How Printing Works

Modern offset lithography is used to mass produce posters, books, newspapers, packing, letterheads; just about any smooth mass produced item with print on.

The term 'offset' is used because the ink is not directly pressed onto the paper. Instead, it is distributed from a metal plate to a rubber mat where is it then set on to the paper.

Offset printing can be done on either a web printing press or a sheet fed press. Web printing presses use huge rolls of continuously fed paper where as a sheet fed press, as you would expect, uses sheets of paper. Both types of printing presses produce printed material that can be cut to size after printing.
Print is now getting more advanced and computers are now an important part of the process. Computers are now used to aid design and also generate instructions for mixing ink and the distributing it to the paper.

Offset printing works because water and the inks do not mix. The images to be printed are created on the computer, and then burned on to metal plates. This uses a developing process using chemicals which is similar to photography.
The metal plates are then dampened with water which adheres to the areas without images. Next, the ink is added, one colour at a time. The ink then sticks to the areas with images.

The most modern systems use a direct to plate system in which the images are burned directly to the metal plates.

Cyan, Magenta, Yellow and Black are the most common colours used in offset printing. These colours are often abbreviated to CMYK; Black is abbreviated to K to avoid confusion with Blue. Different percentages of these colours create virtually every colour in offset printing.
Print buyers can see these colours using colour matching systems such as PANTONE. The code for that colour can be entered in to the offset printer's computer; this will calculate the percentages each colour would use.

The final printed materials produced through offset litho also dry quickly, keeping the production press moving smoothly from the printing to the cutting and binding.