A Quick Explanation of Full Colour Printing

Full colour or CMYK printing is when a graphic or photograph that has many different colours, shades and tones is separated into only four process colours; C or Process Cyan (a pale bluish colour), M or Process Magenta (a reddish colour), Y or Process Yellow and K - Process Black. Each of these separated colours is assigned a percentage, which when recombined will approximate the original image. A printing company will typically receive digital artwork from a designer or advertising agency that has been saved as CMYK separations.

The pre-press department then images the file onto four separate plates, each with the appointed percentage screen of either C, M, Y or K. These plates are then fastened around cylinders on the printing press and the machine is then inked up with process inks, also known as CMYK inks. The Cyan plate will transfer the Cyan screen with Cyan ink onto the paper, the Magenta plate will transfer the Magenta screen with Magenta ink onto the paper and so on, until the original image has been reproduced. In fact, the printing plates never actually touch the paper, but transfer the images onto printing *blankets*, which apply the image to the paper as it speeds through the various printing stations of the press.

Each of the CMYK screens are made up of tiny dots, which must fall in exactly the right place on the paper in the course of the printing process to re-produce the original image. This printing process is called Registration. If one of the screens is not in register with the others, changes in colour, tone and blurring of the printed image will occur. Often, at the beginning of a print run, some sheets are sacrificed (commonly called print make-readies) while the machine minder busies him or herself with ensuring proper registration. In the past, this could take some time and paper wastage together with the print make-ready time was carefully monitored. Today newer presses have electronic registering devices, which allow for quicker make-readies, spot-on, speedy registration and much less printing waste.

Full colour or CMYK printing is also know as four colour printing. Four colour printing presses are standard for full colour print runs, but modern print shops often boast five colour, six colour, eight and even ten colour printing presses. This allows other colours, specifically corporate Pantone colours, gold, silver, bronze and even special gloss and matte coatings to be applied to the paper stock during the print run. In most cases, these advanced printing presses also allow both sides of the paper stock to be printed simultaneously. With standard four colour printing presses, one side of the paper stock is printed first and then manually turned or tumbled and sent through the printing press again to print the other side. The ability to print both sides of a paper stock simultaneously is referred to as print perfecting.

For more information, contact Dean Young on Tel +27 11 708 7807 or Fax +27 11 708 7845.