How to use a refractometer

JUNE 2021

Overview

The concentration of a coolant, cleaner or other aqueous solution is usually determined in the field with the use of a handheld refractometer.  The range of the refractometer must cover that expected by the diluted solution.  If the dilute solution is too concentrated for the refractometer that is being used a further dilution of the fluid can be made and the appropriate factors applied.

Equipment

• 0-16 or 0-32 range (Brix) handheld refractometer
• Clean tap or distilled water
• Clean Lint Free Tissue
• Dropper Pipette

Refractometer Brix scale

Simplified Measurement Method

1. Using a dropper pipette, transfer one or two drops of room temperature water to the prism (clear glass) of the refractometer and close the cover plate.  The sample must spread all over the prism surface.
2. Look at the scale through the eyepiece and read the scale where the boundary line intercepts it.
3. Set the boundary line to read zero by using the adjusting screw for calibration.
4. Wipe the prism clean with a clean lint free tissue.
5. Using a dropper pipette, transfer one or two drops of the system coolant sump to the prism (clear glass) of the refractometer and close the cover plate.  The sample must spread all over the prism surface.  Do not dip the refractometer into the coolant sump. Do not place the refractometer under a coolant stream.  Not following these directions can damage the refractometer prism and calibration.
6. Look at the scale through the eyepiece and read the scale where the boundary line intercepts it.
7. Wipe the prism clean with a clean lint free tissue and water.

Concentration Control

Use of a 0 to 10 or a 0 to 32 refractometer is suggested to manage coolant concentration.  Use the control chart for the coolant in question to determine the appropriate refractometer reading for the concentration that you desire.  If a coolant control chart is not available use the refractometer factor to determine the concentration of the fluid.  If not factor or control chart are available contact your sales representative on how to determine your coolant concentration.