The offset printing is a special technique of transfer of the image from a form on paper, plastic or polyethylene. When using this technology, the impression is not carried out directly, but through a special shaft. As a result, the image is not mirrored, but straight.
A bit of history
Once printing using forms and paints was called lithography. This word was coined by the German inventor Johann Alois Senefelder, who lived in the years 1771-1834. It is formed from the Greekgrapho (writing) andlithos (a rock). Zenefelder is the first typographer who used the method of printing on paper by means of forms made of limestone. At the time of this inventor, paint was transferred onto paper directly from a stamp.
Modern lithography is a relatively complex process that uses several different materials. The original image is etched on a flat surface. Usually it is aluminum, plastic or zinc sheets. From here and the name of this type of a print - a flat offset printing. Further, in a special way, the drawing is transferred to a special roller covered with an elastic rubberized fabric, which is part of a complex structure - the printing unit. And only after that the drawing is transferred to paper, plastic or film.
The offset printing method is, therefore, a special method of transferring images from a solid form to paper or polyethylene. It includes such steps:
The engraved plate cylinder is in contact with a roller moistened with water, whereby it is moistened.
Next, the form is in contact with the rolling shaft, which is part of the inking unit. Since the mold is already wetted with water, the paint adheres only to the engraved areas.
In the next step, the plate shaft touches the offset sheet of the cylinder, painting it, and from here it goes to paper or film.
This technology allows you to get very high-quality images with many small details. After dyeing, the paper or film enters the drying machine, and then - for final processing (cutting, pasting finished products, etc.).
The technological process at all stages of the work in the printing house is followed by a person of a special profession. Such an employee is called “offset printing printer”. What is this profession and what is its specificity, easy to guess. The specialty of a printer assumes that a person has above all such qualities as good artistic taste, a developed sense of form, and a long-term figurative memory.
Drawing multi-color images
Offset printing is, as you can see, a rather technologically complicated method. In this case, the method described above can also be called the simplest and cheapest. There are much more complex offset printing technology. According to the considered methodology, as it was possible to notice, only monochrome images are obtained. In order to print more complex drawings, the so-called technology of four colors is used. In this case, different colors are created by mixing the main ones: cyan, magenta, yellow and black. For their designation is used the abbreviation CMYK.
The machines used for multi-color printing have four sections. Sometimes used and five-piece equipment. 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 marked. 4 + 4 - what is this designation, for example? The answer to this question is simple. Thus mark products with offset printing applied on both sides. In other cases, the notation is decoded 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 black-and-white drawing on the reverse side of the sheet.
By type of source material in printing houses, there are only two main methods of offset printing: sheet and roll. They differ primarily in performance and quality. In the first case, already cut paper is laid in the machine, so the printing of images is very slow. But the drawings themselves are obtained with the highest quality.
Web offset printing is a technology in which a very long ribbon of paper or film wound onto a shaft is loaded into a machine. The process of image imprinting in this case is continuous.
There are also such methods of drawing a picture, as a deep and high offset printing. In the second case, the print is obtained due to the pressure on the paper protruding (high) parts of the engraving. The second method is technologically somewhat more complicated. When used, the paint fills the recessed parts of the engraving. The drawing on the paper in this case is also transferred on contact, but without pressure. The whitespace areas are simultaneously cleaned with a special tool, the squeegee. This technique is used in printing houses most often. The fact is that by adjusting the depth of the engraving you can easily make halftones and widely apply the technology of light and shade.
The offset printing is first of all the technology allowing to receive very effective images at the minimum expenses. Figures applied using this technique, have seen, of course, all without exception. For example, in this way logos are applied on commercial plastic bags.
Also some companies practice offset printing of business cards. What it is, probably everyone understands. On the pieces of thick paper or plastic are applied. position and other information about any person. Offset printing allows you to get very beautiful business cards in any colors. You can use a variety of design styles.
A feature of this technique is, among other things, that it allows you to apply beautiful drawings with fine details, even on a not too high-quality carrier. After all, the main printing element in the sections is covered with rubberized elastic fabric. Therefore, the paint fits very well even on a not too smooth, rough surface.
Offset printing paper is, however, a product having some special qualities. Typically, this material is made from white environmentally friendly cellulose. The main feature of this paper is high density. The fact is that on too loose sheets of paint begins to seep on the opposite side.
Recently, another method of printing images, digital, has become widespread. The offset printing is the technology allowing to receive very high-quality drawings. However, the digital technique is considered even more perfect. Its advantages are not only in the highest image quality, but also in mobility and print speed. To produce with its use, for example, the same business card can be directly in the presence of the client.
The cost of digital printing ultimately turns out to be somewhat lower than that of offset. However, this method is usually used for the production of printed products only in very small quantities. This is due primarily to the features used for printing equipment. As the name implies, images are printed in this case using printers of various designs.