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 is first evidence of their existence. For example, the Chinese used the juice of the Rhus tree in order to produce coatings. The German word for coating, which is “Lack”, derives from the old Indian Sanskrit word „laksha“. Laksha means “one hundred thousand” and refers to the high amount of mealy bugs that were 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, also 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 coating facility. Into these coating facilities, printed sheets were delivered after several days of drying. After varnishing, mostly with solvent based coatings, the printed sheets were sent back to the printing house for further processing. No wonder that the production of a folded box could last up to three weeks.
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 odour 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 also transferred to the graphic arts industry. 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 waterbased varnishes. At the same time, manufacturers of printing presses started to convert their dampening units in a way that waterbased 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 waterbased 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 waterbased coatings was born.
Big steps in the development of overprint varnishes
In the following years, coating technology could be more and 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. These coatings consisting of natural resins and waxes firstly enabled the production of printed products totally based on renewable resources with regard to their consumables.
Since spring 2012, a new technology concept has the potential to be established in the market. TerraCross UV curing waterbased coatings are the ideal combination of waterbased and UV based coatings and join the strengths of both technologies.