In order to classify offset printing, two main categories are used, with their subsections. Offset printing is distinguished by the presence or absence of humidification in the production process (in more detail below) and by the type of media used in the process.
In terms of moisture, offset is distinguished:
In terms of carriers, they distinguish:
- rolled;
- sheet;
- narrow format;
- widescreen;
- full-length.
Let us analyze in more detail each of these varieties and describe the features of each offset printing option.
Traditional offset or humidified offset
This option for creating printing products is considered classic. Offset humidification for this period is the most common in printing houses around the world. Although in the future other printing technologies may well become more common, after all, some improvements are constantly being created in this area.
For printing, special printing forms are used, which are filled with blanks and printed elements. Simply put, where the letter or sign is located on the final product, this symbol is located on the printed form, and where you need to make a space or free space, white space elements are located.
Printed elements attract dyes, whitespace attract water. This process is automated and uses special printing plates, which are issued by specialized enterprises. Such forms are the most common and have a lower cost compared to forms for dry offset.
Dry offset
A relatively new technology created by Toray Industries (Japan) in 1982. Technologically, the process of dry offset is a little more complicated, although in a certain sense it facilitates the tasks of printing workers. In particular, the printing process does not require control over the ratio of water to ink in the fountain solution.
White parts here stand out with silicone inserts on a printed form. Such forms are less common, but the main difficulty is the search and purchase of dyes for dry offset. These dyes are made according to a laborious recipe and a limited number of manufacturers.
Now let's move on to the classification of offset printing by media used. Under the carrier here is meant the material on which the final image from the printing form is applied.
Roll offset
The carrier here is the so-called roll, that is, a roll of paper of a rather large size. First, the paper passes under the printing form in a roll and only then is cut into a certain size and folded.
Roll devices, as a rule, are installed only on large printing houses. Such equipment is very expensive and therefore is cost-effective only for large firms. For the most part, only large runs are performed on roll units.
Sheet offset
As it is not difficult to understand, here the carriers are separate sheets. There is a pair of cylinders on which the printing plate is located, each individual sheet is transferred there with the help of suction cups. After rolling, an impression appears with one or another image.
Ideally, immediately after the first rolling, a full-color print appears, but in reality many printing machines do not have the required number of sections. Therefore, the sheets need to be rolled through the cylinders repeatedly in order to obtain the desired image. Moreover, each time it is required to align the media in order to print in accordance with the template.
In addition, there is equipment with several printing sections. Such units are the best option for creating a multi-colored image. Rolling sequentially through several sections, the carrier acquires the corresponding colors in the desired sections of the canvas.
This variety is the most popular and is used to create the most diverse printing products:
- creating booklets for advertising and marketing;
- replication of periodicals;
- label printing;
- production of forms;
- preparation of annual reports;
- poster printing ( );
- making packages.
There are other varieties of printed products that are often made in this way offset.
Single format offset
For these devices, a web is used that has a transverse size from half a meter to 60 centimeters. For the most part, narrow-format offset, which is sometimes called half-offset, is used to create high-quality commercial printing products.
Large format offset
The canvas here has a significant size across, which ranges from 135 to 190 centimeters. The works are mostly super-large, the range of manufactured products is very diverse from creating maps to large-circulation magazines and newspapers.
Full-format offset
The canvas in diameter has a size of 84 centimeters to meters. Accordingly, it is quite possible to call this type of offset medium format. The range of products is diverse, here can be made:
- books
- periodicals;
- packaging;
- directories
- magazines.
It should be noted the use of a method that allows you to increase equipment performance when creating logs. During the printing process, two rolls are sealed at a time. Next, these rolls are connected using a folding machine and, as a result, are compiled for the magazine in the desired sequence.