Originally Posted by EricCSU
Is there a discrepancy with the rest of the recipes or just that one? You should email Greg if there are errors. I bet he would want to know about it.
That's a good question. I checked some of the others and here are the divergences:
13th = 0.6% ABV
9th = 1.3% (1.079->1.010 = 9.1% but they say 7.8%, on an imperial wheat)
8th = 0.1%
7th = 0.6%
6th = .4%
stone smoked porter = 0.3%
stone pale ale = 0.3%
stone levitation = 0.2%
So it's interesting that some recipes have effectively no divergence (<=0.3%), which means that their recipes are consistent with the ABV estimation formula, while other recipes have very high divergence (9th Anniversary, 12th Anniversary, both > 1%).
The FG on the 9th Anniversary is particularly questionable. My guess is the recipe is correct but the FG is overly aggressive. On a 1.079 imperial wheat there's no way my FG would get down to 1.010. It's english ale yeast, and there's no sugar in the recipe. Another odd thing is it calls for a 30 minute mash @148F - so highly attentuative wort, but at 30min you might not even get full conversion. Some other recipes call for 90min mash @148F, which makes more sense.
Maybe I will email him.