Pre-measured refractometer calibration solution takes the guesswork out of properly calibrating your instrument - with no need for expensive or unreliable measuring equipment. A refractometer is essential to the saltwater hobbyist for success. Maintain its accuracy by recalibrating regularly. Shake bottle well before application. Ensure the refractometer prism surface is clean, wipe with distilled or RO water if necessary and dry with a cloth. Add 2 - 3 drops of solution to the prism surface and cover. Adjust calibration mechanism to read to one of the following specifications: 35 ppt 1.0264 Specific Gravity at 25 deg C 1.3394 Refractive Index 53 mS/cm at 25 deg C Clean and dry prism surface after use. Check instrument calibration regularly, once per month is recommended. Do not add test fluid back to container. Tightly replace lid to prevent evaporation. Note: If using an ATC Refractometer, allow 45 seconds before reading.
