The Bluelab Calibration Solutions should be a part of every grower's toolbox.
Bluelab’s EC/CF equipment doesn't need calibrating. They're calibrated at Bluelab.
Contamination between solutions can easily occur, which will affect the validity of the calibration. Bluelab recommends that the solutions are de-cantered into a smaller vessel and the contents discarded when the calibration process has been completed.
Learn How to Calibrate your pH Pen