Issues with slow end of frementation with BIAB method

[Zteelblade]

Hello, I am a still beginner at home brewing with some 1 year and 30 patches experience.
I use a crude old BIAB method, and one issue has been bothering me for some time. It has actually gone worse since I got new bigger pot for brewing 20l-->40l
I have read a lot and tried to figure out why my fermentation times are way too long. Even with yeasts like Kveik, my fermentation times are way way too long. They actually start vigorously, but then they go to "slow" mode with some small activity on airlock for like 2-3 weeks. It is pretty much like 98% done in 2-5 days and then 2% during the next 2 weeks. No kind of noticeable off flavours was detected. Beer has been good nevertheless.


I am certain that it is not about pitch rate or temperature. It even happens if I overpitch. And I am 100% certain that temperatures are not the issue here.
I was thinking about some kind of bacteria / old yeast left in the fermentation bucket after wash, but I am very precise with star san.

Then yesterday I got an idea of what might be wrong. But I am not 100% sure, but here is my theory:
I have always lived in the understanding that in BIAB the grinding fineness of grains does not matter since no stuck issues in BIAB. But I have always ground my grain very fine ... into pretty much flour. I have always had a thick mixed layer of yeast, grain, and other stuff in the bottom of fermentation after fermenting is done. That layer is quite thick compared to beer, around 5l out of 26l (on previous 20l cattle it was maybe 2-3l for 16l).
Could it be that this layer blocks yeasts from getting the fermentation totally done? And sugars from this layer slowly migrate into the liquid causing a slow and long "end" fermentation time?

 

[bracconiere]

What kind of final gravities are we talking?

 

[Zteelblade]

There is also another issue I had... I think my beers have been slightly on the dry side for at least a couple of patches... like 30-40% drier than expected but that might be also an issue with my mash temperature control. Like when expecting 1.014fg I get 1.010 or 0.009 instead for exmaple.

But most of the beers I made lately are commonly around 1.050-55~ OGish and 1.010-1.015ish FG, ofc mine finishing somewhat drier.

 

[Golddiggie]

What kind of 'bag' are you using where you get that much matter in your fermenter? What's the gap of you barley mill/crusher? IME, you don't want flour so much as cracking the husk/hull to expose the endosperm.

What temperature are you mashing at (if you're going to list metric, also list standard, so if C also show F since some of us don't speak Metricese).

The majority of my beers finish active/hard fermentation after about 3-4 days from going live. I give them at least another week (typically 10-14 days total) before I start any other processes, like my yeast harvest. With my three vessel system I don't get any visible grain particles into fermenter (any probably get caught in the whirlpool along with the hop matter and are left in the BK).

If you're getting lower FG's than expected, check your thermometer. I'd wager it's not reading correct and you're mashing much lower than you think.

 

[Zteelblade]

What kind of 'bag' are you using where you get that much matter in your fermenter? What's the gap of you barley mill/crusher? IME, you don't want flour so much as cracking the husk/hull to expose the endosperm.

What temperature are you mashing at (if you're going to list metric, also list standard, so if C also show F since some of us don't speak Metricese).

The majority of my beers finish active/hard fermentation after about 3-4 days from going live. I give them at least another week (typically 10-14 days total) before I start any other processes, like my yeast harvest. With my three vessel system I don't get any visible grain particles into fermenter (any probably get caught in the whirlpool along with the hop matter and are left in the BK).

If you're getting lower FG's than expected, check your thermometer. I'd wager it's not reading correct and you're mashing much lower than you think.

What's the gap of you barley mill/crusher? IME> There isn't partially any cap tbh I put it as close as possible w/o getting friction from empty milling. I use corona style of mill.

I tested my temperatures with 3 thermometers (1 being integrated with kettle) and they give similar readings with maybe 1C(1.8F) difference. I hit pretty close to the intended FG's with that old smaller kettle with the same 2 thermometers. I usually mash around 66-68C (150F to 154.5F), depending on recipe. > Anyway I try next time to mash +1C / + 1.8F higher and see if I get closer FG results then.

 

[Zteelblade]

Oh and the bag I am using looks like this:
(at least it is intended for brewing and is sold in respected brew shop here)

 

[Golddiggie]

Your bag looks sketch dude. The one for the grain too.
No idea where you're located, since you didn't have anything showing (under your name).
I never went for the cheap 'corona' type mill. Used a 'barley crusher' first until it wasn't what I liked and upgraded to a Monster Mill (2 roller) back in 2011. Never looked elsewhere. Always get spot on crush, and I set the gap depending on what my gear was optimized for (changed for the Spike MT most recently).
If you're getting a lot of 'flour' then you need to adjust your crush. You're not making bread, you're making BEER.
I'd also get a finer mesh bag than what that thing looks like. Appears to have wide mesh on the bottom which will allow your flour through. Maybe with a better crush level it would work.
Also, 150 will be more light body (lower FG) where 154 is in the upper reached of medium body. How often are you checking the temperature? How long is your mash? Are you checking for conversion? A 2F variance is actually quite a lot for during a mash.
Are you thermometers analog or digital? Have you calibrated them to a known temperature item? Doesn't matter if they're within 2F of each other if they're all off on set temperature items.

 

[Sammy86]

But I have always ground my grain very fine ... into pretty much flour. I have always had a thick mixed layer of yeast, grain, and other stuff in the bottom of fermentation after fermenting is done.

Ease up on the crush...you don't want too much flour

Even with yeasts like Kveik, my fermentation times are way way too long.

You need to remember, yeast are a living organism. They are going to do what they want...no matter how much we groom and please them before pitching. Sometimes, they take longer. Standard is 10-14 days so you're not ridiculously long.

I was thinking about some kind of bacteria / old yeast left in the fermentation bucket after wash, but I am very precise with star san.

Starsan is not a cleaner. What are you using to clean the vessel you are using to mash and boil in?

 

[camonick]

They actually start vigorously, but then they go to "slow" mode with some small activity on airlock for like 2-3 weeks. It is pretty much like 98% done in 2-5 days and then 2% during the next 2 weeks.

Are you using airlock activity to determine the progression of fermentation or are you measuring the gravity after a couple weeks. If you’re just looking for bubbles in the airlock, the finished beer will off gas dissolved CO2 long after fermentation has reached final gravity.

 

[Stormcrow]

I was

Are you using airlock activity to determine the progression of fermentation or are you measuring the gravity after a couple weeks. If you’re just looking for bubbles in the airlock, the finished beer will off gas dissolved CO2 long after fermentation has reached final gravity.

Wondering about that myself. The airlock can bubble long after fermentation is done due to rising temperature, change in barometric pressure, disturbing the fermenter, etc. OP may have been actually been tracking gravity drop throughout the slow finish, but if not.....

 

[GrowleyMonster]

I also get a long tail-off of fermentation activity. For that last 2% or so, you might try going to keg at 5 or 6 days and compare that to going the full 3 weeks or whatever. You will probably find a slightly different flavor profile and maybe like the young beer well enough to just blow off that last couple weeks of very low activity.

Iike you, I wondered if all the fines might be interfering with the fermentation a bit, and so I have in the past (with the airlock still in place, of course) given the BMB a good swirl, enough to temporarily suspend the trub, a few days in. This usually results in a brief period of fairly high activity. I still haven't decided if that actually does me any good or not.

 

[Zteelblade]

Thank you all for replies:
Few responses:
1) I think mill and bag are ok, I have ground my grains fine on purpose since I lived in understanding it does not matter on BIAB. I can adjust my mill and make coarse. I think I will try it next time.
2) About Starsan > Sorry I used the wrong term, not a native English speaker here I use Starsan for sanitation and Chemipro oxi for cleaning.
3) I determine fermentation based on bubbling at the start but at the end, I just look top of the fermenter (plastic is transparent) and see if there are still some small patches of foam forming on the top. I can see small activity there all the time, also airlock releases a bubble once per hour or so. When that stops and the surface gets clear I consider it done.
There should not be major temperature changes, I use a temperature control bag, and ice bottles during active fermentation.

I just wonder why my properly pitched kveik yeasts take 2 weeks or more to ferment while brewers say it should be done in few days. I can understand that If I would be making lager or something like that.

 

[Miraculix]

Are you taking gravity samples are you just watching your airlock? If you are just looking for bubbles as an indicator of fermentation, forget about it. It will stay bubbly long after fermentation already finished and sometimes there are no bubbles although fermentation is still going.

 

[Zteelblade]

Are you taking gravity samples are you just watching your airlock? If you are just looking for bubbles as an indicator of fermentation, forget about it. It will stay bubbly long after celebration already finished and sometimes there are no bubbles although fermentation is still going.

I check also the surface of the fermenter (transparent) and see if there are still small foam patches forming. Once they disappear I consider it finished.

 

[Miraculix]

I check also the surface of the fermenter (transparent) and see if there are still small foam patches forming. Once they disappear I consider it finished.

That is also no sign of active fermentation. Air pressure changes due to weather conditions and temperature changes will also have the same effect. They release dissolved co2 which will form foam and generate bubbles.

 

[Zteelblade]

I guess I will get one of those wifi temperature/gravity measure units then. Had a plan to get one for some time. Then I can see the graphs.
I don't have a tap in my bucket and I don't want to let oxygen in by taking measurements.

 

[Sunfire96]

Gravity measurements are the best way to determine if fermentation is complete. I've had two brews with kveik be finished fermenting but still had a quarter inch of krausen on top in the fermenter

 

[Miraculix]

I guess I will get one of those wifi temperature/gravity measure units then. Had a plan to get one for some time. Then I can see the graphs.
I don't have a tap in my bucket and I don't want to let oxygen in by taking measurements.

These are also very unreliable. They are a fun thing to watch and give you an idea of the direction you are going, but don't reliably tell you what's going on in there in detail.

 

[RM-MN]

I was thinking about some kind of bacteria / old yeast left in the fermentation bucket after wash, but I am very precise with star san.

Hot water kills bacteria. With your clear fermenter you need to be careful with how hot the water is or it will distort the plastic. Water over 150F will pasteurize, hotter works faster.

What's the gap of you barley mill/crusher? IME> There isn't partially any cap tbh I put it as close as possible w/o getting friction from empty milling. I use corona style of mill.

The trub you see in the fermenter is a mix of grain particles, break material, and yeast. In actual measurement, I suspect your grain particles are only a very small part of that. If you aren't getting enough beer with that trub being left, add water and grain to the mash. My Corona mill rubs when empty.

1) I think mill and bag are ok, I have ground my grains fine on purpose since I lived in understanding it does not matter on BIAB. I can adjust my mill and make coarse. I think I will try it next time.

If you adjust the mill to get more coarse grain, expect your brewhouse efficiency to go down. Mine did.

3) I determine fermentation based on bubbling at the start but at the end, I just look top of the fermenter (plastic is transparent) and see if there are still some small patches of foam forming on the top. I can see small activity there all the time, also airlock releases a bubble once per hour or so. When that stops and the surface gets clear I consider it done.

Bubbles in the fermenter or in the airlock are there simply to entertain the brewer. Beer will outgas CO2 for a long time after fermentation is complete. While I often leave my beer for 3 weeks so more of the yeast and trub are settled out, I have bottled in a week with fermentation being complete. Use a hydrometer to tell if the fermentation is complete.

It is said that brewers make wort, yeast make beer and yeast don't always follow the rules. As a brewer you have some control over the final gravity by your choice of yeast. With your grain milled as fine as you have yours, control of the fermentability is lost because the conversion of starch to sugar happens before any denaturing of the beta amylase can occur. You might want to experiment with how long that takes by scoping out a little of the grain from the mash and putting a drop of iodine on it to see if it turns blue indicating starch left in it. Hint: It does not take an hour for BIAB to get full conversion. Regardless of your experimental results, do not stop the mash too soon or you get beer with no flavor. I recommend no less than 30 minutes.

 

[jtgoral]

In my case yeast does not know that I extracted sugars using BIAB. Does your yeast know?

 

[soccerdad]

I'm curious to know if you have ever made a saison using diastaticus yeast. Diastaticus can linger in a fermenter and it attempts (sometimes) to keep going well below 1010

 

[IslandLizard]

I think mill and bag are ok,

I don't think so.
The bottom mesh is very, very coarse/open. That causes a fair amount of your powder-fine grist to drop through. Specially when agitated.
The mesh in the top part of the bag looks more standard BIAB mesh from what I see, the whole bag should be more like that.

 

[beernutz]

These are also very unreliable. They are a fun thing to watch and give you an idea of the direction you are going, but don't reliably tell you what's going on in there in detail.

If you're referring to the Tilt I would disagree with the very unreliable description based on my 3 years of usage.

In about half my batches I'll do an OG hydrometer reading and I have yet to take one that's more than .002 different from the Tilt's OG reading.

The ending gravity readings aren't as precise, my theory is due to gunk collecting on the Tilt, but I get a good idea of a completed fermentation when I see they haven't changed at all for a day or so.

I'm only concerned with an accurate OG and seeing when a steady FG has occurred and not really so much the measurements in between. I'm going to leave the beer in the fermenter long after it appears to have reached FG anyway.

 

[IslandLizard]

No idea where you're located, since you didn't have anything showing (under your name).

@Zteelblade
It's helpful for others to see where you're located. You're not in the U.S. which is where most of our member base is.

Adding your location (it's in your user settings) takes much guesswork and such out of the advice equation.

 

[VikeMan]

Oh and the bag I am using looks like this:
(at least it is intended for brewing and is sold in respected brew shop here)
View attachment 740481

IMO, the bottom of that bag plus a fine grind can completely explain why you're getting malt particles in your fermenter. I can't say that I've ever seen a bag intended for brewing with a mesh that open.

 

[Miraculix]

IMO, the bottom of that bag plus a fine grind can completely explain why you're getting malt particles in your fermenter. I can't say that I've ever seen a bag intended for brewing with a mesh that open.

I think I had the same bag.... I bought a new one for the given reasons, after using it a few times. It is not a nice bag, no idea who designed that one. The sides of it are totally fine, but the bottom part... nope. I had a lot of malt particles in my beer. After swapping the bag, all good, even with a very fine crush.

 

[JJinMD]

Thank you all for replies:
Few responses:
1) I think mill and bag are ok, I have ground my grains fine on purpose since I lived in understanding it does not matter on BIAB. I can adjust my mill and make coarse. I think I will try it next time.
2) About Starsan > Sorry I used the wrong term, not a native English speaker here I use Starsan for sanitation and Chemipro oxi for cleaning.
3) I determine fermentation based on bubbling at the start but at the end, I just look top of the fermenter (plastic is transparent) and see if there are still some small patches of foam forming on the top. I can see small activity there all the time, also airlock releases a bubble once per hour or so. When that stops and the surface gets clear I consider it done.
There should not be major temperature changes, I use a temperature control bag, and ice bottles during active fermentation.

I just wonder why my properly pitched kveik yeasts take 2 weeks or more to ferment while brewers say it should be done in few days. I can understand that If I would be making lager or something like that.

If you are trying to chill the kveik to non-kveik (but more typical) fermentation temperatures, then that would be why it is taking so long. Kveik can be done in a few days, but you have to keep the temps much higher, like 90-95F in order to accomplish that. Also, people have reported that some of the kveiks need additional nutrients for fermentation. I can't give much feedback for that, because I typically just add some yeast nutrient to every batch I brew.

As stated earlier, your over-attenuation is probably related to your mash temp. You have to realize that as you increase the volume of your mash vessel, you increase the variation in temps throughout that vessel, there is going to be a temperature gradient from top to bottom. You can somewhat fix that with recirculation or stirring. For that you kind of have to play around with how much and when and experiment some to figure out how your equipment behaves so you can be more consistent from brew day to brew day.

 

[Sunfire96]

I had a bag like that but after a few brews I replaced it with a cheapo paint strainer bag from The Depot. I think the large bottom mesh is supposed to mimic a false bottom in a MLT that you draw wort through a ball valve to your kettle, which is not how BIAB usually works.

As far as attenuation, double check mash temperatures and thermometers, ensure good yeast health and fermentation temperatures, and maybe try siphoning to your fermenter to prevent less "stuff" from getting in?

Tilt hydrometers can be accurate, but not precise. There's a difference. The most reliable way to check fermentation is completed is steady readings 3 days apart using a hydrometer or refractometer

 

[Miraculix]

If you're referring to the Tilt I would disagree with the very unreliable description based on my 3 years of usage.

In about half my batches I'll do an OG hydrometer reading and I have yet to take one that's more than .002 different from the Tilt's OG reading.

The ending gravity readings aren't as precise, my theory is due to gunk collecting on the Tilt, but I get a good idea of a completed fermentation when I see they haven't changed at all for a day or so.

I'm only concerned with an accurate OG and seeing when a steady FG has occurred and not really so much the measurements in between. I'm going to leave the beer in the fermenter long after it appears to have reached FG anyway.

That's what I meant, og is fine but as soon as bubbles and yeast rafts etc. Come into play it's a bit of a gamble because stuff can stick to the tilt. That obviously falsifies the reading and the stuff obviously can get loose again, which again changes the reading....

I also don't take readings for oxygen reasons, I just stick to my rule of two weeks and it's done, unless I have s finicky or sta+ (saison) yeast. Then it's three weeks in the fermenter. There's a certain risk but that's ok for me. The worst I had was a bit of overcarbonation Once with lallemand verdant IPA after 9 days. So that one is now two to three weeks in the fermenter and all is good.

 

[z-bob]

If you have an extra $150 to throw at it, get a Tilt hydrometer and monitor your specific gravity and temperature in real time. You'll probably find that your beer is >90% done in two days, and totally finished a week after that.

 

[IslandLizard]

If you have an extra $150 to throw at it, get a Tilt hydrometer [...]

A different view:
Yeast does it own thing, it will finish where it does, not much you can change about it. The Tilt is not going to improve that or your beer, it's just a gadget. Instead, if you have that kind of money to spend, maybe put your $150 toward a better fermenter so you can keep oxygen out, and do closed transfers.

 

[Zteelblade]

Ok thank you all, I guess I'll get another type of bag then. Too bad I just ordered 2nd such bag, since my first one already has been used for like 30-40patches
And probably at some point will get Tilt measurement tool too. And I will reduce the fineness of milling. Ill try to use the bucket next time with a tap. Only issue is that the tap hole is often covered with the turb and grain :/ But maybe it will work with the coarser grind.

Any recommendations on which bags are good for BIAB?

 

[Miraculix]

Ok thank you all, I guess I'll get another type of bag then. Too bad I just ordered 2nd such bag, since my first one already has been used for like 30-40patches
And probably at some point will get Tilt measurement tool too. And I will reduce the fineness of milling. Ill try to use the bucket next time with a tap. Only issue is that the tap hole is often covered with the turb and grain :/ But maybe it will work with the coarser grind.

Any recommendations on which bags are good for BIAB?

Never owned one myself but heard nothing but good stuff about the bags that @wilserbrewer makes!

 

[IslandLizard]

Any recommendations on which bags are good for BIAB?

Never owned one myself but heard nothing but good stuff about the bags that @wilserbrewer makes!

Wilser BIAB Bags. They're made for your kettle.
https://biabbags.webs.com/
You can contact him here on HBT, privately, by starting a "conversation" with him.

 

[Sunfire96]

Ok thank you all, I guess I'll get another type of bag then. Too bad I just ordered 2nd such bag, since my first one already has been used for like 30-40patches
And probably at some point will get Tilt measurement tool too. And I will reduce the fineness of milling. Ill try to use the bucket next time with a tap. Only issue is that the tap hole is often covered with the turb and grain :/ But maybe it will work with the coarser grind.

Any recommendations on which bags are good for BIAB?

You're doing 20 L batches? Too big for a paint strainer. I had a BrewBag that I liked a lot, but have heard great things about Wilser Bags

 

[Bobby_M]

Don't be so sure about your fermentation temperatures not being a factor. I think that's what it is. Fermentation needs to be kept cooler at first but then it's just as important to be sure it doesn't start cooling off towards the end as it slows the yeast down quite a bit. For a typical ale, it should be kept at about 18c internally or 16c ambient. After fermentation peaks and begins to wane, you'll want to keep the temps steady with heat (or less cooling) or even raise the temp up to 21-22c for the rest of its time in fermentation.

Kviek is another animal altogether and should be held at 30-35c.

 

[Zteelblade]

You're doing 20 L batches? Too big for a paint strainer. I had a BrewBag that I liked a lot, but have heard great things about Wilser Bags

Im doing 26-27l mostly,my kettle is 40l but fermenter with foam can take no more than that, even less if doing abbey ales etc...

 

[Zteelblade]

Kviek is another animal altogether and should be held at 30-35c.

I know but i was doing pseudo lager with lutra and it is recommended to hold it around 20-22c at start

 

[JJinMD]

I know but i was doing pseudo lager with lutra and it is recommended to hold it around 20-22c at start

And that is why it was fermenting longer than you expected. Kviek only runs fast when at higher temperature. Your fermentation time is typical for kviek at the temperature you were at.

 

[Bobby_M]

I know but i was doing pseudo lager with lutra and it is recommended to hold it around 20-22c at start

Ok that's fair, but my statement about pushing the temps after peak fermentation still stand. Vigorous fermentation makes a lot of heat. When it slows, it cools and yeast slow and/or crash out too early.

I just kegged a Marzen fermented initially at 50F (10c) for 5 days, then a ramp up to 60F (15c) for 3 days and then 65F (18c) for the final 7 days. Fermentation was visibly done (and gravity verified at 10 days for a 6% ABV). No fermentation character or off flavors.