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Printing: from Unclean to Clean 24/09/2012
Printing has accompanied us for thousands of years. Without printing, human knowledge and civilization may still be recorded on bamboos slips or rocks and are available only to a handful of rich people. Printing makes the dissemination and inheritance of human knowledge much easier. However, printing has not only brought us knowledge, but also pollution. Just consider the following facts:
A printing house is always a noise maker. The droning and rolling day and night often drives the nearby residents crazy, if there are any. Every year, large area of forests will be consumed for printing, which leads to billions of tons of carbon dioxide and pollutants discharged into the air and huge amount of poisonous water permeated underground.
Therefore, printing is not as clean as the shining books or pictures it has produced. Pollutants always go with it. Volatile organic compounds, or simply VOCs, are notorious and harmful by-products of printing. They are often numerous and varied. Once bonded with dust particles and other substances, gaseous VOCs will generate grey fog, which is detrimental the environment. Chemicals used in color proofing, printing plate washing, cleaning agent, printing ink, oil polish, etc, contain VOCs. Take screen printing for example. A kind of porous printing, screen printing equipment renders ink to pass through the pores of a woven mesh and be printed on papers, porcelains, etc. Normally, this printing method uses solvent-based ink which is dried thorough volatilization and VOCs are thus released into the air.

Moreover, electroplating effluents of heavy metals, corrosive liquids used for plate-making and organic matters contained in other effluents are also major contaminants in river and soil. Printing machines, air compressors, drying equipments and forming machines and even cooling towers are the sources of noise pollution. With all these factors, workers, nearby residents and people far away from printing houses, and even the animals, water plants are all victims of printing pollution, directly or indirectly.
Since printing is both indispensible to human beings and undesirable to the environment, something should be done to avoid its disadvantage and foster its strengths. Then, as good as people might expect, a new concept &ndash; green printing is put forward and soon gains its popularity.
Green printing is an environment-friendly printing which lays emphasis on environmental protection, energy preservation. The top priority of it is to develop environment-friendly printing ink, or simply, green printing ink. Made from natural materials, such printing inks include water-based ink, UV ink, etc. Unlike traditional solvent-based printing ink, water-based ink uses water and alcohol as its solvent instead of VOCs, thus it inflicts no poisonous chemical threat. UV ink can be solidified from liquid state under UV-irradiation and needs no solvents.
The best-received and promising green printing is probably flexography, a new kind of letterpress that utilizes flexible printing plate, which allows printing ink to be transferred onto materials of almost all kinds. Not only that, flexography uses mainly water-based printing ink and thus it keeps up with the greening trend of printing industry. Another new printing method &ndash; acrylic printing is a faithful user of UV ink, and discharges no volatile substances and no unpalatable odors. Furthermore, most Acrylic Printing acrylic printers  are noiseless, and pose no harm to our ears. With the development of technology, printing ink can gradually shake off the harmful solvents.
Apart from the endeavor to develop new printing inks and printing methods, there should still be efforts paid to deal with the wastes of printing. For example, the usable materials like papers can be reused; materials like plastic films which are hard to be degraded should be collected and buried or reused; harmful or poisonous gases generated by printing can be absorbed, burnt or retrieved with special equipments. By doing this, the unavoidable pollution of printing to environment and human beings can be reduced to the minimum.
With our environmental awareness awakened and aroused, green printing will definitely become a priority for the whole printing industry. But green printing is a systematical project which involves printing machines, equipments, raw and auxiliary materials, advanced technologies, even the polices of the governments and customers' acceptance, etc. The disconnection of each aspect may bring negative influences to the whole green printing industry. Thus, it still takes a long and tortuous route for green printing to turn from a tender seedling to a stout tree. We do hope one day green printing makes printing completely clean.