How can you lower a final graity after attenuation?

[brewinhard]

I agree with Bug. I would leave the beer on the primary yeast cake which is your best shot to further attenuate your final gravity you are at now. Let the beer warm up to room temps and give your fermenter a good swirl to resuspend the yeast to help get it going again. Let it go for another week or so, being sure to swirl every other day and then check the gravity. If it drops a few points then continue doing this until it stops.

If you don't see a change in the gravity at all after doing this, then you could try to make a small pint sized starter of a strong attenuating yeast (US-05, or champagne yeast) and pitch that when it reaches its peak activity. You might be able to shave a few more points off with this method. If this doesn't work, then you are pretty much stuck with what you have unless you want to try adding some amylase enzyme (which in my experience does not work) or beano.

[Ozwald]

2. Oxygen exposure is bad- The yeast are going to mop it up very quickly and fermentation isn't done anyway.

I think it's less about picking up oxygen and more about stirring up yeast (or just knocking CO2 out of solution) that would give you an increase in activity. Oxygen shouldn't be needed for continued fermentation, if limited, it would play a role in growth, but if the existing yeast have crapped out and stopped fermenting, I don't think a need to reproduce is the problem.

Not to mention if the yeast are that crapped out from fermentation, I'd have doubts about how quickly they actually would uptake the O2. You'd still be toeing that cardboard line at best.

My questions for the original post would be what temp was primary? Any temp fluctuations? Was there a raise in temp at the end? Of course these are all pointing towards Boog's suggestion as well, especially after 2 weeks from a 1.083 starting gravity.