Og

[Sean]

In the BYO 150 clones mag, on page 29 is Rogue IPA. It calls for 16.25lb of pale malt as the only grain, and a final gravity of 1.020, at ABV 7.8%.

My question is: is it the yeast that stops that fermentation? otherwise I would think it would ferment down to 1.010 or so.

so I'm looking at it from a recipe building perspective. This must be a 'planned stop' ?? In order to leave residual sugar?

Please reference any reading material.
Thanks

 

[MrSaLTy]

Your final gravity depends on the attenuation of the yeast you use and the amount of unfermentable sugar in the wort. If for example, you had a starting gravity of 1.100 and your yeast had a stated attenuation of 80% it SHOULD end around 1.020 assuming there was no sugars that are unfermentable and everything was perfect. The attenuation is usually given in a range though like 70-80% . Some yeasts like WPL002 are only about 63% attenuative. If you started at a 1.100 gravity and used that yeast you would end up probably around 1.030-1.040 Its going to vary all the time depending on these things and that is why you can only GUESS what the final gravity will be but there is no certainty.