Imperial Stout OG too low

Hi folks. I brewed the N.B. Imperial Stout extract kit, followed directions to a T except for going to 4 1/2 gal hoping to boost the O.G. just a bit. But instead of 1.086 it came to 1.062. It’s bubbling nicely so I’ll probably end up with a decent stout, but not an imperial. Any guesses on why the O.G. came out so low, and is it feasible to boost it by adding fermentables at this point? I’m about 2 days into primary fermentation.

Let me guess… You brewed a partial boil (2.5gals) and used water to top up to 4 1/2 gals?

If you did it’s called wort stratification. Not all the wort was mixed with the water. The sample you got was watered down wort. It’s relatively difficult to get the 2 to mix. No worries, all that churning from fermentation will ensure it mixed.

With extract batches you’ll get the desired (or within a point or 2) if you use all the extract and hit the desired volume. If you only topped off to 4 1/2 gal you actually have a much higher OG, actually closer to 1.100. Expect that beer to have a higher FG unless you pitched a healthy amount of yeast and aerated well.

Loopie is right.
Next time stir your beer up hard before adding the yeast then get OG read.

I’m sure you guys are right, thanks for the responses. It just surprised me because that didn’t happen on previous batches. I pitched two very fat smack packs and swished it around pretty well so I’m hoping to end up in the 10% - 11% range.

Which makes me think of another question. Say I’m two or three months into the secondary and the FG is still a little too high. Is it feasible at that point to pitch some extra yeast and aerate a bit, or will the aeration at that point have some bad effect on the beer?

Your wort was harder to mix because of the VERY high OG. With a partial boil your initial OG before your top up water was closer to 1.175-1.180! that’s going to be hard to mix thoroughly.

DO NOT ADD O2 NOW!!! That will oxidate the beer. Big beers like this need time, so that’s first. When it hits FG you can try to add a yeast with a higher tolerance to ABV and with a higher level of attenuation. However, a beer like this should have a bigger body. Attenuating it too much will result in thinning it out.