refractometer off

I had my refractometer calibrated with RO water. I just bought some solution and checked it and it was off by 2 lines whatever that measurment is I do not know off the top of my head.

I always worry about that because I don't have any solution, just did water too.

scary

I always Calibrate mine with Calibration fluid, you never no whats in the container your putting your RO/DI water in that your using to calibrate your Refractometer, and to make sure you cap your calibration fluid to just after using so you get no evaporation either and use the same eye dropper or what ever your using only on your calibration fluid.