Offset printing is a special technique for transferring images from form to paper, plastic or polyethylene. When using this technology, the impression is not made directly, but through a special shaft. As a result, the image is not mirrored, but straight.
A bit of history
Once a seal using shapes and colors was called lithography. This word was invented by the German inventor Johann Alois Senefelder, who lived in 1771-1834. It is formed from the Greekgrapho (I write) andlithos (a rock). Senefelder - the first printer that used the method of printing on paper using forms made of limestone. At the time of this inventor, the ink was transferred to the paper directly from the stamp.
Modern lithography is a relatively complex process, in which several different materials are used. Initially, the image is etched on a flat surface. Usually it is aluminum, plastic or zinc sheets. Hence the name of this type of impression - flat offset printing. Then, in a special way, the pattern is transferred to a special roller, covered with elastic rubberized fabric, which is part of a complex design - the printed section. And only after that the drawing is transferred to paper, plastic or film.
The offset printing method is, therefore, a special technique for transferring an image from a solid form to paper or polyethylene. It includes such steps:
The engraved form cylinder is in contact with a water-moistened roller, which is then moistened.
Further, the mold is in contact with the rolling shaft, which is part of the inking unit. As the form is already moistened with water, the paint sticks only to the engraved areas.
At the next stage, the form roll touches the blanket of the cylinder, painting it, and from here proceeds to paper or film.
This technology allows you to get very high-quality images with many small details. After painting, the paper or film enters the drying machine, and then - to the final processing (cutting, gluing of finished products, etc.).
The technological process at all stages of the work in the printing house is monitored by a person of a special profession. Such an employee is called an "offset printing press". What kind of profession is it and what is its specificity, it's easy to guess. The specialty of the printer presupposes that a person primarily has such qualities as a good artistic taste, a developed sense of form, a long-term imaginative memory.
Applying multi-color images
Offset printing is, as you can see, a method that is rather complicated technologically. In this case, the method described above can also be called the simplest and cheapest. There are much more sophisticated technologies of offset printing. According to the technique, as one can notice, only single-color images are obtained. In order to print more complex drawings, the so-called four-color technology is used. In this case, different colors are created by mixing the main colors: cyan, magenta, yellow and black. The abbreviation CMYK is used for their designation.
Used for multi-color printing machines have four sections. Sometimes five-section equipment is used. In this case, an additional roller is installed on the machine, intended for varnishes and other coatings.
Often people who want to order, for example, advertising on packages or packaging, are interested in how offset printing is labeled. 4 + 4 - what is this designation, for example? The answer to this question is simple. This marks the products with offset printing printed on both sides. In other cases, the notation is interpreted as follows:
1 + 0 - one-sided black and white printing,
1 + 1 - double-sided black and white,
4 + 0 - one-sided color,
4 + 1 - one-sided color with drawing on the reverse side of a sheet of black and white pattern.
According to the type of source material, only two main types of offset printing are used in printing houses: sheet and roll. They differ primarily in terms of productivity and quality. In the first case, already cut sheets of paper are placed in the machine, so printing images is very slow. But the drawings themselves are obtained as high as possible.
Roll offset printing is a technology in which a very long tape of paper or film wound on a shaft is loaded into the machine. The image imaging process in this case is continuous.
Techniques of the print
There are also ways of drawing a picture, like deep and high offset printing. In the second case, the impression is obtained due to the pressure on the paper of the protruding (high) parts of the engraving. The second method is technologically somewhat more complicated. When it is used, the paint fills the deeper parts of the engraving. Drawing on paper in this case is also transferred when touched, but without pressure. The whitespace is simultaneously cleaned with a special tool - squeegee. This technique is used in printing shops most often. The fact is that by adjusting the depth of engraving, it is easy to make halftones and widely use the technology of light and shade.
Let out production
Offset printing is primarily a technology that allows you to get very effective images at minimal cost. Drawings made using this technique were seen, of course, without exception. For example, this is the way logos are printed on household plastic bags.
Also, some companies practice offset printing business cards. What is it, probably, everyone understands. On pieces of thick paper or plastic are applied. position and other information about a person. Offset printing allows you to get very beautiful business cards in any color solutions. In this case, you can use a variety of design styles.
The peculiarity of this technique is, among other things, that it allows you to apply beautiful drawings with small details even to a not very high-quality medium. After all, the main printing element in the sections is covered with a rubberized elastic fabric. Therefore, the paint falls very well even on a surface that is not too smooth and has roughness.
Offset printing paper is, however, a product with some special qualities. Usually this material is made from white, environmentally friendly pulp. The main distinguishing feature of such paper is high density. The fact is that on too loose sheets of paint begins to leak on the reverse side.
Recently, another technique of image imprint - digital - has been widely used. Offset printing is a technology that allows you to get very high quality drawings. However, the digital method is considered even more perfect. Its advantages are not only in the highest image quality, but also in the mobility and speed of printing. To make with its use, for example, the same business card can be directly in the presence of the client.
The cost price for digital printing eventually turns out slightly smaller than that of offset printing. However, this method is usually used for the production of printed products only in very small runs. This is primarily due to the peculiarities of the equipment used for printing. As you can already understand by name, images are produced in this case using printers of different designs.