When I want to take a gravity reading during a brew day, I will typically dip it out with a tablespoon from the kettle, set the spoon on a bowl for a few minutes to let any particulates settle, then draw a clear sample from the edge of the spoon with a dropper.
I was taking readings at various times during a recent brew day and found my gravity numbers were all quite far above what I expected. Great, though I, free gravity! Must have crushed a bit tighter today or something.
When I was all done, however, I measured a post-chill sample with both the refract and a hydrometer and found my gravity right where I had originally calculated it! I didn't get free points, it was right at my usual 75% efficiency!
I wonder now if I was getting evaporation in the spoon samples that is fast enough to skew the readings. Perhaps I need to be taking a larger sample, or measuring it sooner. Another variable might be the weather - this is the first time I've brewed this year since the weather cooled off, so instead of 90F and high humidity, I had 60F and dry breezes.
Anyway, if anyone has any suggestions on better techniques for using a refractometer, I'd love to hear them!
