Be sure to remove the rubber protective layer and clean it regularly. The crystal must be kept clean too. You can use alcohol swabs for this purpose, or isopropyl alcohol. If you can’t obtain these products, deionised water should be sufficient. Avoid any abrasive material, though the crystal is super tough so it won’t be scratched by a paper towel.
We recommend you keep your cleaning solution, calibration water and the coffee refractometer together in the same environment so they will always be at the same temperature. Temperature equilibrium is key to taking accurate readings.
To calibrate the VST Refractometer Lab 1,2 or 3, add 0.5g of deionised water to the crystal, then simply press menu twice. Press enter when prompted to ‘set zero’ and the device will again read pure water as zero TDS.
Is it Waterproof?
The refractometer is water resistant but we recommend against immersing it. When you replace the batteries, you will notice a rubber compression seal which, if it is not seated correctly, can allow water to enter the device; care should be taken to re-assemble the device properly.
This video gives specific instructions on cleaning and calibrating the Coffee Refractometer