Guest post: In depth analysis of ceramic digital printing on glass

This month’s guest post is by Bernd Hoffmann of Hoffmann GTD Glas-Technik-Design, and discusses in-depth the process and intricacies of ceramic, digital glassjet printing.

If you are looking for more details, kindly visit ceramic printed glass.

If you haven’t already, you can also read last month’s introduction to digital printing on glass.

Ceramic Digital Printing-customizing Glass Façade Design

Modern digital printing technologies using ceramic inks are providing new interesting opportunities for long-lasting decorations and optical effects on glass.

This way even multicoloured very large format images and decors can be printed and fired on glass providing reflective high-resolution prints, turning the functional glass skin of a building into a more or less translucent artistic screen. After a short introduction into the basic principles of the Ceramic Digital Printing technology and the world of Glass Façade Design the presentation will give an overview about the advantages and limitations of the Ceramic Digital Printing for architectural applications. Different design intentions, challenges and achievements will be presented and discussed. TOPAZ – a helpful concept of preceding considerations for the design process of glass facades will be introduced.

Ceramic Digital Printing

Ceramic Printing

The demand for a long-lasting quality for printings on architectural glass is strongly restricting the use of organic materials in combination with inorganic, mineraloid glass. In the last century Silkscreen Printing has become the major technique for the graphical application of ceramic inks on glass. There have been many developments in the Silkscreen Printing technology trying to enhance the quality and to reduce the efforts. Even here the (organic) Digital Printing has entered the process, helping to avoid films and the photographic stencil development on screens using CtS (computer-to-screen). The Silkscreen Printing is an analog process still, even though many professionals may often wrongly talk about a “Digital Silkscreen Fritting” when they are actually looking for a “Ceramic Digital Printing”.

Digital Printing

Since the introduction of the applicable computer to the world in the 60´s of the last century, most social and industrial processes have undergone revolutionary changes. The quality, quantity and resolution of data processing has at least doubled in every decade. So nowadays the digital processing has passed the challenges of it´s analogancestors in almost every working field. Even the limits of photographic image reproduction have yielded to the quality of modern digital printing.

Decades of Resolution Decade Resolution Colour ’60s 10 black, white, grey ’70s 90 black, white, grey ’80s 180 black, white, grey ’90s 360 colour 2000 720 colour 2010 1440 colour 2880 colour

XXL-Printing

According to the use of modern graphic programs, data processing and storage the world of large format design has opened not only for highly sophisticated professionals. Every image can now be processed and reproduced in high qualities in gigantic formats.

Table 2 is showing the amount of graphical data that can be processed by modern data storage devices, to give a feeling for the amount of graphical information needed.

Data sizes for graphical reproductions using BMP files with a 360 DPI resolution. 1 m² = 14400 * 14400 pix = 200 Mpix Data Storage Device Black & White 25 MB Greyscale (8-bit) 200 MB RGB (8-bit) 600 MB CD 7 m² 4700 MB DVD 40 m² 25 GB Blu-Ray

Here we can see, that the amount of information for a high-resolution image print might be important for a smooth data-processing. One of the greatest challenges of a professional Facade Glass Design preparation is it, to determinate the best composition of vector and bitmap information according to the most important distances and effects.

Ceramic Digital Printing

The Ceramic Digital Printing (CDP) can be seen as a synergy of the advantages of the Ceramic Silkscreen Printing (CSSP) and the Digital Printing with organic inks (solvent, water soluble, UV-cured, etc.). For a successful development of the Ceramic Digital Printing on glass two main issues had to be mastered: A new system of colour-pigments with particle diameters less than some 1/100th of the
conventional sizes, performing with reliable results in the temperature range of flat glass tempering (550-750°C) and sufficient mixing properties had to be found and established.

And even more challenging, the erosive character of ceramic pigments that are usually grinding on the delicate architecture of multi-nozzle print heads, eating them up step by step within an unpredictable period of time, had to be tamed.

Advantages of organic versus ceramic materials. Organic Ceramic Water Resistant Solvent Resistant UV Resistant Chemical Resistant Chemical Resistant Scratch Resistant Colour Spectrum High Resolution Advantages of direct ceramic digital printing on glass. Analog Digital No films needed No screens needed No colour change Individual colouring Variable thickness within one layer Multi-colour registration Fine positioning & reproduction High Resolution Very thick layers

GlassJet

This issues of particle size and erosion have been solved, leading to the production of a Ceramic Digital Printing system named “GlassJet” which has been introduced to public during the Glasstec 2004 in Düsseldorf. This standard industrial printing solution is capable of printing 6 colours of ceramic pigments on flat glass directly, allowing a resolution of more than 360 dpi, using a drop-on-demand technology on areas of 2800 x 3700 mm and even 3300 x 6000 mm in a single pass.

Colourful Hi-Resolution

A high quality colourful photorealistic reproduction can be achieved. Due to the low viscosity of the inks on glass a resolution of 360 dpi in most cases will be the best setting for most spectacular results. Every single point of an artwork can be coloured and controlled individually, granting the highest quality in positioning and registration (very important for multi-coloured prints). Within one print the density of each part can be defined from highly translucent to solid, controlling the amount of ink preferred.

Optical properties of GlassJet inks

The GlassJet inks are mostly reflective to guarantee a bright colour reflection. Only the blue ink is of transparent nature to allow a nice reproduction of water and air qualities. It can be made reflective by adding other more reflective inks (white).

Certifications

Performance reliability and qualities are comparable to the common industrial standards of the professional Digital Printing. Their applicability monolithic or inside of laminated glass and/or in combination with solar-control coatings is proven.

Results

The range of chances for creating new artwork or reproducing design solutions on architectural glass is tremendous. Here you can find a selection of some designs that have been developed:

Material Imitations

Optical imitations of fabrics, streak metal, metal surfaces, carbon fibre, stone, marble, plants, clouds, streaks, drops, glass bricks and other natural or technical objects and effects have been produced with Ceramic Digital Printing on glass successfully and built into facades and rooftops:

Conclusions

The Ceramic Digital Printing on glass can substitute most of the known techniques of glass decoration up to a very high extend. Most of the effects that can be attained can be combined with one another simultaneously in just one step of production. Technical and decorative effects for new individual indoor and outdoor design solutions can be generated that have been impossible before. For architectural applications biggest advantage of the CDP will probably be the multicoloured XXL-format production, where one image can be tiled and distributed to various tiles so that every panel can own its own design without pushing the costs and efforts of production sky-high. A further advantage of the CDP is the opportunity of shortening the time necessary for a glass design development process by providing different variations of CDP-samples within very short periods of time. The production time (the print, drying and firing) of one small sample can be reduced to be less than one hour if everything has been prepared nicely.

Glass Design Engineering

The Ceramic Digital Printing is not just a technique of reproduction but can be used as a totally new technique providing effects and artwork solutions which have formerly been impossible. With CDP the faculty of Glass Facade Design is no longer restricted to standard sheet materials and standard design patterns like monochrome silkscreen rasters, for example. Sophisticated colourful graphical compositions can now be calibrated exactly according to architectural intents.

This advanced processes of creating most suitable skins for a building are no longer just about picking an artwork and ordering some print-versions on glass, but they are bearing the chance and challenge to optimize the design individually. This optimizations are depending on combinations of design parameters that often have not been relevant to be taken into consideration before. Sometimes those parameters even seem to possess uncertain definitions. Therefore we are presenting a checklist for glass design projects that will help to consider those parameters to round-up a project definition and may provide useful conventions for a plain design language:

T O P A Z a checklist for facade glass design projects

Tiling

The first step will be the determination of the maximum panel format to provide the chance for a smooth workflow without exceptions.

Opacity

The light flow is the major difference between “Glass Design” and “Paper Design”. Paper Design is based on light-reflection mainly, whereas Glass Design is handling 3 different important main characteristics of light flow:

Reflection (REF) – Transmission (TRM) – Absorption (ABS)

Reflection

Shadow box applications will be printed opaque or even solid to avoid the background to shine through. Those are working almost completely on reflection. Most of the inks of the GlassJet are of reflective nature to be compatible for outer facade design, avoiding the “church-window-effect”, the fact, that transparent colours are great for projecting transmitting light but tend to “fall into grey” being seen in reflection.

Transmission

Most facade applications will use the wide range of light-transmission.
Functional and aesthetical aspects will determine the transmission wanted. These effects can be determined qualitatively by defining the scattering of the light and quantitatively by calculating the light flow within the visual spectrum.

Absorption

The absorption will be important for the energy flow during the production process and for the energetic ecology of the mounted panel (IGU) and its environment.

Positioning

A design printed on transparent substrates can often be seen from both sides. Even if inks are printed simultaneously there will always be more or less significant differences in the performance of surfaces printed with different sequences. Therefore it might be important to determine, which sides will be most important. For translucent or transparent panels it will be essential to consider the positioning of the light and of the viewer to get an idea about the resulting design effects.

Active White

Opaque prints on glass are using the color White to print light-reflections. On paper prints those will be left unprinted. On glass, White can be functioning as a substitute for the usual paper background. Translucent prints might need the colour White to show light in reflection, but they usually will not be specified in the artworks automatically. In most cases it will be necessary to discuss the use of the White on glass in advance.

Zoom

For large architectural artworks it often is very important to choose an interesting graphic strategy for the transfer of the relatively small basic image bitmaps into large facade cladding prints, especially if people will have to live with it closely.

A more practical version of the TOPAZ checklist can be found on CERDIP.COM.

The company is the world’s best laminated glass with sgp supplier. We are your one-stop shop for all needs. Our staff are highly-specialized and will help you find the product you need.

Summary

The technology of the Ceramic Digital Printing is providing an instrumentation that has proven itself to be a real advantage in the field of designing and producing architectural flat glass, inspiring professionals to create new visions and solutions for future projects. The Ceramic Digital Printing is not just a machine of standard image reproduction, but an instrument of versatile approaches and effects, that might help to create really progressive individual design solutions, helping to add more character to the functional glass skins of modern architecture.

Facade Glass Design Service

Many developments have been made according to the new advantages and challenges of the CDP and the design and production process surrounding it. New designs and technologies are demanding proper tools, experience and sometimes even new hardware and software solutions to be developed and applied successfully. A combined Facade Design Consulting, Facade Design Glass Production, Pre-press and Production Service will be helpful to optimize a creative and productive workflow.

Design Software Solutions

Design software solutions like Bitmap-Analyzers, Bitmap-Modulators and Bitmap-Synthesizers are helping to optimize the composition of colours. (B2B-software) Even more interesting for the XXL-format imaging will be Bitmap-to-Vector modulators and synthesizers that are able to modulate or generate graphical structures by the use of vector objects according to mathematical algorithms (B2V-software). This tools will help to provide a wider spectrum of alternatives for the production of new designs.

References

All texts, pictures and tables by Hoffmann GTD unless stated differently.

1. Hoffmann GTD.
2. Cerdip.com.
3. Dip-Tech.com.
4. Interpane.com (Ipadecor K).

Acknowledgements:

1. Hoffmann GTD, Germany.
2. DipTech, Israel.
3. Interpane-Sicherheitsglas, Germany.

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Related

In part two of our coverage of printing onto glass and ceramic, FESPA UK’s Peter Kiddell explores the techniques and latest technologies used to decorate them.

When screen-printing companies decide to expand their product offerings, an area that many explore is the market for decorated glass and ceramic products.

However, lack of familiarity with the methods and materials used in glass and ceramic printing usually steers all but the most adventurous printers away from such work. 

Whether you are decorating glass or ceramic the printing techniques used are very similar all aim to achieve the adhesion of pigment to the surface and have that pigment maintains its colour or performance over the required time period.

No different to any other application but the operating conditions of printed glass and ceramics can be extremely challenging.

Total Transfer Process

When printing directly onto glass and ceramics, screen printing and pad printing can be used. There is a combination of both processes called “Total Transfer.”

This is where the image is screen printed onto a flat plate and then picked off by a silicone pad and transferred to the article. The decorated product is then fired in the normal way. 

The reason for using this process is to enable relatively thick deposits of ink to be printed with the pad-printing process, as shown in the picture below.

Image courtesy of PDS International Limited

Pad Printing with Thermoplastic Inks

Pad printing with heated plates and thermoplastic inks works very well but there are pros and cons for both systems. Four colour process is possible with inorganic Cyan, Magenta, Process Yellow and Process Black.

This is not for the inexperienced as colours can easily change in the printing and firing process. You don’t have the benefit of colour bars, greyscales or density measurement as the printed colours change during the firing process and you can’t guillotine off the colour bars.

The simpler alternative to direct printing with ceramic colour is to produce waterslide or heat applied transfers. These transfers are produced by screen printing and lithographic printing. Waterslide use water soluble glue that allows the image to lift off special paper before being positioned on the substrate.

Heat applied transfers come off the carrier paper or film when applied with a heated blanket to the substrate. In both cases the applied image has to be fired at elevated temperatures. 

Sublimation

None of these methods should be confused with sublimation transfers that appear to print onto ceramics and glass but are in fact producing an image in a polyester lacquer that has been sprayed or dip coated on to the surface.

Although very attractive this is not as resistant as fired enamels or even UV cured inks. Sublimation inks are not particularly colour safe in sunlight or elevated temperatures but it is still a big market particularly in personalisation and business gifts.

Developments in the dyes and application methods are increasing the use of the process which is ideally suited for the use of digital printing in the creation of the transfers.

In summary the options are:

• Inorganic ink that can be screen printed or pad printed but requires a kiln or lehr to fuse the enamel to the surface.
• Organic ink that can be screen printed or pad printed that requires heat or Ultra Violet energy to cure. If the curing methods is heat then the maximum temperature will be in the region of 180oC for a period of time.
• Waterslide or heat applied transfers printed with inorganic ink that have to be fired in a kiln or lehr.
• Sublimation systems are an ideal means of decorating a huge range of polyester objects and substrates.

Production of Transfers

If you don’t have the kiln or lehr, as a screen printer, the production of transfers can still  be a very good business. There are still some very able printing companies making an excellent living from this market.

Four colour process printing provides great results particularly as the firing process in the kiln helps blend the colours and reduces the characteristic dot patterns.

Transfers can be produced using multiple colours, 20+ is not unheard of. The challenge of producing waterslide transfers is maintaining the condition of the adhesive coated transfer paper. Variation in the paper during printing can wreck accurate registration.

Special dryers known as wicket dry are often used and the print shop has to have the humidity carefully controlled. Although you don’t need a production lehr or kiln to produce transfers you will need a means of test firing the applied transfers. 

With heat applied transfers the production methods are similar, but rather than printing onto adhesive coated paper a release paper is used and the image has a heat activated adhesive that forms a temporary bond with the glass or ceramic, allowing automatic application with heated silicone rubber formes. Once applied the transfers are fired onto the glass.

In this series of two parts, FESPA UK's Peter Kiddell has just touched on the topics of glass and ceramics printing. It is not easy but it can be a lucrative market.

There is a resurgence in the UK and European market as end customers want the exclusivity and cache of finely decorated glass and ceramics.

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