Printing on Ceramic Tiles
Some of you may remember that I had a house fire almost a year ago. We are now in the rebuilding stage: more precisely at the “choosing tile for the bathrooms” phase. Wow. I have been blown away by the varieties of printed ceramic tile. This has sent me to the Internet, and what I have found has banished from my mind any question of the death of printing.
How They Have Printed Tiles for Centuries
From my research, it seems that screen printing was the method of choice. That makes sense, since this process can print a huge number of tiles cheaply. Either flatbed screen printing or rotary screen printing was employed.
To explain, flatbed screen printing involves a series of stretched screens with patterns blocked out (or left clear). When the press operator draws a rubber squeegie across the inked screen, he/she forces ink through the open mesh. Where the screen has been blocked (with a physically applied or photographically produced blockout), no ink gets through.
A rotary screen press works in a similar way, although the screens are cylindrical. Nevertheless, the squeegies for each color still force ink through the screen mesh (but not through the blocked out images).
Screen printing is expensive to set up for ceramic printing, but the unit cost drops as you print thousands of duplicate ceramic tiles.
Based on my reading, it seems that the tiles are initially formed but not glazed and not fired. At this point they are only the flat squares with any surface texture pressed into them. Then screen printing adds the decoration (patterns) using pigments (usually a mineral of some sort) that will add color but also will tolerate the high heat (up to 1600 degrees Celsius) of the firing kiln. Prior to firing, the screen printing is applied, and the glazes are added (again, glazing materials that will tolerate the high heat of the kiln). The firing strengthens the clay and makes the tiles durable, while the screen printing adds patterning, and the glazes create a glass coating (essentially) to protect against moisture and germs. Such is the screen printing, glazing, and firing process. It had been the method of choice, but it is being quickly replaced by digital printing.
Digitally Printing Ceramic Tiles
Screen printing the “biscuits” (unfired but preformed ceramic tiles with any textured patterning already pressed into them) risks breakage. After all, screen printing involves touching the unfired clay and using at least some pressure to force ink through the screen mesh. In contrast, digital inkjet printing does not touch the tile biscuits. Rather it sprays ink onto them (from a short distance) and so minimizes breakage.
In addition, screen printing creates only a limited universe of different tile patterns. To do otherwise would require many more screens with different tile patterns. In contrast, digital inkjet printing can yield an almost unlimited universe of different patterns on the tiles, so your bathroom could have few or no repeated patterns.
Also, there's a drive in ceramic tile printing (as in most other fields) to print smaller, personalized runs. With screen printing, you have to produce thousands of tiles to make the process cost effective, but with digital inkjet printing you can produce one tile, 100 tiles, etc. You don't need to worry about storage and inventory, since inkjet set-up costs are minimal when compared to an analog process like screen printing.
Therefore, inkjet printing is beginning to take the ceramic tile industry by storm. From my reading it seems that the main challenges in the application of this digital printing technology have to do with getting particles of pigment of a sufficiently large size to be usable (lightfast, and that will tolerate the heat of the kiln) but small enough to sit in a chemical suspension and travel through the inkjet printheads onto the clay biscuit substrate. Clogging printheads and pigment particles settling to the bottom of the liquid inkjet printing mixture have been serious hurdles to overcome.
The Samples I've Seen
What I find intriguing is the various samples of ceramic tiles I've seen my fiancee bring back to the condo for consideration. I just took my printer's loupe to one of them, and what looks like marble or granite or some other natural material is nothing more than a series of inkjet dots. Seen under a loupe, it's fascinating. When I look at the side of the tile, I first see a ceramic base that appears to be about 1/4” thick. Then there's a thin coating that looks like paper, although I'm sure it's a chemical ground applied as a base for the inkjet pigments (much as you would prime canvas with gesso). Then there are the inkjet dots that appear to go all the way to the edges of the tiles (which I believe is not possible with traditional screen printing on ceramic tiles). Then there is a topcoat of some kind, presumably for durability.
I know from my reading that in many cases these inkjet printed tiles are produced in such a way that the decoration is not just a surface treatment added to an already fired ceramic tile. Rather it is a part of the process that includes firing in the kiln (and therefore uses mineral-based pigments). Furthermore, it seems that approaching tile making in this way also minimizes wear and tear on the tile decoration (after all, you might have a lot of foot traffic if you're using these tiles in a commercial environment) and also minimizes fading from exposure to sunlight.
One website devoted to printing tiles even noted that theirs is not a sublimation process (presuming an inkjet carrier sheet with pigments that are transferred to the tiles with heat, by first turning the pigments into a gas that travels into the porous surface of the unglazed, unfired clay tiles). In short, this website was implying that the company's inkjet process created “real tiles” that had all the durability and lightfastness of traditionally screen-printed tiles. And the company can print just one tile or multiple tiles.
Some Intriguing Samples That Go Way Beyond the Traditional
More than the curious marriage of ceramics and printing, plus the potentially limitless future of industrial inkjet printing, I found the products themselves intriguing.
At the myriad of tile stores my fiancee and I have frequented of late for the house rebuild, I have seen everything from natural stone (quartz, marble, travertine) to inkjet printed versions of the same. In fact, I have learned to first look at the side of the tiles. Natural items have patterns that go all the way through. Inkjetted tiles seem to have only a surface deposit of ink on an otherwise blank tile. However, the products when seen side by side can be almost indistinguishable from one another. And product durability is not an issue.
Beyond the traditional look, there are also rather odd simulations, including inkjet simulations of wood on tiles as well as stone and ceramic. There are even simulations of industrial carpet on ceramic tiles, including the texture of the rug. You really don't know what you're seeing, even when you're touching it.
The key is that you can use inkjet and other digital technologies to produce almost anything that looks like something else. And they're working out the kinks. The products look good, and they're durable.
In my eyes that means that print isn't dead. It's spreading like wildfire in industrial venues.
[Steven Waxman is a printing consultant. He teaches corporations how to save money buying printing, brokers printing services, and teaches prepress techniques. Steven has been in the printing industry for thirty-three years working as a writer, editor, print buyer, photographer, graphic designer, art director, and production manager.]