UV Printing on Glass: First Surface, Second Surface, White Ink and When Frit Is Right
Reverse print, white ink, frosting and lamination, the full specification checklist for architectural glass.
UV printing on glass puts artwork straight onto a flat glass panel with UV-curable ink, cured by UV light as the printhead passes, so there is no film or sticker to lift. The print can go on the face you touch (first surface) or on the back, mirrored, so it is read through the glass (second surface, also called reverse printing). Colour on clear glass reads as a tint unless white ink is printed behind it. Printing comes last, after the glass is cut, drilled and toughened, and it suits interior and protected glass; façade and spandrel glass is normally specified as fired ceramic frit, which the glass processor fuses in during tempering.
This guide explains each of those choices in plain English. What we can print, what to send and how to get a quote are on our glass printing in Dubai service page, and panel specification, coated glass and artwork across several panels are in our large format glass printing guide.
Defining UV Printing on Glass in Dubai: What the Process Involves
UV printing on glass is a digital process. The printer jets ink onto the glass and UV-LED lamps cure it as the head passes. The cured ink forms a layer on the surface of the glass. It is not fused into the glass, as fired ceramic frit is, which is why UV printing suits interior glass and glass protected from the weather. How long that layer lasts depends on the glass, the primer, the cure and where the panel is fitted.
Curing turns the liquid ink into a solid film. The UV light sets off a chemical reaction in the ink (photopolymerisation) that completes in milliseconds. LED lamps run much cooler than the mercury lamps of older printers, so the glass and any coating on it take little heat. The inks set under light rather than by a solvent evaporating, so solvent emissions while printing are lower than with solvent-based printing. That is not the same as zero, and each ink’s safety data sheet sets out what it contains.
Before digital UV printing, graphics on glass were mostly vinyl film or screen print. Vinyl can bubble or peel over time in the UAE’s heat and humidity. Screen printing is durable, but every design needs its own screen, which makes short runs and one-off panels expensive. A UV print needs neither film nor screen, and it holds well when the glass is cleaned and primed correctly before printing.
Print Detail, White Ink and Raised Print
Fine detail on glass comes down to where each droplet of ink lands. The printheads place very small droplets in exact positions, which matters on glass because light passing through the panel shows up any unevenness in the print. We use UV-curable inks and check adhesion by testing on the actual panel.
On clear or tinted glass, CMYK inks are translucent, so colour needs a dense white layer behind it to read as boldly as it would on a white wall. On a front (first surface) print the white goes down first, under the colour. On a reverse (second surface) print it goes down last, over the colour, so it still backs the colour from the viewer’s side. The white is there for opacity, not adhesion. Adhesion is the primer’s job, and the primer goes down before any ink. Printing the white only where it is wanted gives selective opacity: one pane can carry fully opaque logos beside semi-transparent gradients, or a frosted, sandblast look without acid etching, so a partition gives privacy where it is needed and stays clear elsewhere.
UV ink can also be built up in layers, printed in exact register, so the print has physical height on the face of the glass: a raised texture you can feel. How raised and tactile print is built is covered in our guide to raised and tactile UV printing.
What is reverse printing on glass?
Reverse printing, also called second surface printing, means printing on the back face of the glass so the artwork is read through it. Compared with a print on the front, three things change.
The artwork is mirrored. Tell us which face is the viewing side before files are set up, so the image reads the right way round through the glass.
The layer order reverses. On the front, white goes down first and the colour on top. On the back, the colour goes down first and the white is laid over it, so it still backs the colour from the viewer’s side.
The glass protects the print from wear. Cleaning cloths, hands and hot cups only ever touch bare glass, and the thickness of the pane gives the image depth and gloss. It does little against strong sun, though.
A first surface print suits panels fixed against a wall, where the back of the glass is never seen, and it is the only option for raised or tactile print, which has to be on the face people touch. A reverse print suits splashbacks, tabletops and partitions that are cleaned every day. Our reverse printed glass splashbacks for a Dubai hotel apartment development show the technique across a large run, and the same method on clear acrylic is explained in how acrylic printing works.
Applications: Partitions, Cafés, Splashbacks and Colour-Matched Sets
Printed partitions divide an office without closing it off. For the meeting room glass at PRO TECHnology, part of our own group, we printed a pattern across the six panels that enclose the room, each 2.4 metres tall and 1 metre wide, with coverage set to break sightlines while the partition still reads as glass. The printed glass in a managing director’s office is five panels, each 3 metres tall and 1 metre wide, with a geometric pattern in layered colour that has to work backlit by the sun during the day and lit from inside the room at night.
Cafés and restaurants put printed glass on surfaces that are cleaned all day. For McDonald’s we printed the brand palette onto tempered glass as large-format interior features in a flagship restaurant, with the cleaning regime and its chemicals treated as part of the specification. For Segafredo Zanetti, one family of artwork runs across printed glass walls and tabletops in its cafés, so the walls and the tables read as one interior.
Kitchen splashbacks and bathroom panels are printed on the back face, so the cloth meets bare glass and the ink sits behind it. The hotel apartment splashbacks mentioned above were printed that way, in flat single colours repeated across the unit types, with the socket and switch cut-outs made at the glazier before the panels reached us.
Where several panels are seen together, the colour has to match from one panel to the next. For the light blue colour-matched glass panels at The Dubai Mall, the client supplied plain glass, already cut and with its holes made. We UV printed one light blue across multiple large-format panels, and the client collected and installed them.
Adhesion, Cleaning and Sun: How Printed Glass Holds Up
The usual worry is that the ink will scratch, peel or lift off the smooth glass. Whether it does depends on the bond between the ink and the glass. Done properly, the primer chemically couples the cured ink to the surface, so the ink is not simply resting on it. It is still a coating on the glass, not a layer fused into it.
That bond comes from the pre-treatment. The glass is cleaned, then a primer is applied that bridges the inorganic glass surface and the organic ink. Our guide to UV ink adhesion and pre-treatment explains why a print peels when a step is skipped.
Cleaning is simple: soft, non-abrasive cloths and mild, pH-neutral cleaners. Avoid strong solvents and abrasive pads, which can wear the surface of the ink over time.
Sun is the harder test. The lightfastness of UV ink is finite and depends on the ink, the cure and the exposure, so it suits internal partitions and protected glazing. Fully exposed façades are a different question: organic UV ink is a surface coating, while fired ceramic frit (glass powder and inorganic pigment fused into the panel at tempering temperature, covered by ASTM C1048 Condition B) is what is normally specified for façade and spandrel work. The two are not equivalent, and we will say which one a job needs.
Indoors, a fully cured print holds up well in a busy shop or a home bathroom. How long it keeps its colour depends on the ink, the cure, the cleaning it gets and how much direct sun reaches it, and we cover each of those in how long UV printing lasts.
Direct-to-Surface Printing at Sun Studio Dubai
Sun Studio LLC has printed direct onto surfaces in Al Quoz, Dubai, since 2011, for customers in all seven emirates. Flat glass is printed on our flatbed UV printers, including the Direct Color Systems UV84 and the IQDEMY EVO 2500, a belt flatbed 2.5 metres wide with no machine limit on length, which we use for large glass panels; bottles and other round glass go on the LSINC cylindrical presses and have their own pages. Sun Studio belongs to the same Dubai group as PRO TECHnology, which distributes Direct Color Systems, IQDEMY and LSINC equipment in the Middle East, so read our view of the machines with that in mind. Where the glass is unknown, coated or heading somewhere demanding, we print a sample on your own glass before a panel schedule is committed, because the specific panel, not glass as a category, decides how well the ink holds.
