For someone with a Masters Degree thats not a very good experiment. Why only one refractometer? There are many brands of different cost and quality. I've seen them range from $12 to $197 on ebay. Where is his control group? Where are the references? Where are the details period? When read with the Steven Pro article provided in the link the only idea that it seems to support is that cheep well used hobby grade equipment doesnt last.
Randy Holmes Farley PhD writes a much better article on the subject: Refractometers and Salinity Measurement
http://www.reefkeeping.com/issues/20...f/index.php#12
I've owned my Refractometer (the brand J&L sells) for 3 years. After 2 years I calibrated it with a solution of known salinity for the first time and it was low by 0.001