The Offset Printing Process: How It Works

Offset printing (also called offset lithograph), is one of the most common commercial printing methods used today. It’s favored for its flexibility, excellent quality, consistent results, and efficient use of resources.

At Wallace Carlson, we’ve long used offset printing to produce some of the most beautiful (and successful) print products imaginable. Now, we’ve created this article to help you understand its specific advantages. We’ll walk you through how your offset print products are made in our shop, and discuss why this method is so effective at helping you achieve your print goals.

The Basics of Offset Printing

To understand offset printing, you first need to know the difference between ‘direct’ and ‘indirect’ printing processes.

Direct printing is the simplest form of printing. If you’ve ever used a rubber stamp to mark a piece of paper, that’s direct printing. The image carrier, usually a plate or block of some kind, features a reversed version of the final image. After the ink is applied to the image carrier, the carrier is pressed directly onto the paper. When the carrier is removed, the final image is left behind.

Over time, it became clear to professional printers that direct printing on an industrial scale had serious drawbacks. For one, when the plate makes direct contact with the paper, it can lead to undesirable indentations and inconsistent image quality. It also leads to the printing plates wearing down faster.

So, around the start of the 20th century, indirect printing or offset printing methods were developed. In offset printing, a rotating rubber cylinder is rolled over the plate to pick up the ink and then rolled across the paper to create the final image. Today, thanks to its marked advantages over previous direct printing methods, many variations of offset printing are being used all over the world.

Step-by-Step Process

So, now you know the basics of how an offset printing press works. Next, we’ll look at the three steps for turning a digital design file into an offset print.‍

1. Pre-press: Preparation & Setup

‍The offset printing process starts by reviewing the design file and preparing it for conversion into cylindrical plates. Since the production of the plates represents one of the more significant upfront costs in a print run, it’s critical to check your work. Carefully proof all text and design elements before giving the okay. Once confirmed, a computer-to-plate (CTP) system will engrave your print information onto the cylindrical plates.

2. Printing Process

In an offset printing press, a trough-shaped component called an ‘ink fountain’ first coats a series of cylindrical rollers with ink. These rollers then evenly apply the ink to the printing plates. In turn, those printing plates roll against the rubber offset cylinders, which transfer the inked image onto the substrate.

Depending on the type of substrate you’re using (paper, cardstock, cardboard, etc.) and your desired final effect, the ink viscosity and printing pressure can be adjusted. Press operators can tweak each component of the press to ensure the final product is always of the highest quality possible.

3. Post-Press: Finishing Options

Finally, once the prints have been made, they can go through any required finishing steps, such as:

Trimming: This step is necessary for every offset lithography print run. A guillotine cutter is usually used since it can cleanly slice through many sheets of paper at once.

Coatings: This step adds optional aesthetic finishes to the print. Two of the most popular coatings requested by clients of Wallace Carlson are gloss and soft touch.

Binding: This step is used for multi-page publications. Binding options include saddle stitch, perfect binding, and spiral binding.

Applications of Offset Printing

Frankly, there’s no way to list every application for offset printing in a single blog. The variety is already too vast. What’s more, innovation-focused shops like Wallace Carlson are developing new applications every year. So instead, let’s focus on some of the most common and interesting applications, to illustrate this process’s versatility.

Newspapers and Magazines – Offset printing is the preferred method for periodicals because of its speed, accuracy, and vibrancy, even when used on very thin substrates like newsprint.

Collectibles – Offset printing enables products like trading cards and limited-edition artworks to be made with many desirable and eye-catching finishes.
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Packaging – Offset printing can quickly create large quantities of colorful, detailed, attention-grabbing packaging including cartons, labels, and product displays.
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Direct Mail – Offset printing creates crisp, consistent results, making it perfect for reproducing fine details and text in direct mail products like promotional flyers, postcards, catalogs, and more.