Repitching after rousing

[dirtfish]

Friday will be day 7 of fermentation of our first brew. We had a new 12*P pitch of BSI-7 (similar to WLP007/Wyeast 1098). Grist is 90% pale, 6% crystal, 3% wheat and 1% black. Single infusion rest @ 152*F for 60 minutes. (Although, mash in was too hot and temps exceeded 160 for up to 10 minutes, but we got settled at 152 by 15 minutes). 90 minute boil, Oxygenated at 2 liters per minute for 35 minutes. OG=12.8*P. Pitch at 68*F. Fermented at 68*F for 48 hours. Let rise to 70 and held for 72 hours. Reached 4.2*P on day 4 and now at 4.0*P. I was hoping to get below 3*P. I tried rousing the yeast with CO2 through the dump valve once at the end of day 5 and twice on day 6. I got yeast back up in suspension, but not getting any better attenuation. I am pretty sure that either the early high mash temp or not enough oxygen is responsible for the low attenuation.

I need to collect yeast to brew on Saturday or Sunday. Fermenter is now at 70*F. Do I need to lower the temp before trying to collect yeast for the next brew? I was planning to count and (hopefully) collect enough for this next brew, let the first batch sit on the remaining yeast for a few more days and try for a little more attenuation.

[DageraadBen]

My guess is that fermentation is done. It's a flocculent yeast, so all the yeast you want to harvest is back down in the cone. Anything else that settles in the next few days isn't something you want to re-pitch anyway.

[JsTX]

Fermentation is most likely done. 68% apparent attenuation is a little low for that yeast but considering the high mash in temp its to be expected. There's not much coming back from a 160*F mash rest. Even if it came back down to 152*F. I'd be hopeful that only a portion of your mash was at 160*F. Mash temps will stratify in single infusion tuns.

I try to avoid rousing before harvest until I dump the first portion of the cone. The settled trub, more flocculent dead or dying yeast, and protein has no business being forced back into suspension and could be detrimental to the flavor of your beer. After that, harvest away!! Never hurts to leave a little yeast in the cone after harvesting to rouse back up during diacetyl rest. Also with more flocculent english yeast strains get that stuff out of there asap after fermentation hits terminal. It will start tanking in viability exponentially day to day. Especially at 70*F

[dirtfish]

Thanks for the replies-
Fermentation was indeed done. I think the initial high strike plus low O2 was the problem.
JsTX-I learned most of what you said firsthand when I collected the yeast that I already roused. I don't think I got too bad of a flavor impact on the batch we collected from, but that stuff was hard to count and full of non-yeast type stuff...
We did get a good enough collection to practically blow the fermenter up on the repitch though. I'm close to terminal on batch two and collecting tomorrow (day 3 of fermentation). Hoping for better results this time.

[JsTX]

Glad to know everything worked out! Hope you get several more generations off of it too. Happy brewing!