What is Offset Printing and How Does it Work?

Offset printing is one of the most common print methods. One of its many characteristics is that it works indirectly, similar to lithography; this means ink being transferred by pressure due to rollers instead of through inks on paper or other substrates placed directly onto a substrate sheet.

This method allows for large impressions and lowers production costs with each additional run, so it’s often very popular amongst printers.

To learn what offset printing entails and how it differs from digital printing, all you need to do is read our article here! 

What is offset printing?

The offset printing system is indirect. This means that the image is not printed directly on the media but rather through rubber rollers.

As we said, it does not go straight to paper or plastic, and for this reason, it’s called offset; instead, you pass your image through a rubber cylinder and then onto whatever final support material you need – paper or plastic.

The process begins with images being captured by cameras in digital form and various other sources such as photos from magazines and books, which are scanned into computerized systems where they can be manipulated digitally before being outputted via traditionally made prints of different sizes.

The printing system of the rollers is as follows: First, some rollers with ink, and others are dampers that bathe the areas of the illustration plate in which the image does not use ink – hydrophobic areas.

For this, a solution that repels it is used. Then, an oily ink roller applies oil to those wetter parts on top of those rough surfaces – where they would be imprinted by one color onto a metal alloy support plate-which has been previously engraved with images before being printed out using 4 or 6 plates, respectively according to CMYK colors while also taking into account hexachromia printers which require more plates than regular ones do (6 plates).

The plates are broken down into different colors. These plates are placed on the machine’s printing units. Specifically, they’re placed on the rollers.

The rolls, in turn, come in contact with dampers and ink-holders that contain only water or ink as needed to print a particular color of the image you want to be seen – due to their lipophilic (fat-loving) characteristic.

However, only one side of a plate receives color, while any other noncolored areas do not repel it so much as attract it instead. Once an area has received its required amount of ink or water desired by your design, it is captured onto rubber which then passes through four more rolls until finally reaching a heater for drying out before you get your final printed product.

Here: What is a printer?

Features of offset printing

Offset printing is used because it offers many advantages. The primary advantage of offset printing is that the image on paper almost exactly matches what was originally designed and created in the digital design process.

Features of offset printing

Another huge benefit to offset print production, which makes it so versatile, is that you can easily use both coated and uncoated papers.

Ultimately, despite some disadvantages to using this method over other methods like screenprinting or letterpress, its large variety of uses more than make up for any limitations.

  • Printing machines are divided into printing units. The product that comes out of the printer goes through several stages —or bodies— until the desired print is obtained. All printing units are equal to each other; however, what changes are the ink applied to them. In other words, each printing unit can only print one of the colors. In the bodies are the printing plates.
  • Printing offers better quality compared to direct printing on paper. This would cause much faster wear on the printing plates.
  • The scale used to print in four-color is CMYK colors (Cyan, Magenta, Yellow & Black), although other colors can also be used, such as special Pantone colors – such as gold or metallic colors. In addition to lacquers and varnishes – for this, the best printer needs to have additional bodies installed.
  • The printing order of the colors is as follows. Black comes first, then cyan, then magenta, and finally yellow. Yellow is the most transparent, so it also acts as a paper protector.

Offset printing formats

The offset printing formats are very varied. They support a large number of sizes and types of paper, with the most used sheets being those are measuring 52 x 70 cm; and 70 x 100cm. 

How It works

The offset lithography printing process uses plates and blanket rollers so that the oily inks adhere only to the portions of the plate where they need to go.

The ink is applied on a rubber-wrapped cylinder, which rolls over paper when it is brought into contact. Different presses use different plates and blankets for different run lengths or substrate requirements.

For example, some presses may print millions of sheets per hour. Web presses can lay down wide rolls of paper, going from one ink station to another until the process is completed.

This web press printer typically prints 10,000 or more copies in multi-page documents such as magazines and books.

Difference between digital and offset printing

Next, we will explain what offset printing and digital printing are. We will see the advantages and disadvantages of each type and do it in an easy-to-understand way – without technicalities so that people who aren’t used to the terms of graphic arts can understand.

Read Here: Types of Printers.

Number of copies

If you need just a few copies of what you are going to print, it is appropriate to do it digitally. What do we mean with just a few copies?

If it’s a book or catalog: from 4 to 300 or 500. If there is an event in more than one town and they have flyers, posters, etc.: between 100 and 2,000 depending on the size of the item being printed.

From 500 catalogs or 2,000 brochures – usually more appropriate for printing by offset because its price per unit is lower-prints can be made at faster rates as well (although this option will cost significantly less).

Urgency of work

Ink drying is an important factor in offset printing. Digital systems, like the ones described in this question, can take a long time to produce content because you have to generate plates and print them from scratch.

In contrast, digital printers are much faster than offset printers and don’t need that much ink for every page printed, making it better for big runs of books or magazines with lots of pages.

The number system mentioned by the student would be ideal for producing some 50-100 copies before doing more work on each one individually (using traditional means).

Print size

We will have to use offset printing technology to print a large poster or magazine, even if it is only a few sheets. In contrast, the digital sheet size is 33 × 48 cm, and thus we can easily print in high quantities with our digital printers.

Print media

Paper for offset printing comes in a wide variety of types and varieties. Over the past several decades, countless coated and uncoated papers, cardboard, laid paper, and embossed paper- these are just some examples of development.

The most popular options include PVC or digital printing on these materials. In addition to that, many other options exist, such as white ink (some may use this option), magnets, etc., while also using a range of colors like green/brown/black and different levels and thicknesses from matte to glossy.

Custom printing with variable data

Anything you can think of can be done with digital printing, including different types of covers and interior pages.

The combination of offset and digital printing can also produce variable data prints, such as printing the inside cover in offset but the catalog cover digitally on an e-reader.

Advantages and disadvantages of offset printing

Among the main advantages of offset printing we can mention:

  • Large runs can be printed inexpensively.
  • For large runs, it is faster than digital.
  • Provides excellent photographic quality.
  • You can use all kinds of papers: coated, laid, with textures.
  • Supports the use of special inks, Pantone’s, gold, silver, varnishes.
  • Larger paper sizes than digital printing.

Some of the drawbacks of offset printing are:

  • Machine setup is complicated and expensive.
  • Inks can cause repainting if not allowed to dry enough.
  • The work cannot be manipulated until after 24 hours.
  • There may be color instabilities during the roll.
  • All printed copies must be the same. It cannot be customized.

Last words of what is offset printing

We hope you find the answer to your question about offset printing. If your question has been answered and you have an opinion about it, please let us know in the comments below.

Thank you for reading us What is offset printing blog.

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