Precise Colour in Large Format Printing

Printing on large format gauze is a science unto itself. Commercial printers use colour measurement equipment to assure consistent colour but the Instruments typically used in the printing industry cannot provide accuracy and repeatability with such textured and transmissive materials. KONICA MINOLTA has a solution that is able to deliver the necessary accuracy to ensure that 12‘000 m² of gauze can be printed within required tolerances.

Modern glass claddings are not simply transparent but are designed in colours. The colour effect is achieved using a textile gauze which is laminated between two panes of glass.
Sefar AG from Heiden, Appenzell in Switzerland produces the SEFAR^® Architecture VISION glass cladding range using a patented process to ensure that 99,8% of UV-energy is blocked whilst maintaining the outside view. The desired colour is produced using a digital printing process and aside from the size (which can easily reach thousands of squaremeters), the biggest challenge is the consistent reproduction of the colour.

Central-Switzerland based Makro Art AG specialize in digital large format printing and have printed gauzes for claddings up to 12‘000m² for Sefar AG. During a testing phase the specialists analyzed the printability of the VISION-gauze as well as the fidelity of the reproduction of certain colours. Reto Bussmann, Head of Production at Makro Art AG remembers: „We spent a lot of time comparing reference samples and test prints. The challenge is the composition of the gauze: Depending on the angles of viewing and light source the colour appearance changes a lot.“

In addition, the yarn count of the gauze depends on the intended usage of the project or panel. As the substrate has a significant influence on the final colour the printing machine has to be set up for each new gauze. Creating a print which looks exactly the same as a reference sample is essential due to the size of the finished product and its visibility, this requires far tighter tolerances than conventional print jobs.

Appropriate measurement equipment

A measuring device is required to accurately characterize the colour and densitometers have been widely used for this task in the printing industry for decades. Densitometers are mostly used in conventional printing to detect the thickness of the ink film.

Unfortunately the measurement accuracy on gauze was not sufficient. The gauze has a 3-dimensional structure, a high transmission factor and a metallic surface. Conventional instruments illuminate the sample from 45° which causes shadows between the fibres and stray reflections from the textured metallic surface. Both lead to measured values which are too dark.

The solution is using appropriate measurement geometry: The KONICA MINOLTA CM-2600d uses an integrating sphere to provide diffuse illumination (commonly used in industrial colour measurement). This approach overcomes both of the issues encountered by conventional print colour measurement instruments.

Constant control

KONICA MINOLTA‘s technology and expertise enables industrial scale digital large format printing within tight tolerances. Makro Art AG can correct the smallest deviations immediately and adjust production accordingly. In order to print 12‘000 m2 of gauze for cladding a closed loop process is extremely important. „We had to change our way of working completely“, explains Bussmann. In the prepress stage the colours have to be adjusted using the correct ICC-Profile. The basis for this is clearly defined reference values in CIELAB colour space which are transformed to optimal CMYK values to be used in the layout software. In order to realize this step in the workflow KONICA MINOLTA offers an automated profiling solution: Using an xy-stage thousands of colour patches can be measured quickly and accurately. Bussmann: „That is well known ICC Colormanagement but using measurement technology that enables us to accurately judge if we are on target or not.“

To ensure a constant colour quality throughout the entire project the measurement results of each print run are constantly tracked and if necessary used to generate optimisations for the next print run. Every single parameter of the RIP-Software is controlled and reported digitally. The same is true for the digital files which are sent to the print room - for every single file a digital log is available. To complete the detailed control and reporting process, every single quality control measurement is stored in a QC report using Konica Minolta‘s Catch QC solution.

Due to well defined procedures and accurate measurement equipment Makro Art AG is able to fulfil the colour fidelity required by Sefar AG and print on large format gauze to an industrial scale. Meanwhile the company is using the colour management equipment to optimize the quality for their other printed materials such as textile printing and signage. Thus clients of Makro Art AG benefit from outstanding colour quality which would not be possible using traditional equipment of the printing industry.