User login

The Secrets of Successful Pad Printing

(February 2003) posted on Wed Mar 12, 2003

This discussion expains how you can make the most of your machine by considering all aspects of production, from climate and press location to substrate readiness and ink preparation.

click an image below to view slideshow

By Carol Swift, Peter Kiddell

Assuming you have all the previous conditions optimized, it's time to turn your attention to optimizing the solvent balance in the ink. Whatever balance you deem to be ideal for the type of inking system you use (open well or sealed cup), this is the balance that must be maintained every time you print.


The only way to achieve consistent and repeatable ink characteristics is to measure ink components by weight when mixing. While some pad-press users mix according to glugs, squirts, or dollups, more precise units should be used--we suggest grams. Only mix as much as you need for the run, because even in a sealed container, the mixed ink will degrade over time. Once you've mixed the ink and added the necessary amount to the machine's inking mechanism, keep the remainder in a sealed container until you need to top off the system.


Maintaining the solvent balance during the run is also vital. In a closed-cup system, this is much easier because solvent has very little opportunity to evaporate from the cup, and, consequently, the ink maintains its printability longer. With an open-cup system, you must establish a standard regimen for solvent addition during production in order to maintain the correct balance in the ink.


Drying the ink

As noted early in this article, pad-printing ink uses fast-drying solvents to support the image-transfer mechanism. Many of the ink systems suitable for the process dry so quickly that it is possible to print wet ink over colors that were printed only moments earlier on multicolor jobs. While the previous colors may not be completely dry, they are dry enough to remain intact on the print surface without affecting subsequent colors.

In spite of these ink characteristics, accelerated drying methods are often used to ensure a dry ink film that will withstand handling soon after printing. The methods vary depending on the ink type used, the substrate being printed, and other application requirements. The most common types of drying systems are radiant heat units (short-wave, medium-wave, and long-wave infrared), hot-air blowers, and flaming systems.



Did you enjoy this article? Click here to subscribe to the magazine.