What is the viscosity of water-based ink?
Date: Jul 26 2024 From: Star Color
The viscosity of water-based ink is a term used to describe its fluidity. The higher the viscosity, the harder it is to flow, and the lower the viscosity, the easier it is to flow. A more professional term refers to the measurement of the ability of molecules in a fluid to slow down or reduce their intermolecular motion due to interactions. It is an important physical characteristic of water-based ink, which directly affects the printing effect and application performance of the ink. The following is a detailed explanation of the viscosity of water-based ink:
1、 Definition of viscosity
Viscosity is a characteristic that measures the relative flow obstruction within a fluid, reflecting the ease of fluid flow. In water-based ink, the viscosity determines the fluidity and transferability of the ink during the printing process. Various printing methods have different requirements for the viscosity of ink. For example, the viscosity of flexographic printing ink cannot be too high and needs to have good fluidity, while the viscosity of screen printing ink is relatively high.
2、 The influence of viscosity on printing
Ink transfer performance: Ink with appropriate viscosity can better transfer from the ink supply system of the printing machine to the substrate, ensuring uniform and full ink color of the printed product. Low viscosity can cause excessive diffusion of ink during transfer, resulting in significant dot expansion and deformation of high gloss dots; If the viscosity is too high, it will make it difficult for the ink to transfer, which can easily lead to uneven ink color, insufficient color printing, and problems such as dirty and paste printing.
Printing speed: Ink with appropriate viscosity helps maintain stable printing speed. Ink with high viscosity has poor fluidity and may reduce printing speed; Ink with low viscosity may have difficulty controlling printing quality due to rapid transfer.
Printing stability: Ink with stable viscosity helps maintain the consistency of printed materials. During the long-term continuous printing process, the change in ink viscosity will directly affect the quality stability of the printed product.
3、 Factors affecting viscosity
Temperature: Temperature is an important factor affecting the viscosity of water-based ink. As the temperature increases, the movement of water molecules accelerates, and the evaporation rate of solvents in the ink increases, resulting in a decrease in viscosity. On the contrary, when the temperature decreases, the solvent evaporation rate slows down and the viscosity increases. Therefore, it is necessary to control the workshop temperature during the printing process to ensure the stability of ink viscosity.
PH value: The pH value of water-based ink also has a certain impact on its viscosity. Generally speaking, when the pH value is within the range of 8.5-9.5, water-based ink has the best printing performance and relatively stable viscosity. When the pH value deviates from this range, the viscosity of the ink may change, thereby affecting the printing effect.
Ink components: The components of water-based ink include organic pigments, binders (mainly composed of resin and water), solvents, and related additives. The type, content, and properties of these components will affect the viscosity of the ink.
Thixotropy: Thixotropy refers to the property of ink that increases in fluidity under external stirring, gradually decreases in fluidity after stopping stirring, and returns to its original state. Ink with good thixotropy can better adapt to different printing speeds and pressure changes during the printing process, maintaining stable viscosity.
4、 Measurement and adjustment of viscosity
Measurement method: The viscosity of water-based ink can be measured by various methods, such as using a No.4 cup viscometer or a Chaen cup (viscosity cup). Temperature and other conditions need to be controlled during the measurement process to ensure the accuracy of the measurement results.
Adjustment method: When the viscosity of water-based ink is not suitable, it can be adjusted by adding diluents (such as water or a mixture of water and ethanol), stabilizers, or adjusting the temperature. During the adjustment process, it is important to maintain a stable pH value of the ink to avoid any adverse effects on the printing effect.
Our Huizhou StarColor produces flexographic water-based ink using a high concentration, low viscosity method. During the printing process, no additional adjustments are required and it can be used on the machine. For more questions about the use of water-based ink, please visit our website: www.starcolorink.com
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