FAQs
What factors influence the drying rate and rub resistance of ink in the printing process?
Ink drying speed and rub resistance are influenced by the substrate you are printing on, the type of press you are using, the ink volume and the ink formulation.
If you are printing on an absorbent substrate, such as Kraft or White Top, the ink will absorb into the liner versus printing on a coated liner where the ink sits on top. When printing on absorbent substrates, the ink will dry faster and have more rub than when printing on coated substrates.
The amount of volume you put down also influences the drying speed and rub resistance. For example, if you have a 400 lpi 3.7 bcmpsi anilox roll and a 250 lpi 5.8 bcmpsi, the ink running on the 3.7 bcmpsi will dry faster on a given substrate simply because of volume. Press conditions such as vacuum transfer or dryers, etc. also influence the drying speed.
With regards to ink formulation, the main ingredients that influence the drying speed of water based inks are the types of resins used during formulation. Some resins are film-formers while others are brittle. Your ink manufacturer should formulate inks with the type of resins that best fit your application and press. For example, if you have vacuum transfer, you may need slower drying, more resoluble ink than if you have a press that does not have vacuum transfer. Also, pH has a major influence on ink drying speed. When the amines (ammonia or MEA) evaporate while on press, the pH decreases and causes the drying speed to increase, viscosity to increase and the ink to become less resoluble. This is why it is important to maintain your ideal pH level. Ink additives that may be added press-side, such as glycol, can also influence an ink drying speed.
The type of resin used to formulate ink will also have a strong influence on rub resistance. Fillers such as Calcium Carbonate can increase the likelihood that ink is going to rub. Press-side additives such as wax are sometimes added to decrease the amount of rub.
