Testing Listed Antifreeze with a Refractometer
The following guidelines are generally applicable, but always follow the refractometer manufacturer’s and listed antifreeze manufacturer’s instructions.
You’ll need:
- A container to hold drained antifreeze for testing
- Thermometer
- Unused droppers or pipettes
- Installation manual for the listed antifreeze brand
- Refractometer
Basic steps to test listed antifreeze with a refractometer:
- Clean and dry your refractometer before use. Residual antifreeze or water will change the results. Rinse the well with deionized or distilled water as tap water has variable quality that can affect readings.
- Inspect the pipes and hang tag.
- Shut off the water source and drain a half gallon of antifreeze from the most remote part of the system. You may need to pull multiple samples if the system is large and covers areas with stark temperature differences.
- Calibrate the device in the testing environment to bring both the device and the testing fluid to about the same ambient temperature.
- Use a dropper or pipette to add listed antifreeze to be tested into the well, ensuring that the sight glass is covered.
- If the sample tests in specification, replace the drained antifreeze and update the hang tag.
- If the sample tests out of specification, follow NFPA standards for a full system drain, flush and replacement.
The RI will be reported as a unitless number at a particular temperature, or autocorrected to 20ºC, often shown as “nD20”. The refractive index is always reported at a particular temperature because RI changes with temperature. The colder your antifreeze is when measured, the higher the RI, and vice versa.
Listed antifreeze, like freezemaster™ antifreeze, is never to be purposely diluted with water. Diluted listed antifreeze is considered out of specification and must be drained and replaced. The chart below shows the freeze point and RI of freezemaster™ antifreeze as diluted with water at varying percentages and measured with a laboratory-grade Abbe refractometer at 20ºC. The corresponding freezing points (ASTM D6660 method) are also shown below.
