I recently made an all-grain Russian Imperial Stout on a stovetop, and because of some volume miscalculations (or something), I boiled for 135 minutes to get down to my desired volume of 2.5 gallons. At the end, I discovered that my OG was about 1.115, rather than the expected 1.090, so I added water to get down to my intended OG.
However, after adding 1 package Wyeast ESB wet yeast, and waiting about 3 weeks, the FG is 1.036, which I worry will cause bottle bombs if I go for the bottle.
The fermentation could be stuck or slow (I made another yeast starter and pitched it in a few days ago with no noticeable increase in fermentation), but I wonder whether the long boil produced appreciable non-fermentable sugars, such as melanoidins.
My question is whether a boil this long could produce enough melanoidins (yes, you can taste them!) to increase the FG from an expected 1.010 to 1.036. If so, is there a way to calculate the expected FG based on boil time taking the production on non-fermentables into account?
Also, the brew now has a distinctly smokey flavor. Not terribly burned or anything, and there was no indication that anything burned on the bottom on the boiling pot, but you can definitely taste some smoke in there. I expect it will be sort of pleasant, but I'm just adding this to 1) know why it happened, and 2) perhaps it will help diagnose my high FG.
Hop flavor is good, added bittering close to 60 minutes before the end of boil.