Refractometer to measure colostrum quality. The Refractometer should be kept free from any visual dirt. Calibrate the Refractometer using distilled water before each use.  If the scale does not read zero (i.e. at the bottom of the blue section) adjust using the calibration screw

Hold the optical refractometer up to natural light while looking down the eye piece

Always wipe the slide and glass surface clean with a clean soft cloth after a reading.