Cleaning solutions are often overlooked but they are an important part of the measuring system. The sensitive pH glass must be clean for an accurate measurement. A build up on the glass will change the measured potential in the solution. This build up can be hard to discern with the naked eye but has an impact on the measurement. If a probe is calibrated when there is a coating and the coating changes in the solution then the calibration is no longer valid and measurements not accurate. It is important to periodically clean the pH electrode to maintain it in the optimal condition.