by Cassandra Balentine
Part two of three
There are several misconceptions about pretreatment for digital, direct to object (DTO) glass printing.
One is that if the print looks good straight off the machine, the job is done. “Initial appearance is not the same as long-term adhesion. A print can look perfectly acceptable and still fail later in use. Another misconception is that one pretreatment method will work for every type of glass. That is rarely the case. This is a testing-led process, and the right answer depends on the final application. There is also a misconception that digital printing has somehow removed the need for pretreatment. It has not. In many cases, pretreatment is still fundamental to achieving a production-ready result,” exclaims Ken Tyler, national sales manger, Engineered Printing Solutions.
Another is that once you pretreat a substrate, that it is good to print forever. “Surface contaminants can be reintroduced to a substrate based on the print environment. A dusty or dirty shop can lead to poor adhesion results. It is still ideal to print soon after pretreatment,” notes Sandi Baginski, creative director, Innovative Digital Systems (IDS).
Pretreatment can sometimes be thought of as a standalone step, but Tom Lang, digital product manager, Inkcups, says in reality, the overall print durability on glass depends on the ink used, the curing, and the type of glass coating. “This means it’s important that pretreatment is matched to the application to achieve the desired end result. This misconception means that pretreatment can be thought of as optional, or that simply cleaning the glass is sufficient.”
While cleaning alone removes surface contaminants, it does not increase surface energy or create the conditions required for durable ink adhesion. Lang says this is because each pretreatment method delivers a different abrasion resistance, the key here is to think about the desired abrasion resistance for the end use and pick the pretreatment most well suited to this outcome.
Other misconceptions are all primers and methods are alike and work for every substrate. “Some methods work for different surfaces but there is not one primer that works for all. Each substrate may require a different form of pretreatment—whether flame, corona, plasma, a primer, or a combination of methods. The appropriate approach depends on the surface tension of the material,” says Lang.
Tips and Tricks
Before investing in digital DTO equipment for glass printing, Lang says it’s important to consider what your desired applications are, as this will determine the most suitable technology. For example, what are your desired run lengths, design complexity, durability requirements, range of typical part sizes, and how many different types of glass will be being decorated?
Cylindrical DTO UV digital inkjet systems are well suited to short runs, on demand production, and 360-degree decoration with vibrant colors, tactile effects, and variable data. “However, it’s also critical to evaluate pretreatment requirements as adhesion and durability will depend on selecting the right method for each application,” says Lang.
Viewing the decision holistically and matching the printer, ink, and pretreatment system to your desired application is the best way to achieve high quality prints on glass that last adds Lang.
Some companies offer test treatment of glass substrates for potential customers to check adhesion improvement after pretreatment, shares Dr. Arnd Schimanski, managing director, SURA Instruments GmbH.
It it important to review the process from beginning to the end and define test methods. Bas Buser, global segment manager printing applications, Plasmatreat GmbH, shares that this is helpful in testing on forehand and during later production and provides quality assurance.
Baginski stresses that the most important advice is to test with real production parts—not sample glass that may not reflect actual coatings or treatments. Other best practices include define durability expectations early, test adhesion using real-world conditions, evaluate the full workflow, not just the printer, standardize cleaning and handling procedures, and work with experienced partners who understand application requirements. “The most successful implementations focus on having the right technology in place for the job at hand and building a repeatable process.”
Tyler suggests the most important advice is to test real parts, not just generic samples. “If a company is evaluating digital printing on glass, they should send the actual production substrate to the supplier they are considering and ask them to print it using the equipment being proposed. Ideally, they should also visit and see the machine running in person. Glass can be challenging, particularly on cylindrical packaging, and success depends on much more than the print engine alone. Pretreatment, curing, part tolerances, and handling all influence the final result. It is important to evaluate the full process before making a capital investment.”
Jun2026, Industrial Print Magazine
