Offset printing is suitable for medium and large jobs that require high quality printing. The offset printing process is indirect (as the name suggests, off set), i.e. the image is transferred from a matrix (plate) to a printing roller (the cautchu) and then to paper. The offset printing plate is usually metallic (made of aluminium) and light-sensitive. In the traditional process, the engraving starts from a photolitho, which is placed over the offset plate and exposed to the light for image fixation. After the exposure, the matrix is sent to a developing process, very similar to the photographic developing process. Subsequently, this flexible plate is mounted on the cylinder destined for it. If the work is coloured, a plate is required for each colour of the four-colour process (CMYK), requiring the use of, at least, 4 plates. The cylinders of the offset machine guide the ink and paper in a linear flow. The ink is transferred to the plate and, although the plate is completely flat, the pigment only adheres to the area with the printed image. The water used in this process repels the ink, and there is a combination of water and grease (offset ink has a greasy consistency). The matrix transfers the ink to the cylinder (made with a kind of rubber) and this cylinder transfers the image to the paper. The process of indirect printing seeks to maintain the paper dry and also to extend the life of the plate. Both flat offset printing machines and rotary printing machines follow this process. The difference consists only in the paper, that can be in reel or sheet-fed, and in the inks (conventional or ultra-violet). Nowadays, analogue processes are no longer so widely used, giving way to CTP’s (Computer-to-Plate), which speed up the process and generate less material costs. Computer-to-plate is the production process of the plates used in offset printing. The plate is engraved by a laser, which is controlled by a computer, allowing the plate to be generated directly from a digital file, without the need to produce an intermediate photolitho. This process also guarantees an increase in the final quality of the engraved image.

It is a very old printing technique that has evolved over the last few years. It is no longer only executed manually, but whose process logic remains the same. Initially the photolithos (also referred to as negatives or acetates) are printed, which are the intermediate support between the initial image and the final image. The mesh can be reused as many times as it can hold, after cleaning the previous information with an emulsion. A photolitho is made for each colour that makes up the image, but the photolitho is always printed in black. It must be taken into account that all colours must match 100% at the time of printing. Next, the screens are developed. These are made up of a metal frame which stretches a nylon mesh at its centre. By means of a photosensitivity process, the photolitho (containing the black image to be printed) is placed on a UV light table under a screen prepared beforehand with a sensitive to light emulsion. The image on the photolitho is recorded on the nylon mesh, which is where the ink transfer occurs. The rest of the mesh is sealed by the hardening of the emulsion that was exposed to the light. The meshes can vary in the opening of the filaments which compose the nylon, influencing the amount of ink that is transferred through the openings, or the height/relief of the print. Subsequently, this emulsion is removed from the screen printing to start placing the ink on the frame and the final print. In screen printing, it is necessary that each colour is engraved on a different frame (one frame per colour is used), so that when they are all printed together they form the final coloured figure. Screen printing is a repetitive printing system, since the aim is to reproduce the design as many times as necessary without ever losing definition. In the industrial printers, this process is done using their own printing machines, which automate and speed up printing for larger quantities. Just as in offset printing, CTP (Computer-to-plate) is also used in the industrial screen printing process.

A digital print is when the print has as intermediary only the information received by a computer. In other words, to transfer the data from the computer to the paper, it is not necessary to create a plate or a frame. For a long time, it was printed only from plates, as in the case of offset printing, or from frames, as in the case of screen printing. Although offset printing or screen printing offers a great printing quality, it can be quite expensive for those who want to make a small quantity of prints, besides being more time consuming processes. The need to create the photolithos, the assembly, the engraving and developing of the plates, among other costs, makes the speed, allied to quality, of digital printing gain more and more importance.

Flexography is a printing process in which flexible plates with a relief in a kind of rubber (cliché) are used. It also uses inks and varnishes more liquid and fluid (water-based, or solvent-based, or UV), which dry quickly through drying evaporation or UV. This enables printing, not only on paper, but also on non-absorbent materials, such as polyethylene, aluminium, plastic, among others, in special rotary machines. The area of the image that is to be printed is what appears in relief, so it is the only element that comes into contact with the ink. The ink is transferred directly from the plate onto the chosen support. Flexography is a printing process used for products with large print runs and simpler and less elaborate technical printing characteristics. However, the print quality, in certain jobs, is almost comparable to offset printing. It should also be noted that this printing system only exists on reel.

This is the oldest printing technique and has been progressively replaced by other printing systems, namely offset. It uses typographic characters, or clichés, which are composed in two moments: composition and printing. In this case, the printing matrix is hard and flat, normally metal (plates), on which the image to be printed is in high-relief. The cliché is fixed by means of a special adhesive on a surface in the printing machine: the part engraved with the high-relief images on the cliché receives an ink layer from an inked roller, and the ink which remains impregnated on the cliché is transferred under pressure to the paper. The performance of these machines is lower than others, and their use is currently directed at projects with simple characteristics and without large print runs.

This is a printing process using indirect ink transfer from an embossed cliché with the motif to be printed, using a kind of silicon “pad” that moulds itself to the shape of the object. This printing system allows any design, word, symbol or photograph to be printed in high definition and with great precision on all types of irregular, concave, convex or flat surfaces, and is used mainly for printing small areas and details, usually on merchandising products. This printing system only exists on a flat surface and is not possible to print on a reel.

Thermal transfer printing uses a thermal head, a coated ribbon and a media. The print ribbon passes underneath the printhead, which contains ink and heat. This heat results in the ink being transferred onto the label. Once the ink is transferred onto the substrate, drying is almost immediate. Thermal transfer is the preferred printing technology for marking variable information on rigid and flexible packaging or labels: barcodes, logos, stock control, expiry dates, or batch numbers. This data is important for identifying a product, ensuring its traceability, but also for providing essential information to the consumer. The materials used are varied, from simple coated paper, to synthetic materials or textiles. The final printed product is quite resistant and durable, depending on the tape used and the label material, and it can be exposed to different temperatures and factors such as humidity or dust.

Inkjet printing uses a print head with numerous orifices, which sprays thousands of ink droplets per second, and is controlled by technology that determines how many drops are to be sprayed onto the print media (paper, film or other substrate), and where, of a particular job. The ink is generally stored in two ink tanks, one black and the other with three colours (cyan, magenta and yellow), but there are also inkjet printing machines which include black and other colours in a single ink tank, or use one ink tank for each colour. The final colours are always formed from the mixture of these 4 CMYK colours. There is also 6-colour printing, where light cyan and light magenta are added, in order to achieve a greater accuracy in shades. The definition always depends on the printing machine technology and the quality of the ink.