How fragile are refractometers?

A couple years back, I bought a refractometer to allow me to measure the gravity of my small (1 gallon) batches without losing a non-trivial amount of wort/beer to the measurement itself. I much prefer being able to get my gravity with just a couple of drops than an entire sample tube.

However, a couple of weeks ago, I brewed with a pro brewer who told me that refractometers are extremely sensitive and fragile, and that merely placing it down on the table can mess up its reading. I've never been particularly rough with mine, but I haven't babied it either. Now I'm worried about the accuracy of the readings I'm getting.

Last weekend, I brewed a porter. I checked my pre-boil gravity with a refractometer, and it indicated 1.015. Panicked, I grabbed my hydrometer, pulled a sample in my sample tube, cooled it in a pitcher of cold water for half an hour, and measured again. This time it came in at 1.045, much more reasonable.

Now I don't know if I can trust my refractometer. What is everyone else's experience with this instrument?

Just calibrate it with distiller water

There's a screw on top to adjust it to a known value, e.g. water.

I haven't been off more than a couple of points from expected OG. I check the calibration on mine with distilled water before each brew session and it usually doesn't need much for an adjustment.

That's way off! Maybe something got loose inside? It didn't get wet or soaked, did it?

Calibrate with (distilled) water and verify correctness with a known Brix solution, using a hydrometer as reference.

I don't know where your pro brewer got his information from, they are not that fragile or sensitive to handling. They are finicky about temperature, but that's where the ATC comes in.

Did you take multiple readings? I usually take a few rom different parts of the kettle. Sometimes you'll get layering in the wort that will give you bad readings. Usually giving the wort a stir before taking readings helps.

The only time I've gotten really bad readings was when the refractometer got really cold (like 5F).

I use refractometers exclusively, and never found them to be particularly sensitive. My readings are very consistent. I definitely agree with the layering theory. Keep in mind that the FG readings are NOT accurate. There are correction procedures for FG, but even going through all that, I put little stock in the actual reading. I know about what to expect for an FG reading for a given OG, but if you really want accurate readings of FG, you need to resort to a hydrometer...........

H.W.

I just use the calculators for FG. They're close enough for me.