Offset Printing Process: How Does It Work?
What is Offset Printing?
Offset printing is a popular printing technique used worldwide for the professional and precise printing of high-volume items such as stationery, magazines, books, and catalogs. Also known as offset lithography, it is a highly eco-friendly and cost-effective process that ensures speed and quality.
Unlike other printing methods, which print directly onto paper, offset printing includes printing onto a rubber plate first and then onto paper. The 4-color process is a popular coloring technique used to print sharp full-color images. This process utilizes cyan (C), magenta (M), yellow (Y), and black (K) inks which are layered on top of each other by separate plates to create the most delicate color prints, with the color range encompassing as many as a thousand colors. CMYK printing is currently the most common method used in printing process for commercial items, especially in offset printing process.
How Does Offset Printing Work?
This printing process is called ‘offset’ because it adds a step to the traditional printing process; instead of printing directly onto paper, offset printing prints onto rubber plates which then print onto sheets of paper. This step ensures minimal wear and tear on the plates, increasing their lifespan. Moreover, it conforms to the surfaces of textured papers.
Offset printing process makes use of 3 cylinders, namely:
- Plate cylinder
- Offset blanket cylinder
- Impression cylinder
Pre-Press
Pre-press refers to the process that precedes the printing. The plate cylinder is involved in the plate-making step. During this step, the plate, made of plastic or aluminum, is customized based on the design that needs to be printed.
The customized plates are mounted onto the rollers in the offset printing press, with one plate of each color in the 4-color process (CMYK). Each plate of one color is layered on top of the other which will result in sharp and realistic final print.
Press
The plates are then passed through water rollers, dampening them thoroughly. In places where color needs to be printed, known as the image area, the plates are pre-treated to repel the water, leaving them dry and the non-image area of the plate wet. Then, special vibrating ink rollers apply thick oil-based ink onto the plates.
Offset lithography functions on the principle that oil and water don’t mix. Because non-image areas are wet, the color does not stick to them, covering only the remainder areas.
The second cylinder, offset blanket cylinder, has a thick rubber roller that prints the image from the plate cylinder onto itself. Both cylinders roll against each other in opposite directions as the water is squeezed out, printing a mirror image from the plate roller onto the plastic roller.
In the last step of the offset printing process, the impression cylinder is used to print the image onto the final paper sheet. The cylinder passes sheets of paper through the plastic roller, moving in the opposite direction of the offset blanket cylinder. The images are printed onto the sheets at the exceptional rate of 5 sheets per second.
Post-Press
After the sheets are printed, they are sent for finishing, also known as post-press. Post-press entails either adding gloss or matte laminations onto the sheets and sending them for trimming, folding, and binding, depending on the print type.
Offset printing presses are popularly fast and efficient. One press can print up to 18,000 sheets in just an hour, each containing 48 A4-sized papers, adding up to 120,000 pages, making offset printing ideal for large batches.
Types of Offset Printing
There are two ways in which offset printing is done.
The first type is sheet-fed printing, which involves printing on individual sheets of various sizes. Sheet-fed presses are best for printing marketing materials like billboards, advertising cards, and fliers.
The second type of offset printing is web-fed printing, wherein large rolls of paper are used in a continuous length. Web-fed presses are used primarily for printing catalogs and magazines.
Advantages of Offset Printing
There are many advantages of offset printing, especially for commercial purposes.
Speed
One significant advantage of offset printing is its speed and efficiency for large batches. In the case of newspapers, printing large numbers is required daily. Offset printing warrants high-quality material in less time. In contrast, digital printing not only is slower but it doesn’t print large batches either.
Cost-Effectiveness
As a close second advantage, the cost-effectiveness of offset printing makes it a highly desirable option. The more printed product, the cheaper the prints get as the sheets only cost a few cents. For example, billboards which are placed all over the world in large quantities. Offset printing makes certain that marketing becomes as cheap as possible.
HQ Finishing
Because offset printing uses CMYK printing, many custom finishes become possible, opening up multiple avenues for creative, colorful designs. Different kinds of custom inks are also available, from metallic to fluorescent, adding more attraction. Printed items such as magazines use various types of designs and colors. Dulled-out prints reflect poorly on the company, which is why professional-looking printing is required.
Inexpensive Printing Plates
A custom-made printing plate is required for each print job. With the technological advancements in this day and age, the plates are comparatively cheaper and simple to make and can be used a million times approximately.
Sharp Details
Lastly, offset printing produces sharp and fine details coveted for marketing purposes. The more professional the print appears, the better it will be received by its audience. That’s why for brands, printing catalogs and brochures in high-quality prints with precise attention to detail are highly preferable.
Conclusion
Offset printing process uses advanced technology, producing cost-effective and professional prints for established brands that require sharp and professional-looking finishing. Unlike digital printing, which can be slower and may not result in the desired high-quality prints, offset printing is a feasible option for high-volume items and brand images.
Sejahtera Inti Prima is a one-stop solution for all your printing needs. With a portfolio of over 16 partners and 30-year of experience, rest assured that SIP Printing will exceed all your expectations by providing you with our best services, including consultation, planning, and pre-production. Contact us today for a consultation that will forever change your brand’s image!