Refractometer

[kattsue]

Why distilled water on daylight plate before using. does it have to be distilled water?

 

[Jefe12234]

It has to be calibrated to give accurate results. And really, it should be calibrated using a 35ppt salinity standard. I calibrated mine with RO/DI and found it to be reading 3ppt high after calibrating with the salinity standard. Many others have reported the same. Salinity standards are usually sold as calibration solutions for conductivity meters. The Pinpoint solution can be used for refractometers and should be pretty easy to find.