Conductivity + PH = Compatibility Conductivity Leads to Compatibility and Performance Enhancement Introduction: Now that we have looked at PH of the solution, it is time to look at Conductivity of solution as it applies to performance on press and in the print quality of the finished printed piece. I. Conductivity defined The ability of water or a solution to pass electric current. This ability depends on the movement of ions (dissolved species caring an electrical charge) in the fountain solution. Generally, therefore the greater the number of ions of a specific type in a solution, the greater will be its conductivity. While there are some impurities in the water itself, and they are referred to as total dissolved solids (TDS). The overall conductivity is the measurement of active ions in the fountain solution, that are working for you. What to look for when mixing fountain solution A. Take a sample of the tap H2O and get a reading of the conductivity at room temperature. II. Take a reading from the bottle of foundation solution concentrate and make a note of that, since chemicals can be damaged in shipping by temperature changes. III. Make a chart showing the concentration changes of 1/2 ounce to 1 ounce of etch added to the gallon of H2O When using alcohol or alcohol substitutes make a note of any changes in conductivity. Alcohol and most alcohol substitutes are non-conductors and will cause a drop in conductivity. Now at this stage of quality control these numbers of conductivity and pH will be documented as your control levels. In general, approximately 250 micromohs to 400 micromohs is considered normal tap H2O. Below 250 is soft water and above 400 is considered hard water. Hard water will tend to have more of a foaming activity in the water tank, thus requiring some added buffering agents to combat the unwanted ions. A. PH-meter: determines the concentration of ions present. B. Conductivity meter: determines the activity content of the ions IV. At standard room temperatures of 70 to 75 degrees Fahrenheit, water by itself, has a low electrical conductivity, which indicates that there is some disassociation into ions.   Conductivity is a measure of the ability of a given substance to conduct electric current equal to the reciprocal of the resistance of the substance. I.E. fountain solutions. The conductivity of an ionic solution depends on the number and type of ions present and, therefore, varies with their concentrations. A. Tap water vs. DI water: When mixing fountain solution. B. The conductivity of a ionic solution depends also on the temperature of the solution. C. On press conductivity is related to the resistance of a solution to be compatible with the ink. Monitoring of the conductivity can often usefully indicate variations in salt concentrations in water solution. Water is the reciprocal of conductivity. The more pure the water the better reciprocal of conductivity the water will be and the better control of tap water, fountain solution, plate, ink and paper interaction. Conductivity is your tool to tell how much etch is being used. Why is the measure of conductivity so important A.   Measuring conductivity is the best way to identify how buffered your fountain solution is, when working towards controlling the press compatibility of the fountain solutions and printing ink quality. What can effect conductivity performance on press and what to check. A. Changes in conductivity as low as 100 to 200 micromohs is significant to quality of performance, when teetering on the edge of compatibility. B. Old ink that was dug out of the ink fountain, and put back into the can and then re-used again, this ink is contaminated, use fresh ink. If the press operator is working with established known recorded numbers of pH, conductivity, and performance of press, is varying then these steps will help track down the area of concern. A. Check and make sure your water tray's and recirculation tanks are clean. Fresh fountain solution keeps the values of your control zones, close to the starting point. B. Check the compatibility of ink and fountain solution together. There are many combinations to try to achieve better levels of compatibility performance. C. Check roller strip setting and roller durometers. If there is no roller durometer gauge available at your printing plant, simply call your roller manufactures representative and ask them to come and give you a reading of your durometers. This is a free service. Conclusion: There are no magic numbers. Do to the increase quality and speed of delivering printing jobs in today's world arena it is so very important that composition of your fountain solution is strictly controlled. PH and conductivity working together in the press environment will greatly enhance your progress towards the ultimate compatibility of chemistry on press. Press operators must remember that the ideal numbers need to be found, through testing your own specific needs. When you achieve the balance between tap water, fountain solution, and ink, your desired results will be predicable. Maintaining the balance is quality control for your pressroom environment. Tip: Standardizing for a starting point, is a conductivity of 1500 to 2200 with a PH of 4.00 to 5.50 depending on press, dampening system, and plate type. For technical support on these topics or others, contact us via email at SpeedyDry technical support or call 1.866.808.9908