HISTORY OF OVERPRINT VARNISHES
From the mealy bug to a coating
Coatings are part of our daily life. Even before the birth of Christ, there has been first evidence of their existence. For example, the Chinese used the juice of the Rhus tree to produce coatings. The German word for coating, which is “Lack”, derives from the old Indian Sanskrit word „laksha“. This refers to “one hundred thousand” and to the high amount of mealy bugs necessary to win shellac out of their rosiny metabolism products.
Until the beginning of the Industrial Age, coatings had been mainly used for visual finishing purposes. Later on, their excellent protection capabilities were recognized. Companies that specialized in the coating production began to develop; the association of the German coating and printing inks industry was founded 1900 in Berlin.
Varnishing in the graphic arts industry
New developments, for example in the area of binding agents, made it possible to adapt coatings to the requirements of their users. However, the printing and varnishing process at this time could take several weeks. In the 1950s and 1960s it was normal to print in a printing house, but to varnish in a separate facility. There, printed sheets were delivered after several days of drying. Having varnished, mostly with solvent-based coatings, the printed sheets were sent back to the printing house for further processing.
Apart from coatings based on solvents applied offline, also oil-based coatings were used in the inline process. These coatings could be processed via the ink duct, just like oil-based offset printing inks. However, several disadvantages existed, as for example a slight yellowing, a slow drying or disturbances in odor and taste with regard to food packaging.
At the end of the 1960s, chemistry began to move forward. One example is the development of the UV technology. Although its origin can be found in the wood processing industry, UV technology was transferred to graphic arts. Moreover, for the first time manufacturers of raw materials succeeded in developing polymers based on water for the graphic arts industry. These polymers enabled coating producers to formulate water-based varnishes. At the same time, manufacturers of printing presses started to convert their dampening units in a way that water-based coatings could be applied. However, compared to traditional solvent-based coatings, results were rather insufficient.
This situation changed at the end of the 1970s with the increased use of coating units integrated into sheet-fed offset printing presses. A development that was recognized by ACTEGA Terra – at this time known as Joachim Dyes Lackfabrik – at a very early stage of time. As a pioneer in the area of overprint varnishes, ACTEGA Terra brought the first water-based coatings for the printing industry to market. Quality of varnishing clearly increased. With time, a well-formulated coating series was developed meant for the application out of the coating unit in sheet-fed offset. The product line TerraWet Water-based Coatings was born.
Big steps in developing overprint varnishes
In the following years, coating technology could be more improved. By means of the change from two-roller-systems to chamber doctor blade systems, the application of coatings became more homogeneous. Coating result were reproducible by means of the defined coating application amount. Additionally, it was now possible to process coatings that contained pigments, as for example pearlescent or metallic coatings.
As the coating technology developed, also new coating requirements appeared. Higher machine speeds and new press configurations made innovative coating systems necessary. Whether printing machines with a coating unit after printing or before printing, double coater or coating devices before perfecting; today's coatings must fulfil many tasks. These include the protection of a printed product and the high-value finishing, but also the extension of printed products by important functions, such as barrier properties. Moreover, coatings have to provide productivity in the printing process and further processing as well as they need to offer safety by means of the fulfilment of food law requirements. In order to meet all these demands, research and development was -and still is- the condition.
Additionally, the environmental thought has come into focus within the last years. With the development of TerraGreen coatings based on renewable resources, ACTEGA Terra succeeded in introducing a real technology shift. Since spring 2012, a new technology concept has the potential to establish in the market. TerraCross UV curing water-based coatings are the ideal combination of water-based and UV coatings as they combine the strengths of both technologies.