spiny_norman
Well-Known Member
I’m having a fermentation issue that I just can’t figure out. I’m doing a Pliny clone published in Zymurgy. I used a slightly thinner mash (1.5qt per lb), hit my numbers perfectly (152) and mashed for 75 minutes maintaining a temp of 149 to 152 (I have a HERMS set up) before raising the temp to 168 and mashed out.
After a 90 minute boil the OG was 1.070 (exactly as the recipe says in the Zymurgy recipe, although I did have to increase the grain bill to get that). 5.5 gallons into the fermenter and I aerated using O2 for 2 minutes and pitched a 1 liter starter (WLP001). The recipe says the final gravity should be 1.011 which seems impossible.
After 9 days in primary fermentation stopped at 1.022 (I set the temp at 65 which had the wort temp at 68 during the most vigorous phase). I took another reading yesterday and it was still at 1.022 so I raised the temperature to 75 and roused the yeast by shaking the fermenter (being careful not to splash) and fermentation started again within a couple of hours and was going fairly strong when I left for work this morning. I guessing that if I’m lucky I might get it down another 4 points to about 1.018. Still too high for a DIPA.
So how the heck do they get it to 1.011? Even with an optimistic attenuation of 80%, using Noonan’s formula it won’t go lower than 1.014 (((1-0.8)*(1.070-1)+1) = 1.014.
Any advice? I’m out of ideas. I’m guessing at the brewery they do a regular C02 burst to rouse the yeast to prevent it from flocculating too early, but 1.011 still seems impossible with an OG of 1.070 unless I'm missing something obvious.
After a 90 minute boil the OG was 1.070 (exactly as the recipe says in the Zymurgy recipe, although I did have to increase the grain bill to get that). 5.5 gallons into the fermenter and I aerated using O2 for 2 minutes and pitched a 1 liter starter (WLP001). The recipe says the final gravity should be 1.011 which seems impossible.
After 9 days in primary fermentation stopped at 1.022 (I set the temp at 65 which had the wort temp at 68 during the most vigorous phase). I took another reading yesterday and it was still at 1.022 so I raised the temperature to 75 and roused the yeast by shaking the fermenter (being careful not to splash) and fermentation started again within a couple of hours and was going fairly strong when I left for work this morning. I guessing that if I’m lucky I might get it down another 4 points to about 1.018. Still too high for a DIPA.
So how the heck do they get it to 1.011? Even with an optimistic attenuation of 80%, using Noonan’s formula it won’t go lower than 1.014 (((1-0.8)*(1.070-1)+1) = 1.014.
Any advice? I’m out of ideas. I’m guessing at the brewery they do a regular C02 burst to rouse the yeast to prevent it from flocculating too early, but 1.011 still seems impossible with an OG of 1.070 unless I'm missing something obvious.