refractometer calibration

[sphelps]

Originally Posted by rayjay

If you have a seawater refractometer then calibration with water should provide a good reading at normal salt water ranges. However, it is still recommended that one use calibration fluid.
If you have a salt water refractometer (NaCl) which is most common in the hobby, there will be an error at normal salt water ranges if calibrated with water.
Randy Holmes-Farley on Refractometers and Salinity

I was waiting for someone to state they'll be error and post that exact article. This is exactly why I started this thread.

May I ask how much error you would expect and if you've actually tried it yourself?