Okay, so I recently got back into brewing after a long time off. So far I've done 8 batches and all have had a problem with high final gravities. I think I've addressed all the obvious things - I double checked the hydrometer and thermometer, started mashing lower (around 148-150), pitch larger volumes of yeast, aerate more thoroughly, leave the beers longer in the primary, etc.
For example, my latest batch is a bitter (5 gal) with an OG of 1.040 from a base Marris Otter with .5# 50L crystal and that's it. I aerated with a pump and airstone for 30 min, pitched the yeast (Wyeast 1450) from a 2L starter at 65F. Fermentation took of right away - ambient temp in the basement is 60F (air temp) so I'm guessing the ferment temp was mid 60s. After 4 days a sample was at 1.030, so I roused the yeast and moved upstairs (ambients temp 70F). It's been there for a week, and samples the last three days have been steady at 1.024. That's less than 50% attenuation.
The other batched have been similar, but some have used a pack or two of dry yeast (some Notty, mostly S-05) and others have been directly on the yeast cake of an earlier batch. The resulting beers have, surprisingly to me, been drinkable - nothing all that sweet, no off flavors, etc.
Any ideas what might be going on here? I know my fermentation temps have been on the low side, but they seem to get going fine and I generally bring them upstairs where it's warmer once it slows down. The only other consistent thing is the aeration system, but shouldn't even terrible aeration should do better that 1.040->1.024 (with a big starter)? And pitching a lot of dry yeast did similarly, and as I understand it they're less sensitive to aeration.
Maybe I'm really messing up the mash - if I'm producing a ton of unfermentables then the yeast are doing the best they can and no amount of pick volume, aeration, etc will fix it. That would also explain why the don't taste sweet. But I don't understand what I could be doing wrong - I've been paying close attention to the mash temp the last few batches, and to be safe I've been letting them go 90+ minutes. I'll do a conversion test next time, but I have a hard time believing that's the problem - how could that happen so consistently across several batches if the thermometer is fine? My water is Great Lakes water from the Chicago municipal system, treated with campden, and the last few batches have used 5.2 ph stabilizer in the mash just in case. Some of the mashes have had some gypsum as well, but certainly not all.
Any other ideas?
For example, my latest batch is a bitter (5 gal) with an OG of 1.040 from a base Marris Otter with .5# 50L crystal and that's it. I aerated with a pump and airstone for 30 min, pitched the yeast (Wyeast 1450) from a 2L starter at 65F. Fermentation took of right away - ambient temp in the basement is 60F (air temp) so I'm guessing the ferment temp was mid 60s. After 4 days a sample was at 1.030, so I roused the yeast and moved upstairs (ambients temp 70F). It's been there for a week, and samples the last three days have been steady at 1.024. That's less than 50% attenuation.
The other batched have been similar, but some have used a pack or two of dry yeast (some Notty, mostly S-05) and others have been directly on the yeast cake of an earlier batch. The resulting beers have, surprisingly to me, been drinkable - nothing all that sweet, no off flavors, etc.
Any ideas what might be going on here? I know my fermentation temps have been on the low side, but they seem to get going fine and I generally bring them upstairs where it's warmer once it slows down. The only other consistent thing is the aeration system, but shouldn't even terrible aeration should do better that 1.040->1.024 (with a big starter)? And pitching a lot of dry yeast did similarly, and as I understand it they're less sensitive to aeration.
Maybe I'm really messing up the mash - if I'm producing a ton of unfermentables then the yeast are doing the best they can and no amount of pick volume, aeration, etc will fix it. That would also explain why the don't taste sweet. But I don't understand what I could be doing wrong - I've been paying close attention to the mash temp the last few batches, and to be safe I've been letting them go 90+ minutes. I'll do a conversion test next time, but I have a hard time believing that's the problem - how could that happen so consistently across several batches if the thermometer is fine? My water is Great Lakes water from the Chicago municipal system, treated with campden, and the last few batches have used 5.2 ph stabilizer in the mash just in case. Some of the mashes have had some gypsum as well, but certainly not all.
Any other ideas?