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I have a beer which may or may have finished fermentation. I read about "stuck fermentation" and am wondering if I ended up with not enough fermentable sugars.

According to the calculator if i bottle it now it'll still be 3.5%, so very weak, but potentially still recovering a beer out of it. Or is this one for the drain?

The recipe was a dunkelweizen all grain jobby. It's been in the fermenter nearly 6 weeks now. I did try pitching another yeast, but nothing really happened, a bit of gas was given off, but then it just stopped.

The OG was 1.056. How do I know if the mash conversion was complete? I hit the OG that the recipe recommended so I took that as a good sign...

The fermentation temperature was about 18 degrees.. but i've hooked up a brew belt to bring it up a bit just to see if there is any life left.

  • What is your OG and your estimated FG? – Atron Seige Oct 30 '15 at 8:59
  • The OG was 1.056 How do i know if the mash conversion was complete? I hit the OG that the recipe recommended so I took that as a good sign.. – Codek Oct 30 '15 at 12:20
  • The fermentation temperature was about 18 degrees.. but i've hooked up a brew belt to bring it up a bit just to see if there is any life left – Codek Oct 30 '15 at 12:26
  • 18C seems a bit cold, aim for 22C and see what happens. – Philippe Oct 30 '15 at 12:30
  • Which yeast are you using? I've done two hefeweizens with Wyeast 3068, at similar OGs and similar temperatures (less than 18C), and hit roughly 1.015. – Matthew Moisen Nov 1 '15 at 21:27
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1.028 is ok, but generally only if you started A LOT higher.

First; try moving the fermenter to a warmer area and give it a bit of a swirl/shake to rouse the yeast. See if that helps.

Second: make a new yeast starter and pitch that. leave it for a while and see if it solves your problem.

Three: Taste the beer. If it tastes good, bottle and enjoy, else, bin it!

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    Based on the style of beer, an OG 1.056 should come down to about 1.016. Since he already pitched yeast for a second time, I dont think pitching again will help, unless adding yeast nutrients or something else? – Philippe Oct 30 '15 at 12:30
  • You are right @Philippe, a bit of nutrient will be a good idea for a second pitch, especially if you are not sure why your yeast decided to stop working. – Atron Seige Nov 16 '15 at 9:15
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It's rather high for a Dunkelweizen. I'd try gently swirling the fermentation vessel to get the yeast off of the bottom. Maybe up the fermentation temp a few degrees too. Do that and try taking some SG readings a couple of weeks later and see if you have got things moving along again.

I'd worry that if fermentation is just stuck (and not finished) that you'd be making bottle bombs.

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If the beer tastes good, there is no reason to throw it out.

You may not have any fermentable sugars left, after 2-3 days of stable gravity it usually means the yeast is done, you may bottle as it is but only if you are convinced that the fermentation is done.

To make sure fermentation is over, you can adjust the temperature since 18C seems a bit cold. Stirring things up a bit can also help to get yeast in suspension since most of the yeast may have flocculated after 6 weeks (or pitch some new if you prefer).

But, if your fermentation is done and you are not in a hurry, you can always add more sugar to raise the alcohol content. One cup of sugar in a 5 gallons batch will raise your alcohol content of about 0.5%. If you bring it to 4.5%, it will be a decent dunkelweizen.

Edit:

Adding some sugar will do one important thing. It will confirm if the yeast is active or dormant. If the added sugar is fermented, your will know for sure that your yeast doesn't need warming or shaking. If the consequence is only adding 0.5% of alcohol, it is a test worth trying in my opinion.

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  • If you downvote, add a comment as to why you felt the comment was inappropriate! – Atron Seige Oct 30 '15 at 9:00
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    I was about to ask for the same, thanks Atron. – Philippe Oct 30 '15 at 12:01
  • I also don't understand why this was downvoted? – Codek Oct 30 '15 at 12:19
  • One reason - it advised, when I downvoted, to add sugar, and/or bottle. Now imagine stored bottles when it gets warmer and yeast wakes up... bad things would happen! Now, when it mentions temperature, I undownvoted. – Mołot Oct 31 '15 at 6:49
  • Indeed, I was not suggesting to add sugar and then bottle, perhaps I was not clear enough. I think the answer is worth editing to make it clearer. – Philippe Oct 31 '15 at 13:55
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Take gravity readings every day for three to 5 days. if it does not change, chances are it is done and ready for bottling.

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The three Dunkelweizens I've brewed all finished high, 1.018, 1.022 and 1.017, and the style calls for 1.010 to 1.014, but I find the inclusion of wheat and munich malt is less fermentable than the lighter malts. I've used 3068 twice and a dry yeast from Mangrove Jack's (M20, which I don't recommend). I've also used 3333 in several weizens but not a dunkelweizen. Having said that, 1.028 is pretty high.

If it's not finished, you are in bottle bomb danger, especially if you over prime. As long as you have a safe place to store them, bottle bombs aren't the worst thing in the world, but they can shoot glass...

Probably your safest bet is to take a gravity reading, wait 5 days and take another gravity reading. If it hasn't moved, it probably won't move any further. If you have temperature control, raise it.

If you do bottle at that gravity, I would recommend trying a bottle once every 5 days or so, and if it gets super carbonated, move the entire batch to a fridge if you can. That will also help the fermentation subside.

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