Calibration fluid question

[Pescador]

From Reef Central

Over on the chemistry forum the consensus is that refractometers should be calibrated with a solution that has a salinity close to that of natural sea water. A lot of people are finding out that even though they calibrated their refractometer with distilled water, when they tested a calibration fluid their measurements were way off.

I'm one of those people. I've been calibrating my refractometer with distilled water since I got it. After reading those posts, I recalibrated it with a calibrating solution. My refractometer was off by 0.005. My reef's actual salinity was 1.021 when I thought it was 1.026. Quite a big difference.

That being said, Randy has written an article detailing how to make your own calibration solution using distilled water and table salt.

Pinpoint Salinity Calibration Fluid

[tlo]

although it is said to be better to use calibration fluid, I find it hard to come by (maybe its just my area) so I use ro/di as well. IF it was readily accessible to me, I would be using it though.