Last update: 08.08.2019
Building with glass

Ceramic printing on glass

Enamels have been carefully developed for printing and firing on normal soda-lime based float glass.

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During the tempering process of the glass, these enamels melt and fuse permanently to the glass surface to form a coloured ceramic layer.
A typical enamel consists of a mix of fine ground glass flux and colour pigments together with oil- or water-based solvents and thinner. Depending on the application method the composition can differ significantly. A ceramic paint (enamel) can be applied using various techniques: screen printing, roller coating, digital printing, spraying, curtain coating or by brush.

After a special drying process, the enamel melts during firing at 500 … 650 °C and fuses to the substrate. The result is a UV-durable, mechanically- and chemically-stable, ceramic coating.

Ceramic printing methods

Roller coating

Enameling using the roll technique allows a precisely adjustable and uniform paint application. Due to the increased enamel thickness it ensures a high visual density and homogeneous appearance. This technology is adopted for covering large areas (such as spandrels) or edge enameling and is ideal for large quantities.

Roller coating



One colour screen print printed directly onto glass has a long tradition. The enamel is pressed using a scraper through the open parts of the mesh onto the glass. First, the mesh is technically prepared in open sections to be printed and closed sections (not to be printed). The open sections form the motif to be printed in this respect with the aid of the colour. Printing using the silk-screen technique allows the application of special design patterns on a glass surface but also the possibility of covering larger areas too. The enamel thickness is precisely adjustable depending on the screen parameters and enamel consumption is less compared to other techniques. This technology is ideal for high volumes and is suitable for design and edge printing. A disadvantage is the comparably high manufacturing cost of the screens.



Digital printing

Digital printing is a relatively new technology for applying images or design pattern to the glass surface. The technology includes a digital glass printer, digital ceramic ink and, typically, image processing software too.

The printer is equipped with print heads with nozzles and ink fixation (immediate drying of the droplets) allowing a single pass process even for multi-colour designs. A piezo-electric pulser releases single ink droplets very precisely. The digital printing ink is adapted to the printer hardware using very fine nozzles.

Advantages are its high design flexibility and there are no silk-screen costs.

Digital printing


Spandrel Glass

Spandrel glass is the glass that conceals structural building components such as columns, floors, air conditioning systems, electrical wiring, plumbing, etc. Spandrel glass is typically located between vision glasses on each floor of a building.

Curtain wall and structurally glazed designs often require the use of spandrel glass to achieve a designer’s vision of the finished project. Spandrel glass applications can be complementary or contrasting in colour when compared to the vision glass appearance. Typically, spandrel glass must be heat treated to avoid thermal stress breakage due to high energy absorption. Guardian has experience in spandrel glass applications and can help architects and building owners achieve the desired appearance whilst minimising the risk of thermal stress breakage.

When vision glass is specified with a high light transmission or low external reflection, an exact colour match between spandrel and vision glass is challenging. Daylight conditions can have a dramatic effect on the perception of vision to spandrel appearance. For example, a clear, bright sunny day provides a higher reflective appearance, which will improve the vision-to-spandrel match. A grey, overcast day may allow more visual transmission from the exterior and produce a greater contrast between the vision and spandrel glass. Guardian recommends that a full-size outdoor mock-up be prepared and approved in order to confirm the most desirable spandrel option for a specific project.

Spandrel glass can consist of an opacified uncoated glass (picture left), a reflectively coated glass (picture middle) or can be an insulating glass unit comprising of a solar control glass as the exterior pane and an opacified uncoated interior pane (picture right).

SunGuard® HD reflective coated glass allows for the application as monolithic spandrel. This provides an economical solution that is suitable for many applications. If the desired match cannot be achieved with the monolithic spandrel solution, an insulation glazing spandrel can be considered.

Spandrel Glass


Edge enameling – Guardian System TEA

Many situations in modern construction designs require partial or perimetrical ceramic edge print. Such as:

  • Structural glazing.
  • All-glass corners.
  • Roof glazing with glass overlap.
  • Glass louvre windows.
  • Glass fins.
  • Top and side hung windows in fully-glazed façades.

Typically, edge enameling in combination with architectural coated glass is performed by cut-to size technology with the disadvantage of additional handling steps, possible quality issues and long lead times. 
With ceramic paint, compatible coatings can be printed but often show an undesirable colour shift. 

A new technology – developed with the company Ferro – for ceramic printing of architectural coatings is „Guardian System TEA“ (TEA = True Edge Application).
This special enamel is applied directly on the coating. During the heat treatment (firing) process, the coating is completely dissolved. The System TEA enamel fuses with the glass and creates a strong bond (comparable to standard enamel on float glass). After cooling, the coating material is fully embedded in the enamel (similar to colour pigments). This patented system provides edge-deletion and enameling in one step.

Edge enameling – Guardian System TEA


Sunguard La Casa del desierto

Photo: Gonzalo Botet


System TEA enamel can be applied by roller coating or screen-printing. Most of Guardian’s heat treatable SunGuard and ClimaGuard coatings, as well as Clarity anti-reflective glass, are compatible and proven by notified body testing institutes. 

The System TEA enamel surface is also suitable and certified for structual sealant applications. Please ask Guardian’s Technical Advisory Centre for more information regarding tested combinations.

Decorative print 

Not only are the design of parapet panes (spandrels) further refined in functional terms in modern architecture but transparent elements are also receiving more and more visual and functional decorative facets. Glass offers a variety unlike any other construction material. The design can be a decorative ornament, symbol or even an all over illustration or matting. The areas that can be designed with decoration glass are multifaceted. In modern apartments, offices, restaurants and hotels, for example, design glasses as partitions and coverings maintain a balance between separating and joining with individual emphasis. Glasses with such design components achieve a high aesthetic appeal and additional solar protection. In addition, they guarantee at the same time consistency and colour fastness. In combination with solar control glass, they offer extensive, individual impulses for modern façades design.
Typically, techniques used are silk-screen printing and digital printing.

Decorative print

In combination with architectural coatings, different scenarios and consequences must be considered:

  1. Print between glass surface and coating (#2)
    • for non-heat treatable coatings.
    • requires cut-to-size technology.
    • no colour shift.
    • influence on thermal and solar energy performance of the coating.
    • additional production steps.
    • quality risks.
    • logistical and lead-time issues.
  2. Print on top of the coating (#2)
    • use of heat treatable coatings only.
    • coatings must be compatible with enamel.
    • high flexibility.
    • colour shift in outside appearance.
    • loss of thermal performance (low emissivity) at enameled areas.
  3. Print (#1) and coating (#2) are on opposite surfaces of the glass 
    • Special enamel suitable for #1 (outdoors) applications.
    • Use of mechanically stable, highly durable coatings (such as SunGuard HD) only.
    • Feasibility tests regarding processing recommended.
    • high flexibility.
    • no colour shift.