OFFSET.

Offset printing remains the most common type of printing in the letterpress industry.

Offset printing is indirect type printing: the image is created on a master plate, from there it is transferred to a rubber support and, by means of this, it is printed on the sheet of paper. In fact, the rubber allows you to print with great precision even on surfaces that are not exactly smooth, as is the case with some types of paper.

It is based on a mechanism made up of three cylinders. A very flexible aluminum plate is placed on the first cylinder: this is the matrix of the image that has been inked. The second cylinder is covered with a rubber fabric and receives the image from the matrix and then prints it on the sheet. The sheet passes between the rubber cylinder and a third cylinder called the counter-pressure cylinder, which favors the correct printing of the image by pressing the sheet on the rubber cylinder. Other small cylinders work on the matrix, called inking rollers —which transmit ink from a bucket to the matrix— and dampening rollers —which transmit a water-based solution from a bucket to the matrix. The preparation of the matrix is ​​based on the principle of chemical and physical repulsion between water and fatty substances —The precision of this simple mechanism is measured in microns and is a legacy of lithographic printing from the end of the 18th century.

But the evolution of Packaging has meant that new elements were added to this process to give different properties to the graphics: Metallics, Varnishes, Fluorescent Inks… This is achieved with an Additional Unit also called a varnish body.

Normally it is made up of one or two flexographic printing units and is very important as it gives the final high quality finish to the printing.