
by Cassandra Balentine
Specific considerations are necessary when printing to various industrial materials, including ceramics and glass. Pretreatments prepare a surface so it’s ideal for laying down ink that offers adhesion, durability, and vibrancy.
Above: 3DT’s plasma systems produce a highly ionized plasma air stream that restructures the chemical properties of materials passed under the treating head and discharge.
Beyond consumer goods like mugs and plates, ceramics and glass are used for items like tiles, furniture, building materials, and even eyeglasses.
However, printing on ceramics and glass provides potential challenges. Sean Lanigan, president, Applied Surface Technologies, LLC, points out that factors impeding the bonding of inks fit broadly into two categories—physical or chemical interference.
“Physical interference can often be described as contaminants. They are things that get onto the surface but can be removed ‘fairly easily.’ Dirt, dust, wax, and oil are typical impediments,” explains Lanigan.
On the other hand, chemical interference is the material itself that makes bonding difficult. In this scenario, things that bond to the surface must be changed, removed, or covered up.
Overall common pretreatment options are plasma, wet chemical—solvents and primers, and flame treatment.
Plasma Treatment
Plasma treatment is a solution used in conjunction with digitally printing on ceramics and glass.
“Solid, liquid, and gas are the three states of matter. However, there is an important, lesser known fourth state of matter, plasma energy, and it’s produced within the surface treatment industry’s plasma treatment systems,” comments Erik Kiel, owner, 3DT LLC.
Bonding problems are pervasive in manufacturing because many materials refuse to bond to other materials as a result of their chemical structure. “Plasma treatment overcomes these manufacturing and decorating challenges by raising the surface tension and functionality of numerous materials,” notes Kiel.
Lanigan sees plasma as generally a better, cleaner, option compared with flame treatment. “It does a better job of removing contaminants and the improved surface tension can last longer than flame treatment. Plasma uses electricity as its power source, so once the equipment is paid for, the cost of operation is low.”
Plasma works well on smaller surfaces that would use a treatment burner of a few inches in width. “The challenge is that as the treatment area increases, the cost of the plasma equipment expands exponentially. Seeing a two- or three-inch plasma treatment unit is quite common, but systems six inches and larger are rarely seen because the cost of equipment is very high,” notes Lanigan.
Kiel points out that the term “atmospheric plasma” is used to describe the technology for plasma treatment performed at atmospheric pressure and does not require placement of products inside of a vacuum chamber.
Atmospheric plasma treatment offers high-volume, inline production since the process is not conducted within a vacuum chamber, which can involve slow and laborious batch processing, adds Kiel.
Atmospheric plasma systems typically utilize an electrical generator and step-up transformer, along with pressurized air, which streams the plasma discharge onto an object via a treating head. Kiel says high-volume, inline production is achieved since the process is not conducted with a vacuum chamber.
3DT’s plasma treatment system, PlasmaDyne Pro, is designed to raise surface tension and improve the functionality of materials.
PlasmaDyne Pro is highly customizable in terms of the number and type of treating heads, programming options, product handling, and automation.
3DT’s PlasmaDyne Pro’s discharge and power are easily adjusted to accommodate various substrates, treating modes, and applications.
3DT has engineered plasma systems for treating glass including exterior glass lighting to improve adhesion of gaskets and housings; automotive glass touch displays for the adhesion of print and coatings; the outside edge of glass windows to improve the adhesion of seals; and eyeglass lenses for improved adhesion of coatings.
Wet Chemical Treatment
Wet chemical treatment options can be cleaners or primers/adhesion promoters. Lanigan says cleaners, washers, wipe down products, and solvent cleaning agents can work for surfaces that are dirty or even have chemical interference; and can increase surface tension.
The advantage of wet chemical treatment is that some cleaners—like glass cleaners, soaps, and some solvents—can be very inexpensive and many don’t require equipment to apply.
Wet chemical primers are available to treat nearly every surface and there are thousands of options. “There are a variety of application methods available from wipe on, to hand and automated spray, and even jettable—printhead applied. Some primers, once applied, can last days or even weeks,” suggests Lanigan.
One wet chemical treatment is Pyrosil, which is a type of combustion chemical vapor deposition. Lanigan explains that Pyrosil burns chemistry in the flame, creating silicon oxide (SiOx), which is deposited onto the surface. “Unlike flame treatment, where the process is a form of heat treatment and temporary, Pyrosil uses the flame as a carrier agent for the SiOx. The SiOx is permanently deposited onto the substrate and creates a highly reactive surface for superior surface tension or wettability.”
One key advantage of Pyrosil is there are a number of equipment choices available, including hand-held, portable units, semi-automated, and fully automated systems.
Lanigan says glass is one of the largest applications for Pyrosil. “In the glass printing industry, when durability is required—abrasion, handling, dishwasher safe, etc.—Pyrosil is the most used pretreatment option.”
Lanigan explains that one reason why Pyrosil has such dominance as a pretreatment in glass decoration is that SiOx and silicon dioxide, which makes up 50-plus percent of glass, share a chemical structural similarity and this creates covalent bonding. “This means that as a pretreatment, Pyrosil easily bonds to and creates a very reactive surface, which is excellent for screen or digital printing.”
For preventing wear and tear on glass objects, which is generally considered scratch, abrasion, and weathering resistance, as well as dishwasher durability, Pyrosil is a chosen product according to Lanigan.
Of course, Kiel admits that working with chemicals can be hazardous to personnel and the environment.
Lanigan sees a number of downsides to using cleaners, which include the cost of labor and finding quality cleaners that work—and work with different materials. “The cost of labor is expensive because most of the cleaning is manual. There are some custom washing systems—like dishwashers, flat glass washing machines, and custom units for many shapes and sizes—but they require a lot of labor or the equipment can be extremely expensive.”
Further, many wet chemical primers have limited durability, or they work on specific substrates. “Almost no primers will work with different materials—plastic, glass, metal, etc. Testing to find a primer that works with a specific application requires many samples, and testing is labor intensive. Most quality primers have a shelf life and can cost more than $1.00 per square foot,” says Lanigan.”
Flame Treatment
Flame treatment is utilized to remove light physical contaminants like dust and increase wettability, for an improved printing surface. “The equipment is relatively inexpensive and the consumables are natural gas or propane, so operating costs are low,” offers Lanigan.
Flame treatment has a few limitations related to adhesion of UV inks. It usually can’t remove heavy physical interference nor can it remove or change most chemical interference from surfaces. The increased surface tension on many substrates like metals and glass can be short lived, and frequently the increase in surface tension isn’t enough for sufficient wettability.
Prepping Glass
Directly printing to glass is useful for a variety of applications, from consumer goods like glassware to industrial applications like tile. Preparing the surface prior to print is an important step. Options include plasma, wet chemical, and flame treatment.
Feb2025, Industrial Print Magazine