Offset
Offset printing offers superior print quality to digital printing because of its ability to reproduce more accurate and vivid colours, using specific Pantone colours. The offset printing process is based on the principle of repulsion between water and fatty ink. The process takes place in several stages, which you can explore below.
The stages of offset printing:
Plate preparation: first of all, a thermal printing plate (PS) is made using an imagesetter (CTP) for each colour used in the final image. The areas to be printed are treated with products that make them hydrophobic (water-repellent) and oleophilic (ink-attracting). Areas that are not to be printed are left intact and retain their hydrophilic (water-attracting) characteristics.
Printing: when printing, the printing plate is mounted on a printing cylinder. Water is then applied to the plate and is repelled by the hydrophobic areas that have been previously prepared, leaving only the hydrophilic areas exposed. Ink is then applied to the plate and is attracted to the oleophilic areas, leaving no trace of ink on the hydrophilic areas.
Image transfer: the printing cylinder with the printing plate is then pressed against the sheet of paper, transferring the image onto the sheet.
Repeat: this process is repeated for each colour used in the final image, using a different printing plate for each colour.
Finishing: once all the colours have been printed, the sheet of paper is dried and can be cut to obtain the final product.
Offset printing is particularly suited to large quantities with high colour accuracy, making it ideal for jobs requiring vibrant, rich colours.
Digital vs. offset printing :
- Cost: digital printing is much more economical than offset printing. This is due to the high initial costs involved in setting up an offset press.
- Quality: offset printing offers far superior print quality, particularly for large print runs. Colours are more accurate and vivid due to the use of specific Pantone colours. Digital printing can also offer good quality, but may lack the sharpness and colour accuracy of offset printing.
- Production time: digital printing is faster and more flexible than offset printing, as it does not require printing plates and can therefore be quickly set up and modified for immediate printing. Offset printing takes longer to prepare the plates, but once the press is set up, it can produce high-speed prints.
- Media types: digital printing can print on a variety of substrates, including cardboard, film and self-adhesive media. Offset printing is better suited to paper substrates, particularly high quality papers, as it offers greater precision in printing and colour.
- Print resolution: the offset printing process can achieve extremely high resolution because the printing plates are exposed at 2400 dpi or more. Although digital printing is constantly improving, it can still make a difference when using very fine fonts such as those found on some business cards.
- Positioning accuracy: offset presses have sophisticated gripper systems and are extremely precise when guiding the paper. This means that the printed image lands in exactly the same place from one copy to the next. This is important for subsequent finishing, such as embossing, or when cutting out delicate designs, such as business cards with printed frames.
In conclusion, digital printing may be preferred for less prestigious substrates, but its advantage is undeniable when it comes to personalised work and fast production times, whereas offset printing is better suited to high-end results or high-quality work.
Spot colour printing
Direct tone printing is the printing technique we use in our workshop. It involves applying the inks we use, which we premix according to standardised formulas, such as the Pantone Matching System (PMS). Each PMS colour has a unique identification number, which allows us to obtain a precise match of the desired colour. Unlike four-colour process printing (CMYK), which uses the four basic colours (cyan, magenta, yellow and black) to reproduce a wide range of hues, spot colour printing uses ready-to-use inks that correspond to specific colours. This technique is best suited to situations where specific colours need to be reproduced accurately. It allows you to obtain vivid, precise colours without depending on the mixing of base colours.
Printing in CMYK
In the workshop, to produce CMYK offset printing, we prepare the files in four-colour process mode (cyan, magenta, yellow and black). We then create printing plates corresponding to each CMYK colour. After preparing the offset press and inking the plates, we transfer the ink onto rubber blankets and then onto the printing substrate. Finally, we dry the ink to ensure accurate colour reproduction. This process is repeated for each CMYK colour.
Four-colour printing uses four ink colours (cyan, magenta, yellow and black) printed in the form of millions of tiny superimposed dots that mix to create the full spectrum of colours. Also known as the CMYK process, this printing method saves money by limiting the number of printing plates needed for a job to four. But there are some limits to the specific colours that CMYK inks can create.
