fermentation not quite finished?

[beerisyummy]

Hello Zymurgists.

I just did my first BIAB brew with a full boil. (Up to this point I've been a partial-boil extract dude.)

It was a California Common, 8 lbs. 2-row, 1.5 lb. Vienna and 1 lb. Crystal 75L, Northern Brewer hops, with a 2-liter starter of WL810 San Francisco Lager yeast. Nothing out of the ordinary...

Everything went smoothly but I wasn't able to cool all the way to pitching temperature.

So I aerated the wort with an air pump/aquarium stone and let cool overnight.

The next morning I pitched the yeast. The wort temp was still a smidge high, at about 72°. Gravity reading was 1.053.

The initial fermentation was strong and steady, but not explosive (no blow-off), and appeared to be mostly finished in 48-60 hours. During this time the temp. strip on the glass carboy showed a cooling off to 66-67°.

Today, the 6th day after pitching, I took a hydrometer reading, and it shows 1.018. If I did the math right, that will give about 4.6% ABV - pretty much on target for a C.C. - and indicates 66% apparent attenuation, which seems a smidge low. (The hydrometer sample tasted great )

So for all those who enjoy helping others with their worries (and thank you!) I have the following questions.

1. Is the attenuation low, or should I not worry?

2. If it is low, is it off enough that there is any concern about "bottle bombs?" I would say probably not, but what do you say?

3. If you were me would you take any corrective action, or just let the beer finish itself up and bottle?

4. Options for corrective action could include:
(a) pitching more yeast (I made a 3L starter and saved 1L back, thinking I'd use it to grow another starter for the next steam beer - but I could just warm it up & pitch it in);
(b) rousing the yeast and/or warming the fermentation area (walk-in closet) with a space heater (in the past this has not been very successful for me);
(c) putting some yeast nutrient in there (which one?);
(d) re-aerating the wort/beer;
(e) some combination of the above.
Keeping in mind, I am all about simplicity and not tryina win a medal with this brew.

5. In retrospect, was the temperature decline enough to stall the yeast before it finished up?

6. In retrospect, did I aerate too soon? Does oxygen leave the wort if you just leave it sit?

My TIA to the hive mind!

 

[day_trippr]

1 - you're inside the manufacturer's attenuation spec, so presuming there are any more points to shave is an unknown.
2 & 3 - I would advise ramping the temperature back to ~68°F for a couple of days to assure fermentation is actually complete and eliminate grenade concerns.
4 - do not under any circumstances introduce O2 at this point, you will murder that beer. I'd say the same wrt adding more yeast. If you want to give the fermentor a gentle swirl to re-suspend the yeast and let it sit for a couple/few days, that's relatively harmless, but again I'd get the temp back up as well.
5 - I would consider the negative ramp suspect for this yeast strain, and would be interested if warming it a bit might drop the FG at all.
6 - I want to assume you left the fermentor sealed up while you let it sit overnight, just for bug-ingress-protection, in which case whatever O2 you infused could not have escaped.
That said, in a perfect world you want to pitch first and aerate second, to minimize oxidative effects on the wort.
And you should always think long and hard about introducing any O2 post-fermentation - and then not do it

Cheers!

 

[beerisyummy]

1 - you're inside the manufacturer's attenuation spec, so presuming there are any more points to shave is an unknown. Good point (pun intended)
2 & 3 - I would advise ramping the temperature back to ~68°F for a couple of days to assure fermentation is actually complete and eliminate grenade concerns. Easy enuf.
4 - do not under any circumstances introduce O2 at this point, you will murder that beer. I'd say the same wrt adding more yeast. If you want to give the fermentor a gentle swirl to re-suspend the yeast and let it sit for a couple/few days, that's relatively harmless, but again I'd get the temp back up as well.
5 - I would consider the negative ramp suspect for this yeast strain, and would be interested if warming it a bit might drop the FG at all. I'll reply to this thread when I know.
6 - I want to assume you left the fermentor sealed up while you let it sit overnight, just for bug-ingress-protection, in which case whatever O2 you infused could not have escaped. Yes, yes I did seal it.
That said, in a perfect world you want to pitch first and aerate second, to minimize oxidative effects on the wort. Hmmm hadn't run across that little nugget of info.
And you should always think long and hard about introducing any O2 post-fermentation - and then not do it Yeah - I guess this is either post-fermentation or very nearly-post-fermentation. Again, good point.

Cheers!