How to Adjust Pad Printing Ink Viscosity
Viscosity is a fluid’s resistance to flow. Correct ink viscosity in pad printing is critical for filling the plate, transferring the ink to the pad and achieving adhesion on the product surface.
Why are solvent and hardener used?
Controlled solvent evaporation prepares the ink surface for transfer. Hardener helps form a wear-resistant film after printing. Ratios vary by ink series and application, so the manufacturer’s recommendations should always be followed.
How should the ink be prepared?
- Place the mixing cup on a digital scale and tare it.
- Add the required amount of ink.
- Weigh and add the hardener at the ratio specified by the manufacturer.
- Mix until homogeneous.
- Add the appropriate-speed solvent at the recommended ratio.
- Mix again and check the consistency.
The figure-eight test
Use the ink flowing from the mixing stick to draw a figure eight on the surface. If the shape remains clearly visible for a short time before merging back into the mixture, the consistency is suitable as an initial check. For repeatability, weigh every batch and record the formulation.
Note: Temperature and humidity alter the solvent evaporation rate. Climate control in the production area improves printing repeatability.