|Ceramic frit ink (inorganic pigments), UV-cured, or sol-gel inks for digital printing on glass?|
Which inks for digital printing directly on glass is the big question still in 2014 and as we move into 2015. Since many of our readers are print shop owners, manages, and printer operators around the world, they come to ask FLAAR for assistance in deciding which wide-format inkjet printer should they buy so they can skip screen printing and print directly on glass.
Since the Hellmuth family background is with architecture, we too are interested in printing on architectural glass. FLAAR also is knowledgeable in printing on ceramic tiles.
Flatbed inkjet printers for architectural glass decoration and decor
The world of wide-format digital printing is a world of fast printing of usually customized images, usually for short runs. A trade show booth may need glass walls, or glass table top. Or a restaurant may wish to have their logo on their windows (directly on the glass, not on roll-fed material adhered to the glass with an adhesive layer). UV-cured wide-format inkjet printers have traditionally been used for small print jobs such as these.
Or an architect may wish an entire building to have a custom appearance on the glass façade.
In the past, if you wanted long-runs of hundreds of examples or thousands of square meters, then you utilize screen printing, offset printing (for signage), pad printing, or flexo printing (for packaging, for example). But today in-line production printing is also realistic with inkjet chemistry.
But from 2012, there are many competing inkjet ink chemistries. Each has several advantages but each ink chemistry has one or two things it can't handle well. So it is essential to compare and contrast the different ink and wide-format digital printer options.
In-line printing on glass (compared with printing just one shower door)
If you need in-line printing on glass, this is a separate world of industrial printing. Durst would be an example for in-line printing on other materials (for printing on ceramic tiles, in-line or their printer for wooden décor). I have been to the Durst factory and demo rooms five times in Brixen and four times in Linz, Austria. But the first generation Durst glass printers tried to use a sol-gel kind of ink
Polytype (formerly WP Digital and originally Leggett and Platt Digital Technologies) has also moved into developing workflow for digital printing on glass, but it has not yet been possible to visit their new Polytype facilities after they added their focus on glass (I have visited their former facilities twice: Spuhl and WP Digital, but that was before they really focused on printers for architectural glass). Then a series of management decisions and bringing in many capable people but with no experience in the reality of wide-format inkjet (and laying off all those who had experience) resulted in the entire wide-format inkjet division not being able to compete with the more successful brands, and Polytype stopped making their rather nice printers.The weight of glass is considerably higher than of the normal materials commonly printed in UV printing: 2.5kg/mm/m2. I remember visiting a printshop near Milan, Italy whose manager said how much trouble his circa 2006-vintage NUR Tempo had handling the weight of large glass plates.
So taking into consideration all these aspects: in-line may require the automatic feeding system of glass in the printing machine that is going to increase the production speed tremendously due to the printing process that is continuous and simultaneous with the plates be manually loaded on the feeder in a continuous rhythm.
At Glasstec 2010 I was shown the designs and plans for a new system of in-line wide-format inkjet printing on glass. I doubt any of the competitors exhibiting at Glasstec were aware of this new system.
Plus five days after Glasstec I learned of an entirely new company that just entered the market. I doubt if any of the wide-format exhibitors at Glasstec were aware of this new competition (neither of these printers is made in China; the printer systems described here are highly sophisticated).
In other words, what you saw at Glasstec 2010 was only the tip of the iceberg.
Misleading information in UV printer spec sheets
For printing on glass, I would estimate that 90% of the UV printer manufacturers claim their machines can print on glass. Just look at their spec sheets and advertising claims.
FLAAR does not accept these claims on all their spec sheets. In most cases these claims are misleading at best and usually unrealistic. The only companies where I have seen experience with printing on glass would be
But beware of buying used printers of brands which have disappeared, because spare parts for IP&I are close to non-available. And spare parts for most Chinese printers are rarely easy to find even after one or two years.
During 2010, other UV printer manufacturers are showing glass versions of their flatbed or combo transport belt printers. I saw these other brands at Glasstec 2010 in Duesseldorf Germany, from which several FLAAR Reports on digital inkjet printing on glass resulted. Then I attended Glasstec 2012 and have just been at Glasstec 2014 two days.
Glass printing with most inkjet printers requires pre or post-treatment
I am only convinced that a manufacturer can legitimately sell into the glass market when either I see a chemist in their company headquarters who knows glass and or ink chemistry for glass, or when I see a relationship with a major university chemical department or other comparable technology department (WP Digital with the University of Bern).
For IP&I my documentation was visiting a printshop that printed on glass year in year out. Unfortunately the team at IP&I did excellent engineering but had other corporate issues and the company folded. But the printers themselves were very nice (but not realistic to get spare parts for companies which no longer exist).
Merely putting glass samples in your booth is not enough. Merely listing glass in your spec sheet is worse.
And I am not impressed by any company that says they don't need a primer. In order to believe that I would need to see significant glass decoration companies daring to sell such a product to a skeptical end-user. If you are using UV-curing inks, glass requires a pre-treatment and in many cases needs post-treatment as well.
If your UV ink needs no primer, then you probably need post-treatment, namely firing in a special oven at high temperatures for about 20 minutes. It is not appropriate to sell a printer without the entire workflow machinery. Again, we congratulate WP Digital and GCC for their experience with the complete workflow for printing on slippery surfaces. And I am impressed by the progress made by SkyAir Ship in handling the physical sheets of glass on their printer (glass is heavy, and obviously fragile).
I can add additional UV printing companies to the list of reliable resources with realistic factual knowledge of glass decoration when I see their ability in their factory and/or in their headquarters demo room.
Or, you can laminate the glass
Another way to protect the glass is to sandwich it between another layer. This way no one can use alcohol, Windex or other cleaning fluids, and no one can scratch it. Just hope that no condensation gets inside from change of temperature over the seasons.
But if you laminate your glass then indeed you may not need to heat-treat it after printing or in some cases even prime it before printing.
But… what about stacking the glass after it is printed, and between the time it is printed and when it finally gets laminated! How many of the images will be scratched or otherwise marred?
Or you can print on other (film) material and sandwich that between glass
If you do not want to print directly on the glass (for many reasons), you can print on films and sandwich that between layers of glass. If you use the correct materials the result is triplex safety glass.
Be aware that most special ink for printing on glass is dull and unattractive
At APPPEXPO in Shanghai about three or four of the booths were using a UV-curing ink for glass from Toyo (even when they were not actually printing on glass). Unfortunately the color and saturation of this ink is not very attractive (a polite way of saying it is dull and boring).
I have seen other glass ink from other brands that is even worse (so dull I don't know why they bother to show such weak samples at a public venue).
So if someone promises you an ink that will adhere to glass, be sure that the colors will pop. Otherwise, a dull image on glass is less inspiring than a dull image on PVC.
In the meantime, on this FLAAR web page, I will list some glass decoration resources.
My interest in glass comes from my background in architecture. Half of my family for three generations have been architects: just Google Hellmuth architect and you will see why I studied architecture my first three years at Harvard. 100% of the entries for all initial complete page after page of Google results are all family. But for my junior year I took a year off to do architectural history research on 8 th century Mayan temple pyramid and royal palace architecture of Peten, Guatemala, and I stayed in archaeology for many decades, moving from Harvard through three research positions at Yale. Being an archaeologist meant I spent many years looking at glass: museum exhibit cases!
But most museums are too static, a polite way of saying a tad 18 th century. Surely there are ways to make a museum come to life (and I don't mean only at night in the silly way as in the movies that entertain you as you fly on an airplane and need to watch mindless movies to relieve boredom).
So printing on glass is because I enjoy all aspects of architectural decoration, I seek better methods to decorate museum glass (exhibit cases), and I am inherently interested in innovative technology per se.
Our interests in printing on ceramic tiles, metal, and glass require research, for which reason we appreciate when corporations host our visit to their facilities. Hosting a visit means covering the (economy) airfare, hotel, meals, and local transportation and a modest stipend to help cover our costs in reaching 470,000+ print shop owners, managers, printer operators and other companies and individuals around the world who wish to learn about flatbed printers.
Our FLAAR Reports have been updated with additional discussions of printing on glass in our sister site, FLAAR-reports.org.
Our Hellmuth family background in architecture is a help, as is our decade of experience with UV-cured flatbed printers. Of course today there are additional ink chemistries, which is all the more good reason for new research projects here at FLAAR Reports.
Decorating Ceramic tiles: similar issues to printing on glass
As an archaeologist I have an even more natural interest in painting on fired ceramics. Indeed one of my specialties in Mayan archaeology is the iconography of symbolism on painted funerary ceramics, 4 th -9 th centuries AD, Guatemala, Mexico, Belize, and Honduras. I specialize also in the digital photographing recording of these Classic Maya vase paintings (also see www.maya-archaeology.org).
For printing on unfired ceramics, Durst provides special printers for this industry. But most needs for decorated ceramics are not from factories, but from artists and architects and graphic designers: they need to print designs on ceramic tiles that are already fired. Here the best company is GCC: they have two separate chemical companies who have created the necessary primers.
I hope that in future updates on this page I can add additional printer manufacturers to the list of recommended resources. For GCC I know about their capability since I have visited the chemical companies in Taiwan and China (near Shanghai). There are already FLAAR Reports about these visits.
Any company that claims they can print, with UV-cured ink, on fired clay tiles, with no chemical treatment are even less convincing than a company claiming the same unlikely workflow for glass.
Anyone can print on glass and on tiles: the question is whether it will fall off after a few months, especially if subjected to heat. The tiles we printed at Gandinnovations factory were put on top of our microwave oven and the entire layer of ink puckered up and came off completely ( meaning that 100% of the ink layer came off).
I thank Diana Dogaru of WP Digital (now Polytype) for providing helpful, current, and useful information on glass conferences and glass symposiums. She has considerable real-world experience in UV-curable printing on glass (as well as color management and other aspects of grand format printing, both traditional solvent and the latest UV-cured). Unfortunately Polytype is no longer making wide-format inkjet printers, and Diana has moved on.
I thank the management of SkyAir Ship for arranging that the FLAAR Technical Writer on UV-curing printers (Jose Melgar) and myself could spend several days visiting their factory and demo room in China two years ago and again a second time during October 2010. Sky Air Ship is the #1 seller of UV-curable flatbed printers inside China. Most of their printers are used for decorating glass. Their glass industry partner in America, IGE Solutions, exhibited their flatbed printer at the major glass decoration trade show in Atlanta. Mark Ma from Sky AirShip was there.
I thank John Vu, TMP Glass Style Corp, (Thien Minh Printing, and Thien Minh Design Fine Art) Ho Chi Minh City, Vietnam, for providing hospitality while inspecting his extensive glass working and glass printing facilities in Vietnam during 2009.
Wide Format Printers