Why Viscosity and pH are Crucial ?
In flexographic printing, print quality and the speed of the press depend on the ink’s characteristics. Generally, solvent-based inks are most popular in flexographic printing. Viscosity and pH of flexographic inks are the two most critical factors determining solvent-based inks’ quality parameters.
Viscosity is the measurement of resistance to the flow of a fluid. Therefore, the ink flow is very important as it decides the runtime of a printing process and the quality of print on the substrate. On the other hand, pH is the measurement of hydrogen ions in the fluid, and it will ascertain whether the fluid in question is acidic or basic.
pH and viscosity are relatable factors and are inversely related. An increase in the pH value of the ink will decrease the viscosity. At the same time, a decrease in the pH value of a solvent-based ink will increase the viscosity of the ink. Therefore, maintaining these two factors within the suitable limits is of sheer importance for the smooth operation of a flexographic printing process.
You can enhance and optimize the productivity of a flexographic printing process only by keeping viscosity and pH factors within the prescribed limits. Many aspects of the flexographic printing process are affected directly by viscosity and pH values, such as ink drying time, quality of the print, ink distribution, color intensity, ink solvent, and printing downtime.
Considering the repercussions of these two factors, one cannot deny the importance of maintaining them for a high-quality printing process. It is a benchmark requirement to control viscosity and pH values in the optimum range to get the best printing results.
How Does Viscosity Affect the Productivity of Flexographic Printing?
Viscosity impacts the characteristics of ink in flexographic printing. Flexographic printing aims to ensure a uniform volume of ink on the substrate. Furthermore, the uniformity of the ink will ensure that you get the desired results in terms of color distribution. All of this depends greatly on the viscosity of the ink.
Viscosity will not only affect the quality parameters of the print but will also increase the cost of printing. Ink solvents are expensive in water-based inks. Therefore, a shift of one second of viscosity in the #2 Zahn cup will increase the ink laydown by 50%. #2 Zahn cup is the viscosity measurement method.
Thus, it is understood that an inconsistent viscosity will require more ink in the flexographic process. Therefore, not only will color management be affected but the ink wastage and cost of printing will also increase considerably. In addition, a high viscosity will increase the downtime of the printing process as the ink will move slowly in the transfer from anilox rolls onto the printing plate.
Moreover, the ink will dry quickly when the viscosity is high. Therefore, it may cause ink clogging at several points within flexographic printing. Resultantly, it may cause printing jams and slow the whole process. On the other hand, lower viscosity will affect the print quality severely. It will distort the color scheme, and the colors will appear lighter. Furthermore, the ink will take a lot of time to dry.
Hence, the viscosity will impact the printing process in several ways. The best solution is to keep the viscosity within limits for a seamless printing process. Typically, adding more solvent to the ink is advisable when the viscosity is low. Ideally, the viscosity of a run should remain consistent and may not exceed +/-5%. Automated viscometers are installed with the printing machine that determines the real-time viscosity of ink and will help to control it accordingly. In addition, viscosity maintenance will save ink solvent by up to 60%.
How Does pH Value Affect the Productivity ?
Monitoring ink’s pH value is of great importance as it correlates with the viscosity factor. pH value has an indirect relation with the viscosity factor. If you increase the ink’s pH value, the ink’s viscosity will decrease. Thereby, the drying time of the ink increases, and it will have print quality problems.
Conversely, the lower pH value will increase the ink’s viscosity. As we have seen earlier, the higher viscosity of ink will decrease the drying time, and you may face ink clogging issues in the printing process. Furthermore, ink clogging can lead to print jamming; thus, the printing downtime will increase.
Hence, the best practice is to manage and balance pH values and viscosity so that both are in ideal ranges and do not hinder the printing process. Ph will directly impact the quality and speed of the printing press. Therefore, constantly check the pH value and use the value per the prescribed requirements to get the best results without significantly impacting the viscosity factor.
If you want to lower the pH of the ink, add water to it. On the hand, you should add solvent if you want to increase the pH value. You must change (increase or decrease) the pH value per the requirements by using the described methodology.
What Should Be Viscosity And pH Values for Increasing Productivity?
Ink is a crucial component of a flexographic printing process. The properties of ink effects a lot of factors within the printing process. Viscosity and pH values are the two factors that determine the quality of ink and the printing process in general.
The importance of viscosity and pH values is undeniable. The viscosity of the ink in the #2 Zahn cup should be in the range of 19-24 seconds to increase the productivity of the flexographic printing. On the contrary, the pH value should be between 8.2 and 9.4. The flexographic printing process will go on seamlessly without ink wastage and excessive printing downtime if you monitor and manage these two factors in the optimum range.
Final Thoughts
Viscosity and pH values are the two factors that impact the ink of the printing process markedly. Ink, the chief component of the flexographic printing process, will play a decisive role in print quality and press speed. Hence, it is crucial to managing the values of viscosity and pH of ink to enhance the productivity of the printing process.
Any extreme values of viscosity or pH will affect the quality of print and the printing downtime. Therefore, it is advisable to keep viscosity between 19 and 24 seconds for best results. In comparison, the ideal pH value of ink should range from 8.2 to 9.4.
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