Fisher kel Tath wrote:
Yea...my refractometer has to be off...cause...98% attenuation isn't possible....
Refractometers are not the best instruments to use after fermentation has begun. The alcohol produced throws off the readings and there are some pretty heavy-handed calculations needed to compute to even get close to an actual reading. Even after the calculations, I am not so sure how accurate your results will be.
You are better off taking a true hydrometer reading and adjusting for temperature. Refractometers are best to use pre-fermentation, during lautering (measuring runoff), and during the boil. You could use them during the fermentation, but really only to determine if your fermentation has completed (ie - the readings don't change over the course of several days).