Underpitching?

[Evil Jalapeno]

I started a batch of Imperial Stout last night and ended up with an OG of 1.095. I only had on packet of Windsor dry yeast. So, three questions:

1. Is that enough yeast for a 23L batch?
2. Primary fermentation has started already. Can I still open the fermenter and pitch another packet of dry yeast in there, or is that an absolute no-no?
3. Can different strains of yeast be mixed in one batch (Windsor and Nottingham, for example)? What would be the result of mixing different yeasts?

Cheers!

[Al-Loves-Wine]

I would think that the attenuation would be different on two different types, so i would let one finish out, and if it wasn't dry enough you could always add another one. Others more experienced I'm sure will chime in.

I'm guessing that you will have some residual sweetness with one pack. What is the target FG supposed to be for your recipe?

[Chris Craig]

1. That was definitely an under pitch.  You'll likely end up with a higher final gravity than you expected to have. 
2. You can pitch more yeast.  Nothing bad will happen.
3. You can mix strains of yeast.  You'd get a mix of the profiles that each yeast provide if they're pitched close together.  You should be fine.

I suggest that as the fermentation activity starts to subside, you increase the temperature slowly.  The yeast will produce most of the flavour compounds in the first 4-6 days.  After that, the added heat won't affect the flavour of your beer much (if at all), but it will help with the attenuation.

[Evil Jalapeno]

Awesome. I'm gonna pitch another packet today and bring the heat up by a few degrees in a week or so. Thanks again for the great tips!

[Chris Craig]

You should raise the temperature gradually over a couple of days. Yeast don't like big changes in environment.

[Evil Jalapeno]

Well it's been 8 days now since I pitched the 2nd packet, and gravity has been stuck at .030 for days (was aiming for at least .020). I gently shook the primary 2-3 times to bring the yeast back in suspension, but nothing's happening anymore. I thought "screw it" and racked to secondary tonight, hoping that it may come down a little more during conditioning. Rookie mistake? Can I still bottle at .030 with less priming sugar than usual if the gravity doesn't come down in the next few weeks?

[Chris Craig]

There wasn't much more you could do there.  The stout will definitely be a bit sweeter than you wanted, but who knows, it could be the best thing you've ever tasted.

In the future, especially with big beers like this, pitch the proper amount (likely 3 packets in this), rehydrate the yeast in 30ºC water 30 minutes before pitching, and aerate the wort with bottled O2.  This will be your best chance of getting the proper attenuation.

[Evil Jalapeno]

Thanks again!