Offset printing

publication date 24.03.2008

Offset - color registr

Offset printing is based on application of liquid color inks in successive steps. It is very suitable for high-quality printing of a very high number of copies. 

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Offset printing technology, which has been known unchanged for more than one hundred years, is based on the principle of successive application of liquid color inks. A color picture is divided into two or more so-called printing plates each of which is designed to transfer one color part of the picture onto the paper. Most frequently, four such plates are applied representing the most widespread color scale CMYK: C – Cyan (azure), M – Magenta (purple), Y – Yellow, K – Black . This application in successive steps results in a color register that produces the desired result. 

Offset printing utilizes printing plates, the production of which is not exactly cheap, and they can only be used for a single document you need to print. Having been used in printing, the plates cannot be recycled. Their cost has to be included in the price calculation. Likewise, the cost of preparatory pre-press work on the offset printer is significantly reflected in the final price. It is a very exacting affair indeed. Printing alone, then, is very cheap. On this account, every offset master printer tries to print larger series. The pre-press work on a leaflet being the same, the total price for printing 500 copies will come to approximately CZK 2.300,- (CZK 4,60 per copy). When printing 5 000 copies of the leaflet, the price is going to drop sharply down to CZK 0,68 per copy, while the total price of the entire order is only to rise to CZK 3.400,-.

Quality of printing

The best printing quality available is naturally very sensitive to the quality of the input data. Apart from the register colors, offset technology also prints the so-called spot colors; they are colors that cannot be achieved by combining the CMYK colors and include gold, silver (metallic colors in general), most Panthone colors, reflective (luminous) colors. 

Range of materials suitable for printing

Offset printing allows the widest choice of different materials, from low basis weights (50g/m2) up to very high ones (500g/m2). The offset technology can be applied on the largest scale of papers, with the two only limitations being the price criterion and the ability of suppliers to acquire the selected material. Stabilization of ink is effected after the particular ink has become dry on the material. 

Formats of printed materials

The biggest printing machines (except for wheel printers) are able to print on the B0 format, which is a paper sheet with dimensions of 1000×1414 mm. However, most often, machines of the B1 - 707×1000 mm and B2 - 500×707 mm print formats are used. The sheer bulk of materials is subsequently, after printing, cut into the desired final format – for instance A4, A5, B5 and the like. 

The positive aspects of offset printing: 

  • the number of copies from 400 up
  • profitable printing for large series of posters, leaflets ... 
  • high quality of print and a large choice of materials suitable for printing on 
  • and other.

The negative aspects of offset printing: 

  • high requirements for print data 
  • time-consuming pre-press work and production 
  • impossibility of printing variable data 
  • impossibility of printing small series 
  • and other

Vít Hudec

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