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Weisenbock stalled using WLP300

When I make big beers, I usually go with extracts. I just haven’t had much luck with my AG system going above 1.075. So, I brewed a weisenbock mostly according to Jamil’s book’s recipe:

6# wheat LME
1# amber DME
steeped small amounts of crystal,chocolate for color and flavor
Sterling for bittering only
3 gallon batch
WLP 300 Hefeweiss slurry (at least 300ml yeast)

My OG was 1.099 and fermenting at 64-66F (basement temp). I oxygenate with pure O2. Kraeusen formed and fermentation went well for about 3 days then slowed.
After two weeks I checked the gravity and tasted. Way sweet and gravity was 1.086. So I opened the airlock and shook the heck out of it. After another week, still sweet and I now have 1.080. So I hit it with oxygen again and brought the carboy upstairs where it is warmer. There’s a good inch of yeast on the bottom of the 3-gallon carboy so I know they multiplied. What do I need to do get this weisenbock to finish?

How are you measuring gravity? You’re gravities seem really ut of whack, I’ve seen 60% attenuation but not 20%. That measurement seems fishy. It could taste sweet at 1.035 which is where I think you’ll finish using DME/LME only and no sugar.

I recently brewed a weizenbock, OG 1.111 FG 1.024 with WLP300 (and later US05). I used some sugar and syrup to help the wort be more fermentable though. I also pitched a starter of US05 abtou five days in just because I was worried about the alcohol tolerance of the WLP300.

Check out Fred Bonjour’s big beer page, lots of good tips.

I’m measuring gravity by refractometer (% Brix). Here are my numbers with corrections for alcohol:
OG 23.3% = 1.099
After 2 weeks: 20.8% = 1.078
After one more week: 19.4% = 1.068 for an attenuation of 31%

After oxygenating and bringing up the temp to 68F, I now have some consistent activity in the airlock. I’ll see where this goes. I would think I should be able to get more than 10% attenuation/week out of this yeast. Maybe 64F was just too cool for the amount of sugar the yeast had to consume?

I fermented mine at about 65F, I don’t think that is why things are going slowly. Sounds like you did everything right, I’d wamr it up and keep rousing the yeast and let it go. You might add some active US05 to help clean things up, you should have good weizen character by now.

I tried my first weizenbock yesterday, not carbed enough but the flavors are excellent with some banana aroma.

Another week gone by and I’m only at 1.061 for 38% attenuation!

What do you think about adding a slurry of WLP 830 German Lager? I could put it in the garage at 50F and see what happens.

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