Offset printing is a highly efficient way to produce large volumes of flyers, brochures, newsletters and other printed materials. It's perfect for businesses looking to make a big impact on the market with print marketing pieces.
Essentially, offset printing uses special plates that are plated with images that attract ink and water. Then, the plate is transferred to a flexible rubber sheet and then onto paper.
Plates
Offset printing plates are the key to transferring an image to paper, cardboard or other materials. These are used to print high quality graphics and images on a wide range of substrates, from plain paper to vinyl and more. Plates can be made from metal, plastic, rubber or paper. The images are etched onto the plates with photo-chemical, photo-mechanical or laser engraving processes.
The cost of offset printing plates is based on a variety of factors, including the type of material, the number of colors and the size of the job. The more colors you use, the more plates will be needed to complete the job.
Xerographic (or electrostatic) transfer plates were first developed from the principle that certain insulators in the dark become conductors of electricity when they are exposed to light. The positive charge on the selenium plate attracts a fine powder which then becomes a conductive element in those areas touched by the light.
Blankets
Blankets are a key component of offset printing. They perform multiple functions – acting as shock absorber, ink-receptive and ink-release. To achieve these functions, the blanket surface needs to be smooth and uniform. A rough or uneven surface can cause ink to slur or smear and lead to less than ideal print quality.
Another factor that affects blanket performance is thickness loss. Stable fabrics and compressible layers can control this to a certain degree, but many blankets lose as much as 1.5% to 3% of their original thickness.
To prevent these irregularities from affecting the press, printers use analog-type "needle" instruments to measure on-press blanket/packing thickness. However, these needles can pierce through the blanket and expose spots of swollen packing material below it that may affect the printed image.
Cylinders
Cylinders are integral to the offset printing process. Each cylinder is used for a specific task. The first cylinder is the plate, which consists of a printed image. The plate is treated to attract certain inks while repelling other inks. Once the plate is positioned, the cylinder is then rotated. As it spins, the ink from the plate is transferred to the rubber blanket.
Next, the blanket cylinder receives the inked image from the plate and transfers it to paper. Finally, the impression cylinder presses the paper against the inked press blanket. All of these cylinders need to be properly aligned and lubricated. This is a complex task and requires skill and precision.
Inks
Inks are the primary components used in offset printing. They are formulated with additives that influence the runnability of the ink on a press, including body, temperature stability, length, tack, adhesion and drying.
Specialty and functional inks are becoming increasingly popular to address a wide range of needs from brand identity, to packaging and product protection. They also allow brands to achieve their sustainability goals and minimize the impact on the environment. Moreover, the quality of offset inks can make or break a print job. Inconsistencies can occur in CMYK process colors or spot color bases, and it is important to ensure that inks meet specifications.
For example, thermochromic inks change color or transparency when exposed to changes in temperature. They are used in toys, battery indicators and other packaging products. Other types of specialty and functional inks include glitter inks, which contain metallic particles that rise to the surface after printing, reflecting light, and creating a metallic sheen.
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