I just had an issue with an oatmeal stout. I'm just starting to brew beer at home (BIAB) and I think I made some mistakes.

I had my water at 80°C hoping for the decrease of temperature to 72°C when adding my grains. So I just kept at it not knowing this was a problem. So my OG was at 1.070, recipe indicated it should be at 1.068. Then I put the beer in the fermenter and after 7 days the gravity dropped to 1.031, after 6 more days gravity was still at 1.031. I added another pack of Yeast Safale S-04, swirled around hoping for yeast to activate. A week later, nothing. Gravity was still at 1.031. So I just bottled after adding some priming.

A week later, my beer is flat and has too much body. Carbonation seems to be not happening (or struggling) since the beer is too dense.

Another strange thing I experienced was my airlock sucking my sanitizer solution into the fermenter. I don't know if this may affect something in the fermentation.

I'd really appreciate some insights if you know what is happening here. Cheers!

  • The airlock solution is usually sucked in when the fermenter is hot. Let it cool a little more before adding the liquid in the airlock.
    – Philippe
    Commented Nov 13, 2019 at 17:25
  • 2
    As JesseB pointed out, your mash temperature was too high and you picked up too many unfermentable sugars. You probably want to read about alpha and beta amylase and how temperature of mash impacts fermentability of wort. There is plenty of material around on that topic. If this happens to you again in the future, don't bottle the beer. Brew another one (let's call it dry stout) and try to ferment it as dry as possible (low mash temperature and yeast that dries it out), mix two batches and then bottle. You can do it now as well and then mix before drinking. Cheers!
    – MaliMish
    Commented Nov 14, 2019 at 8:21
  • Hey, @MaliMish You're right about the temperature and the unfermentable sugars. I read about alpha and beta-amylase, thanks.
    – Gabriel
    Commented Nov 19, 2019 at 0:03

2 Answers 2


At what temperature did you eventually mashed? Not sure how it works out with BIAB, but adding grains to a regular mash (even less volume compared to BIAB), the temperature only drops a few °C's. My guess is that if you added the grains at 80°C, you mashed at around 76/77°C. This is way too high, but 72°C is also too high. Mash temps range from 62-70C°, above that results in too much unfermentable sugars and thus a high FG.

What kind of sanitizer solution got into the fermenter? Most of them do no harm to the yeast, at least not in small quantities. Give it some more time, it can take more than a week to properly carbonate.

  • Hey. You're right about the temperature and the unfermentable sugars. I used a peracetic acid solution in the airlock. I'm guessing this is ok. On the other hand about the carbonation, after two weeks it seems to be happening ok. Ther is some acceptable krauzen at the top when is just served, but after a few minutes, it just fades away completely. Also, carbonation doesn't feel in the mouth when I drink it. I hope my brewing abilities get better so the next batch is way better than this one.
    – Gabriel
    Commented Nov 19, 2019 at 0:19

If you achieved the target gravity, then the mash worked OK.

Due to the high temperature (producing unfermentable long-chain sugars) and the inclusion of the oatmeal - which contains a lot of unfermentable starches (and that's why we use it), you would be expecting a high final gravity. Granted ~1.030 is about 5-10 points higher than where I'd expected that to finish, but then again, I've never mashed at 80°C, and maybe you used a lot of oats.

It often takes more than a week for carbonation, especially in a higher-alcohol beer. Just wait a couple of weeks.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.