By Dave Foster
The hand held refractometer is commonly used to check coolant concentration, based upon the refractive index of the coolant solution. The most important thing to remember when using a refractometer is that they read on a Brix scale not actual percentages. To get actual percent of the coolant concentration you must multiply the refractometer reading by the coolants refractive index multiplier which can be found on the tech data sheets. For example, CommCool XP has a refractive index of 1.60, and you currently see 5 on your refractometer, the coolant concentration would be 1.6 x 5 = 8%, slightly on the high side.


• Calibrate your refractometer each time you use it  by placing a drop of shop water onto the prism and lower the cover plate. It should read zero. If not, adjust the set screw.
• After wiping the prism clean, place a few drops of coolant onto the prism. Try to take the coolant from the coolant nozzle and not from the coolant sump. Close the cover and read.
• Refer to coolant specifications for correct reading.
• Keep in mind that tramp oil will blur the line on the refractometer.
• Remember that this is an optical instrument and should not be dropped or handled roughly