My stouts always get stuck during fermenting.

[matt76]

No matter what I brew kits or all grain my stouts and porters seem to stop at about 1.020.

Only have a issue with stouts.

I seem to get this too, not every time but often with dark beers.

I also have similar problems, not just with stouts but - to some extent - all dark beers.

What yeast(s) are you happy with that'll ferment out dark beers?

I have encountered a similar problem but I think only with imp stouts. Not sure I have ever hit the target gravity and quite a few have appeared stuck.

Let me ask all of you, what FG are you expecting from a Stout or other dark beer, and why?

@foxy is absolutely correct that things like recipe, mash temp etc etc etc can all have an impact.

BUT - let me tell you my working theory:

Brewer's Friend for sure (and maybe other calculators, don't know, haven't tried) seems to massively over estimates the fermentability of your dark grains, and hence predicts a lower FG than you'll actually get.

Note I've sussed this out it is repeatable and predictable for all my dark beers such as Porter and Stout.

(I mash all my beers at 67degC yet I only see this behaviour in dark beers - so it's clearly not driven by mash temperature)

The effect will be all the worse and more noticeable if you're making lower strength beers as I do, because the proportion of highly fermentable pale malts (base malt, and stuff like Vienna and Munich) will be lower.

If you want to know how to work around this behaviour in your brewing software, and get a better idea of what FG to expect in reality, I posted something here just the other day.

 

[The Baron]

I think Matt is probably right. The more malts like Munich Vienna and crystals etc it seem to affect the FG.
I do not generally have a problem as I do not do many Stouts, Porters and very rarely have a problem with my beers as they are light or mid range. I do notice a difference when using Munich and Vienna which I do in my pseudo English/Marzen ales and they finish slightly higher than expected infact I have done a darker brew for Crimbo and used a Trappist yeast and it has finished at 1018 which I never see but I am ok with that.
Ps I use Brewers Friend

 

[matt76]

I think Matt is probably right. The more malts like Munich Vienna and crystals etc it seem to affect the FG.
I do not generally have a problem as I do not do many Stouts, Porters and very rarely have a problem with my beers as they are light or mid range. I do notice a difference when using Munich and Vienna which I do in my pseudo English/Marzen ales and they finish slightly higher than expected infact I have done a darker brew for Crimbo and used a Trappist yeast and it has finished at 1018 which I never see but I am ok with that.
Ps I use Brewers Friend

I don't see any major issue with Vienna or Munich, unless possibly if it's the darker types of Munich - but even then I doubt it as I don't see much issue with Amber Malt (25-30L) in my own brewing.

The problem is those dark/roasted malts, e.g. chocolate malt, roasted barley, Carafa 1/2/3, brown malt... etc.

I'm not totally certain about crystal malts - there are some credible suggestions that lighter crystal malts (maybe even up to as high as 100L) will add fermentables, but I have my doubts about much darker crystals such as Simpsons Extra Dark, Special B and Briess Extra Special.

Even though they don't add fermentables (or so I argue), of course all these dark malts do add to the OG, they add body and flavour.

Bottom line is, don't get too hung up on numbers like FG or even ABV - if the beer is good, drink it

 

[MartinF]

Let me ask all of you, what FG are you expecting from a Stout or other dark beer, and why?

@foxy is absolutely correct that things like recipe, mash temp etc etc etc can all have an impact.

BUT - let me tell you my working theory:

Brewer's Friend for sure (and maybe other calculators, don't know, haven't tried) seems to massively over estimates the fermentability of your dark grains, and hence predicts a lower FG than you'll actually get.

Note I've sussed this out it is repeatable and predictable for all my dark beers such as Porter and Stout.

(I mash all my beers at 67degC yet I only see this behaviour in dark beers - so it's clearly not driven by mash temperature)

The effect will be all the worse and more noticeable if you're making lower strength beers as I do, because the proportion of highly fermentable pale malts (base malt, and stuff like Vienna and Munich) will be lower.

If you want to know how to work around this behaviour in your brewing software, and get a better idea of what FG to expect in reality, I posted something here just the other day.

I think there's a lot of truth in what you say. In my most recent brew - a forecast 3.7% dark mild formulated by David Heath (see ), the predicted FG in Brewfather is 1010 for 3.7% ABV. As I mentioned in an earlier post, mine finished at 1016, resulting in an unacceptable (to me) 2.9%. As you say, the impact of high FG on low strength beers is profound. (After 2 weeks in the FV I added 300g sugar to 24L batch, plus a pkt of S-04 to give me another 5 fermentable degrees of gravity and 3.7%, but the FG was pretty much the same at 1015)

Yet neither David Heath, nor my equipment profile in Brewfather suggested an FG other than 1010 for this brew. (Ok, I had to make a few substitutions... Lallemand London instead of S-04, which was unavailable at the retailer at the time plus a couple of the malts), but it does seem like dark malts are producing less fermentable sugars than most(?) brewing s/w is taking account of.

Edit... After my substitutions, my predicted ABV was slightly higher than the DH recipe.

 

[MartinF]

The bottom line is, don't get too hung up on numbers like FG or even ABV - if the beer is good, drink it

... as long as the abv is in the ball park you're expecting!

 

[Chico1980]

Thanks for all the info.
Lots of things to think on. Glad it’s not just me who has this issue and it’s started some chat about why.
First step for me is to test out some yeast nutrient, and stick to just one yeast strain.
Current oatmeal stout has been slowly raised up to 22oc and is dropping gravity very slowly. Very slow fermentation, nothing like what happens with my lighter brews. Let’s see if I can fix this next time out.

 

[foxy]

From what I have read Wilko yeast is S04, 2 packets is more than enough, throwing yeast nutrient at it isn't the answer if you haven't got the sugars in the wort to convert to alcohol. The failure to reach FG required will be in the process or ingredients.

 

[moto748]

US-05 is my default yeast for stouts too. I've used MJ M42 too.

 

[moto748]

From what I have read Wilko yeast is S04,

It doesn't seem so to me, I have to say.

 

[Nicks90]

Darker malts tend have less fermentables, and I don't know but sure someone cleverererer than me can advise - but does things like choc malt and carafa3 affect the pH of the wart and consequently affect the yeasts ability to ferment?
If it bothers you that much, use a saison yeast. I accidentally pitched that in my experimental mushroom stout and it brewed out to 1.005

 

[MartinF]

Darker malts tend have less fermentables, and I don't know but sure someone cleverererer than me can advise - but does things like choc malt and carafa3 affect the pH of the wart and consequently affect the yeasts ability to ferment?
If it bothers you that much, use a saison yeast. I accidentally pitched that in my experimental mushroom stout and it brewed out to 1.005

Certainly, roasted malts are more acidic in the mash than pale malts. But brewing s/w should take account of that in calculating the mash pH.

 

[foxy]

Darker malts tend have less fermentables, and I don't know but sure someone cleverererer than me can advise - but does things like choc malt and carafa3 affect the pH of the wart and consequently affect the yeasts ability to ferment?
If it bothers you that much, use a saison yeast. I accidentally pitched that in my experimental mushroom stout and it brewed out to 1.005

Darker malts have the starches burned out of them at kilning, from dark crystal to light crystal the fermentable sugars are negligible, more in lighter than the darker crystals. Your right about the saison yeast it takes no prisoners.
The darker malts do affect the pH of the mash, only if they are put in at mash temperature. The darker malts are only there for colouring and flavour so don't have to be mashed, unless the brewer wants some astringency in a dry stout.
Steep, or adding the non fermentables at mash out leaves the pH in the same range as brewing a pale beer.
To get the best saccharification from the malt then a 1 hour mash at the lower end followed by a raise in mash temperature to the higher end for 1/2 hour to get the alpha and beta amylase enzyme to do their work.
Adding to much of the flaked oats would also cut down on the fermentable sugars in an oatmeal stout as the base malt has to convert not only its own starch but that of the flaked oats as well.

Not being cleverer than you, just read a lot about brewing stouts, next to English bitter stout is one of my favourites.

It doesn't seem so to me, I have to say.

Sorry Danstar Nottingham is what I read not 04

 

[moto748]

This thread got me wondering what is 'normal' for dark malt percentage. My stock stout recipe came out to 9% of the total. But that's including flaked barley in the total. And the dark malts too.

 

[foxy]

I keep my flaked oats around 17% of total grain bill, I 'No Sparge' so don't have to worry about stuck sparge. My roasted barley comes in around 8%.

 

[matt76]

Just for comparison, the Stout I currently have cold crashing is 30% dark & crystal malts whereas the Porter I have in the keg is 35%.

I use different yeasts in each but both typically start around 1.048 and end up around 1.018, so in that 3.5-4.0% ABV range. I've made them a number of times and the results are consistent.

 

[Cheshire Cat]

Just to add I made a West Indian Porter with this grain bill
10 litres
2200g Maris otter
180g flaked barley
180g roasted barley
80g crystal 140L
Plus 75g golden syrup and 75g Molasses
OG 1052
FG 1008
Attenuation 84%
Used a full pack of CML Five

 

[MartinF]

Just to add I made a West Indian Porter with this grain bill
10 litres
2200g Maris otter
180g flaked barley
180g roasted barley
80g crystal 140L
Plus 75g golden syrup and 75g Molasses
OG 1052
FG 1008
Attenuation 84%
Used a full pack of CML Five

That is a lot of roast barley for 10 litres (IMO)!
I'm assuming the OG & FG are your actual figures?

Purely for interest; banging that into brewfather, it comes out with...
OG 1062
FG 1014 (assuming a mash temp of 65C) => ABV 6.3%
Attenuation 75% (for some reason, brewfather has used this figure despite me entering the attenuation range as 76-84%, as per crossmyloof's description. Not sure why it would do that. If I set it to 84% attenuation, it predicts an FG of 1008 and ABV 7.1%)

 

[Cheshire Cat]

That is a lot of roast barley for 10 litres (IMO)!
I'm assuming the OG & FG are your actual figures?

Purely for interest; banging that into brewfather, it comes out with...
OG 1062
FG 1014 (assuming a mash temp of 65C) => ABV 6.3%
Attenuation 75% (for some reason, brewfather has used this figure despite me entering the attenuation range as 76-84%, as per crossmyloof's description. Not sure why it would do that. If I set it to 84% attenuation, it predicts an FG of 1008 and ABV 7.1%)

Real figures the issue is fermentation with dark malts mine came out fine. Ignore brew father as it assumes a BHE. My BHE was 60% due to full a volume mash. So the brew was OG 1052 FG 1008 ABV 5.8% which is fine.

 

[matt76]

Real figures the issue is fermentation with dark malts mine came out fine. Ignore brew father as it assumes a BHE. My BHE was 60% due to full a volume mash. So the brew was OG 1052 FG 1008 ABV 5.8% which is fine.

To be honest your result doesn't surprise me. You've got a mere 7% rosted barley and 3% crystal 140L. This is further skewed by your use of golden syrup (which I'm certain will ferment fine) and molasses (I'd assume will also ferment fine). These are effectively adding additional fermentable sugars which is similar to if you increased your base malt.

The supposed problem with poor attenuation in dark beers comes in my experience when the proportion of your dark (=> unfermentable) malts is much higher, e.g. the stout I have in the FV at the moment is about 5.5% each of roasted barley, chocolate malt, chocolate rye malt, caramunich and crystal 160L.