparging either.
> 
> ...



Thirsty, that's a bloody fantastic post mate!

I've been confused about efficiency (mash vs brewhouse or "in the fermenter") for ages, and what they mean, and how they relate or don't relate.

Thanks for summing it up so clearly, and as noted above, at a spastic time of day too.

Cheers mate,

Nath


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## Bribie G (11/10/12)

A bit off topic but my understanding from "Braukaiser" is that most modern German breweries do stepped infusion mashes such as the Hochkurz mash. Rather than ramping up the temperature by directly heating the wort (as in HERMS or BIAB in an urn) they start with a thick mash then just add a set amount of boiling water to the mash to raise the temperature and would therefore be diluting the mash at each stage. 

I've often thought about doing that myself to extend the life of the urn and avoid build up of gunk on the element, not to mention a quicker ramp-up especially on the way up to mashout. I must give it a go sometime. There are some good liquid mixing calculators online so not rocket science.


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## hazard (11/10/12)

Bribie G said:


> A bit off topic but my understanding from "Braukaiser" is that most modern German breweries do stepped infusion mashes such as the Hochkurz mash. Rather than ramping up the temperature by directly heating the wort (as in HERMS or BIAB in an urn) they start with a thick mash then just add a set amount of boiling water to the mash to raise the temperature and would therefore be diluting the mash at each stage.
> 
> I've often thought about doing that myself to extend the life of the urn and avoid build up of gunk on the element, not to mention a quicker ramp-up especially on the way up to mashout. I must give it a go sometime. There are some good liquid mixing calculators online so not rocket science.


I've not done a german style beer, but i do something similar for my dry stouts which are 20% flaked barley. I do a thick mash in at 50 deg (around 2L/kg) then add a few litres of boiling water to raise temp to 65 deg for 30min, to reach a target ratio of approx 2.5L per kg. BrewSmith works out all the volumes for me. I use a 27L rubbermaid cooler, and batch sparge. I'm too lazy to do a proper mash out, but with this approach I've not had a stuck sparge (had a terrible stuck sparge previously when I used a single infusion mash at 65deg, and didn't mash out).


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## Thirsty Boy (11/10/12)

Nothing wrong with stepped infusions - just another way to get heat into the pot. Neither better, nor worse - just different. Not much good to you though if you are trying to maintain your brewery at the lovely simple and easy to maintain number of vessels that BIAB actually requires .... one.

You can step infuse if you want - of course you can, wont hurt, will work - perfectly. But.... you don't in any way shape or form, need to do it for either normal or step mashing with BIAB because of the L:G ratios.


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## ArcLight (12/10/12)

ThirstyBoy,
I don't think my expectations are too high because previously doing stovetop BIAB I was always hitting 70%+ into th3 ferementor. I use a hops bag, so there is little hops residue flowing in, nor flour, as I pour grain into the bag away from the pot. There will always be some trub, but thats true of All Grain in general. I suppose you could measure what comes out of your cube before pitching the yeast if you wanted, but I don't think most people measure efficiency that way, as you need the wort to cool and settle. Efficiency into the fermentor is a commonly used method.

In the past I had always sparged. I didnt since the mash was so thin. I think that makes a difference.

At some point I will have to conduct a real experiment at different L:G ratios to see if there is a point at which the mash thinness reduces efficiency. Maybe thinner, lower temperature mashes just take longer, so I should stir it up occasionally and mash longer.


>>Given that a "normal" sort of beer at say about 5% abv is going to mean about 5kg of grain in about 35L of water... a mid range BIAB L:G ratio is around 7:1 -

Why so much water? How mush is lost to boil off? 4-5 liters? How much lost to grain absorption and hops absorption? 3 liters? I squeeze the hops bag so loose almost nothing. Call it 9 extra liters needed.
20L + 9L = 29L needed , not 35.


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## katzke (12/10/12)

ArcLight said:


> ....Maybe thinner, lower temperature mashes just take longer, so I should stir it up occasionally and mash longer.
> 
> 
> 
> ...



In my experience you will be short if you want 5 gallons of finished beer. If you want only 5 gallons in the fermentor then you will be about there. You are loosing more in the bag then you think. Plus when you use things like oats or raw wheat that hold water you will see a difference.

Also why the comment on low mash temp? You need to mash at the correct temp. Will not or should not be much difference between brew styles for mashing. Not enough to make any difference in conversion.

I raised my efficiency numbers by getting a good thermometer, and playing with water. The more I read the thermometer may have been the single most important change. Practice and confidence also help I am sure. I no longer panic if I have issues. I also have modified a spreadsheet so my numbers are spot on for my system. That helps a lot with the issues that can cause panic.

Last thought, are you still using the bag you stove topped with?


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## ArcLight (12/10/12)

I use a voile bag. On the stove top I used a cotton laundry bag.

>>Also why the comment on low mash temp? You need to mash at the correct temp. Will not or should not be much difference between brew styles for mashing. Not enough to make any difference in conversion.

When I say "low temperature" what I mean is 65, which is lower than some use (68 for example).
Beta Amylase denatures much faster as the temperature rises, and in a thin mash its not as well protected as in a thicker mash. If the correct temperature is 68, I suspect a very thin mash will result in faster denaturing of teh Beta Amylase and teh final gravity will be higher than desired. Or maybe one wants that FG.

I do have a good thermometer, and do measure the temperature.
For now I wont worry much about the mash thickness, i will make sure I sparge. And also mashout.


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## katzke (12/10/12)

ArcLight said:


> Beta Amylase denatures much faster as the temperature rises, and in a thin mash its not as well protected as in a thicker mash. If the correct temperature is 68, I suspect a very thin mash will result in faster denaturing of teh Beta Amylase and teh final gravity will be higher than desired. Or maybe one wants that FG.
> 
> I do have a good thermometer, and do measure the temperature.
> For now I wont worry much about the mash thickness, i will make sure I sparge. And also mashout.



I BIAB because it is easy. I think you are getting too nerdy. If you want to sparge go 3 vessel and get it over with. If you want to BIAB then just follow the advice of old and add your grain bill to enough water at the correct temp, hold that temp for 60 to 90 minutes, raise the temp for a mash out, drain bag while bring to a boil, boil with your timed hop additions, chill or cube. Take the rest of the day off while others are cleaning up their 3 vessel systems.

Have you checked that thermometer? I do ice bath, boiling, and against a known good thermometer at mash temp. If it is a glass thermometer it will be good. If it is a dial thermometer who knows? If it is a digital, depends on the day and if you got the probe wet when you cleaned it last time.


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