Brewing an Imperial Porter - Need Suggestions for Second Running Beer

I will be brewing an imperial porter with a gravity of about 1.086 to 1.088 this weekend and looking for suggestions for a second running's batch.

I haven't done it before and could use some help, including, wort collection and storage if necessary. With one burner and kettle, it will have to wait until the next day if the brew day runs late.

What can I make from the second running's, what kind of gravity can I expect, how much wort should I collect the second time around, and what amendments should I ad?

In the freezer I have plenty of DME and about a pound of Perle. I have some WLP530 stored from a Westy 12 clone too. Not sure how any of this would work but maybe a weird Belgiany porter with a pound of caramelized raisins, brown or Mexican sugar, or ...?

What is your initial grain bill? That will determine a lot fo the choices if you want to stay to style. I think just running a lower abv porter and making adjustments in the boil or fermentor would be the easiest thing to do. Different hops, more hops, winter warmer type with spices, etc.

The grist bill is ...

Amt Name %
9 lbs 8.0 oz Pale Malt, Maris Otter (3.0 SRM) 51.0 %
2 lbs 4.0 oz Barley, Flaked (1.7 SRM) 12.1 %
2 lbs 4.0 oz Mild Malt (4.0 SRM) 12.1 %
1 lbs Caramel Malt - 120L (Briess) (120.0 SRM) 5.4 %
1 lbs Chocolate Malt (450.0 SRM) 5.4 %
12.0 oz Oats, Flaked (1.0 SRM) 4.0 %
12.0 oz Wheat, Flaked (1.6 SRM) 4.0 %
6.1 oz Caramel/Crystal Malt - 80L (80.0 SRM) 2.0 %
5.0 oz Caramel/Crystal Malt - 30L (30.0 SRM) 1.7 %
5.0 oz Kiln Coffee Malt (165.0 SRM) 1.7 %
2.1 oz Black (Patent) Malt (500.0 SRM) 0.7

http://beersmith.com/blog/2011/10/07/parti-gyle-brewing-two-beers-from-one-mash/
http://morebeer.com/brewingtechniques/library/backissues/issue2.2/mosher.html

So your grain bill for a 10 gal batch gives us around OG 1.045 and SRM around 30. I quickly did these so don't quote me on them.
If you just split your batch in to 50/50 of the runnings you would end up with first 5 gal OG 1.07 SRM 40 and second 5 gal OG 1.035 SRM 20. Again guick guesses. You may need to add alittle DME to the imperial porter. This is how I have done it, just sparge with half the volume for the first running, then other half for second.

As far as waiting the next day, it shouldnt be a problem as long as nothing totally awful gets in there. You will be boiling it for 60 minutes, that should kill anything. I would just make sure it stays covered.
And as far as styles, I think that second runnings could be a mild or brown, if you dont really care about styles, just try something.

I have only done this twice, and only once by myself, and its been awhile, so any other input?

For the second beer, I downsized the original recipe to 2 gallons in Beersmith (sans hops and yeast), added the grains, about 4.5 pounds to the second mash, and collected about 4.5 gallons.

I added 1.5 oz. of fuggles at 60 minutes, 1 pound of grated piloncillo, 1 pound of caramelized raisins, and .5 oz. of fuggles at 15 minutes.

The raisins were hit with a propane torch to until the skin blistered and bubbled. I drew wort off the kettle, pureed the raisins, and dumped the slurry into the hop bag to keep the wort clean.

With a lid on the keggle, I boiled the first addition of hops and raisins for 30 minutes.

Post boil, the gravity at 3.75 gallons was about 1.068-1.070. I pitched an active slurry of WLP530 and let it go.

I decided not to add O2 for this batch, just to see how it goes. The fermentation chamber is occupied with the first batch so this one is sitting in the garage at an ambient temp of 64F. Measuring the beer internally, it is 70F.

Hope it tastes good.

That's a ton of flaked barley, plus a ton of flaked oats and wheat, nearly 4lbs. Why are you using that much? Also, nearly 2 lbs of crystal malt, and 1.5lbs of chocolate/black/coffee malt. Tons and tons of unfermentables. I'd expect a very high final gravity. Hope it turns out.

The recipe was formulated by Jeff Bagby; the target gravity is 1.018.

Well, about 37% of your grain is pretty much unfermentable. Getting about 80% attenuation will be tough. Getting 1.018 out of 1.088 is tough even under the best of circumstances.