pH

pH is the measure of the hydrogen ion content in water. Todays fountain solutions are buffered at 4.0 and do not change if you add more solution. As a press runs the pH will change depending on the compatibility of the ink with the fountain solution. An increase in pH means that the fountain solution is attacking the salts in the ink. If the rise continues unabated, then there will be problems with the plates because the solution is no longer buffered. Most plates are designed to run with fountain solution in a pH range of 3.8 to 4.2. When the pH rises above 4.2, the gum arabic will not adhere properly to the plate and becomes sensitive to ink causing scumming. Thusly, it is important to record pH reading to monitor the relationship of the fountain solution with ink. For quality printing, it is important to maintain the optimum pH for dampening systems.

Conductivity

Conductivity refers to the measure of a material's ability to conduct electricity. As ionic materials are dissolved or go into solution in water, they form ions and the water becomes more conductive. Conductivity increases by about three percent for every degree the temperature rises. Most conductivity meters have built-in temperature compensation. Conductivity doesn't indicate fountain solutions' lithographic properties. Any material that dissolves in water changes conductivity readings. Clays and minerals in paper coatings affect conductivity, as will some soluble salts from ink pigment. Calcium carbonate, which is used in alkaline paper making, can cause problems on press. Calcium ions can react with ions of certain fountain solution chemicals, thus changing the nature of the solution itself and causing the conductivity to change. Calcium also reacts with other materials, forming compounds that can be deposited onto plates, rollers or blankets. In turn, these deposits precipitate glazing, leading to toning in the non-image areas, plate blinding and other problems.