What is stickiness?

Viscosity is the surface-specific force (ie, a mechanical tension) of the fluid film against splitting. Therefore, stickiness is a measure of how the ink film or coating film will split. The greater the viscosity of an ink, the stronger its adhesion to the printing plate and the blanket (this has a positive effect on the reproduction of details and the opening of the screen), and the stronger its picking tendency. In order to prevent the ink from the previous printing unit from splitting again, if the ink series is not prepared accordingly, the experienced printing union successively reduces its stickiness from the first to the last printing unit, which is a pre-specified color order. the reason. No type of varnish can cause naps because its viscosity is always lower than that of ink. However, if the coating oil adheres more firmly on the coating plate than on the substrate or on the ink film, this is the case when the composite material is printed.

Each ink series has its own individual viscosity temperature ratio. The more viscous, the more heat is dissipated when the ink splits at the nip, and the higher the temperature is needed to work the ink, which in turn affects the viscosity. This dependence is particularly important in waterless offset inks that have a higher viscosity than wet offset inks, but have the same viscosity. In order to maintain the most suitable viscosity range during print production (when the sticky value is inevitably raised from the factory setting), waterless ink requires some form of temperature control in the inking unit. This is why the temperature of the inking device is specified on the ink tank. If it exceeds this temperature, the viscosity will be too high and can cause paste. Therefore, the predetermined temperature range is also referred to as a critical tone temperature (CTT) or a critical lithography index (CTI). Its width can be between 2° and 15°, starting from around 18°C, depending on the manufacturer and application, and ending at 35°C (at a particularly large temperature window).