Relief printing

The high pressure is the oldest printing process. The classic and ascribed to it in Europe Johannes Gutenberg method is the movable type printing. The printing areas are above. Be reprinted only the upright lines, ridges or areas of the printing plate. It is a direct printing process, that is, the printing plate is the color directly on the print substrate, such as Paper.

Pressure support are either single letters, molded header lines or clichés.

History

A kind of high pressure is the pressure stamp. The first known stamp comes from the Ancient Near East. In ancient times, it was mainly the materials clay or wax, in which the stamp forms have been pressed. The earliest prints were stamping or blind Prints without ink. A well-known medieval example of the pressure in the sound is Prüfening consecration inscription of 1119.

The art of cutting and engraving stamp was known since the 4th century. Already in the 8th century, the high pressure was applied by the Chinese. The oldest surviving printed book dates from the year 868, it is already contained in woodcut -made illustrations and a cut in the wood block letters. Johannes Gutenberg invented the printing press and the modern printing press in the 15th century. This learned the printed book a uncommon prosperity and spread around the world. By the end of the 18th century, there were no significant changes in this area. Until the 1970 into the high-pressure was the most important method for the manufacture of books. He now plays in comparison to other printing methods (eg offset printing or digital printing) subordinate role.

Method

The high pressure is a mechanical printing process. The printing areas are above on the print substrate, while the non-printing areas are recessed. Since the high pressure is a direct printing process, that is, the printing plate is the color directly on the substrate from the printed image on the printing medium has to be reversed. The print image is first immersed in paint and then pressed against the substrate. Almost all papers and boards can be well used.

We distinguish several kinds of printing forms depending on the nature. Hard letterpress printing plates are made of wood, metal, copper, zinc, iron, steel, brass or an alloy of lead, antimony and tin. They have by their high hardness and high toughness. This allows you to print high volumes.

Flexible high-pressure forms consist of linoleum and soft and hard rubber. Due to their high elasticity only one print short runs is possible. The plastic pressure carrier made ​​of plastic, celluloid, cardboard or synthetic resins. The individual letters are made of lead ( lead type ), wood or plastic. Stereotypes are made of zinc or plastic. To duplicate clichés inexpensive and fast, stereotypes of lead are produced. For blind and hot embossing clichés of brass alloys, zinc and steel are used.

As important for the printing, the surface condition of the printing plate. Whether the surface rough, porous or smooth is definitely the color image when rolling and the color output when printing. For example, the copper plate much of the captured color again. The zinc and iron plates, however, retain much color back.

A further printing medium, the winding plate which is mainly used in the letterset process. The winding board is a flexible photopolymer relief printing plate on which the printing parts are also sublime. Templates here are negative films. A dressing is necessary in this process in order to ensure an even transfer of ink to the printing material can. Today, it happens hardly by hand, but using a prepared slide. The finish is carried out chemically.

Work routine

First, the lead type is set, etched clichés, respectively, reproduced the pictures. After the break or page assembly, the imposition and the mold assembly to be made. After setting up and trimming the printing press, the colors are set up and made ​​the contact pressure.

Features

The image of the high pressure is recognizable by the distinctive dot fringes of the letters. Furthermore, it can be seen a shade on the back of the printed sheet. A slight relief is palpable. This method can produce very sharp printed images. Another feature of the high pressure is that the printing plates are very costly to manufacture as opposed to the printing plate of other printing methods.

Application

The high pressure is scarcely used today. The production of printing plates is expensive. Also costly is to set them up as a dressing must be carried out. For storage of the set a lot of space is needed. The letters are bound in the standing type and can not be used.

Today technically very demanding print graphics or artistically designed books will be made ​​in the classic high pressure almost exclusively. In the field of art belong to the high-pressure process of woodcut and wood engraving and linocut. A special type of high pressure is of type character or indirect high pressure, which is often incorrectly referred to as dry offset. For large projects, the letterpress printing has become material and time -consuming and uneconomic. Some small print possess but today lead journals and presses in order to produce, for example, obituaries quickly. The common saying in print " customer sitting on the stairs and cries " has its origin in a death case, but meant that the printed matter was immediately needed.

Printing machines

There are several printing machines for the high-pressure method:

• Platen presses operate on the principle of surface pressure against surface, the substrate is pressed with great force against the printing medium. On these small presses are possible prints up to a size of A3.

• Stop cylinder Schnellpressen allow pressure to a format of 72 × 104 cm. Here the paper is stretched on a cylinder and rolled across the flat printing support. Here, you can distinguish between one-color and two-color presses. Since only about 5000 prints can be produced per hour, this method is hardly used.

• Rotary printing machines work according to the principle to approximately round, that is, the paper passes between the plate cylinder, the printing carrier, and the counter-pressure cylinder, and decreases the paint. The face and reverse printing are possible in a single pass. In addition, several plate cylinder can be connected in series in such a way that multi-color printing in a printing operation are possible. The pressure performance of this machine is 30,000 impressions per hour. Folding and numbering are often connected to the machine, so that the production process can be further streamlined.

• The Cameron - high-pressure roller press is a special form of hypertension. On two endless rotating belts for recto - verso printing flexible photopolymer plates are attached. In the first printing cycle the entire paper web is printed in straight printing. In the second printing operation of the reverse printing is performed. Subsequently, the pressure further processing takes place.