Originally Posted by tnlandsailor
I don't think you can use a refractometer after fermentation has started. I think the alcohol screws up the reading. You can check it against a hydrometer, but I'm pretty sure that is the case.
My only problem with refractometers is, and by all means- correct me if this is irrational, that with such a small sample (basically, one drop), I'm afraid that the margin of error would be really high compared to the larger sample taken for a hydrometer reading. I'm thinking statistically here. A smaller sample means that the whole thing must be completely homogenous to get an accurate representation of the whole. Maybe if you took 3 or 4 readings in a row to see if there is any variation? Just fishing.
my wife bought me one for my birthday today! it's accuracy is + or - 0.20%. it takes 1-2 drops of solution (wort) on the cover slip screen. and you can take a reading after fermentation (according to the little booklet). i hope to test it in a week or two, but i know two pro brewers in Houston that use 'em, and love 'em. according to Northern Brewer, only used for unfermented wort......
but, to each his own. that's the great thing about homebrewing
i take one before i aerate and pitch, and when i keg. i never remeber to when i rack to secondary.