Offset printing

Offset printing is one of the most widely used printing methods in the industrial printing sector.

History and origin

Offset printing has its roots in the 18th century. Its development began when a Czech stage designer was looking for a cost-effective way to reproduce his sheet music.

At first, he used raised printing forms made from limestone. The areas intended for printing were covered with grease, while the areas that were not meant to print were treated with acid. After moistening the stone with water, ink only adhered to the greasy areas, while the dampened non-image areas repelled it. This principle made extensive etching unnecessary and still forms the basis of offset printing today.

In 1912, the first offset printing press was presented in Leipzig. Today, offset printing is a standard process for larger print runs and is used wherever consistent quality, precise color reproduction, and efficient production are required.

The process

Offset printing is an indirect printing process. This means that the ink is not transferred directly from the printing plate to the paper. Instead, a rubber-covered cylinder is placed between the printing plate and the printing sheet. The ink is first transferred from the plate to this rubber blanket and then from the blanket onto the paper.

Before printing can begin, several preparation steps are required. A separate printing plate is created for each printing color. In standard four-color printing, this means four printing plates: one each for Cyan, Magenta, Yellow, and Key, which refers to black. These four colors are commonly known as CMYK.

Each plate is mounted in its corresponding printing unit. An offset printing press has a separate unit for each color. The printing sheet passes through these units one after another, with the colors being printed on top of each other to create the final image.

For an optimal result, the print file must have a sufficiently high resolution. The final print quality also depends on the properties of the material being printed, such as opacity, grammage, surface structure, and printability.

The actual printing process is carried out with the help of three main cylinders:

• The prepared printing plate is mounted on the plate cylinder. The areas intended for printing accept ink, while the non-image areas are dampened with water so that they repel ink. In modern offset printing, waterless offset processes are also possible. Instead of water, which often contains additives, silicone can be used as an ink-repelling material. This method does not require special papers and can be used with standard printing sheets.
• The correctly oriented image is first transferred in reverse from the printing plate to a rubber blanket, which is mounted on the blanket cylinder.
• The reversed image is then transferred onto the paper in the correct orientation. The paper passes between the impression cylinder and the blanket cylinder, allowing the final printed image to appear the right way round.

Advantages of offset printing

Compared with letterpress printing, offset printing requires less preparation and is therefore particularly suitable for medium to high print runs. Once the printing plates and machine settings are prepared, large quantities can be produced efficiently and with a consistently high level of quality.

One of the key advantages of offset printing is its even and precise print result. Colors can be reproduced accurately, fine details remain sharp, and the quality remains stable throughout the entire print run. This makes offset printing especially suitable for professional printed products where appearance, consistency, and brand presentation are important.

Offset printing is also highly versatile. It can be used on a wide range of paper types, cardboard grades, and other printable materials. This makes it a reliable choice for premium packaging, folders, brochures, stationery, and many other printed products that require a refined and professional finish.