Offset Printing Technology for Custom Boxesadmin
What is Offset Printing? A Detailed and Overview
Offset printing (or offset lithography) is a dominantly used commercial and industrial printing technique, which is favored over other printing techniques, particularly due to high image quality.
The offset printing technique employs plates to transfer image to the receiving media (usually paper). It is an indirect printing method in which the image is not directly printed on the paper but is printed indirectly from offset metal plates via a rubber blanket roller. The offset plate, on which the image is initially transferred, is chemically treated in such a way that upon the application of ink and water on it, only the ink adheres to the image and text areas. These areas repel water. Contrarily, a thin water film forms on the blank areas (which does not have images or text) of the plate which repels ink. The inked image is then moved from the plate to a printing rubber blanket, which then transfers it to the paper. This procedure is repeated on every paper (or any other receiving medium) that moves through the printing machine.
For full-color printing, the paper is overprinted four times on four separate printing units with different colors. Offset printing utilizes a “four-color” or “process color” model known as CMYK, which refers to the color plates used: cyan, magenta, yellow and black (the black key plate). Now, this does not mean that we will get only these four colors in the printed images. We will get a colorful image as these colors combine to give a variety of different colors.
Some related terms that you need to know
Now that we have known the basic mechanism of offset printing, let’s have a look at some of the terms that are associated with it.
- Aqueous Coating: It is a water-based coating that is meant to protect and intensify the printed product. It gives a glossy look, smoother feel, and durability to the printed pieces to protect them from dirt and damage.
- Chromo Paper: This coated paper has a coating of rag paper or wood pulp on one side.
- Color Management System (CMS): CMS is a collection of software tools that coordinates devices like monitors, printers, scanners, and printing machines to ensure color uniformity and consistency from the beginning to the end of the whole printing process.
- Duplex Board: It is a multilayered paperboard having a grey-colored middle layer and a grey back woodfree coated on one side.
- Fountain Solution: This solution is also known as dampening solution. It contains water mixed with chemicals and is used to wet the offset printing plate. The function of this solution is to keep the non-imaging areas of the plate clean and free from ink.
- Impression Cylinder: Impression or printing cylinder presses the cardboard (or any other receiving medium) on the blanket cylinder so that a solid colorful impression is printed on the printed product. It rotates in a direction that is opposite to that of the blanket cylinder, and these opposite rotations are responsible for the transportation of the cardboard between them for printing.
- Ink Volume: The quantity of ink, which is applied for printing, is a crucial factor for obtaining the wanted impression.
- Raster: The ink volume depends on the raster. Raster is a series of parallel lines that describe the number of lines per vertical (in centimeters) and the slope of lines (in degrees angle). Raster graphics are the image files formed by individual dots or color pixels and are created digitally. A raster is a grid having X and Y coordinates, and a raster image tells which coordinates are to be illuminated in monochrome or color values.
- UV Inks: UV inks can be bolder and brighter than the traditional offset printing inks due to the reason that there is practically no dry-back. These inks are exposed to UV light after they are transferred to the surface that is to be printed. This exposure results in the polymerization of colors, which hardens the ink. Basically, photo initiators are present in color due to which it polymerizes quickly, and that is why the ink dries immediately upon exposure to the UV light.
Some of the basic advantages of using offset printing technology
As mentioned earlier, offset printing techniques have more advantages in comparison to other printing techniques. The most important thing for a printing technique is to give long-lasting and excellent quality print, and this technique gives great results in this regard. The final print quality is outstanding, and as the rubber layer sticks to the printing medium, clean and precise illustrations are obtained.
Another advantage of this technique is that its printing plates are quite durable. The main reason for this is that the printing plates do not come directly in contact with the printing medium. This means that these plates usually last for a longer time. Furthermore, these durable printing plates have fast and simple construction.
Lastly, it is the fiscal factor. This technique is quite cheap which means that we can get excellent quality prints in relatively less amount of money. This makes it quite suitable for industrial printing.
Weaknesses of offset printing technology as compared to its competitor technologies?
Despite offering some advantages, this technique exhibits some weaknesses and limitations too. One of these is the limitations of the time. Setting up the offset printing machine requires time and energy. Furthermore, the printing plates must be settled before being put in the machine. This means it is very much likely that you would not be able to get instant results in case you are in a hurry. In such a situation, digital offset is a better option.
One more issue with this technique is the sensitivity of the plates. Sometimes a chemical reaction may render the plates sensitive, leading to the printing of non-image areas. This would affect the print quality of the final printed product.
Although the offset printing gives excellent quality prints, the quality is still a bit low when compared to the rotogravure printing.