Types of printing process

1. The Gravure process is a type of intaglio process in which the actual image is etched into the surface of a plate or metal cylinder. The image consists of tiny cells (or wells) engraved into the cylinder; there may be as many as 22,500 ink wells per square inch. When the cylinder is rotated in a fountain of ink, the excess ink in the non-image area is removed by a thin piece of stainless steel called a doctor blade. The size and depth of each ink well determines how much ink will be deposited on the substrate. When paper is passed between the plate cylinder and rubber impression roller, it acts like a blotter and absorbs the remaining ink in the microscopic wells.

In gravure printing there are sheetfed and webfed (rotogravure) presses. Sheetfed gravure is targeted at limited production runs of fine art prints, high quality art, photographic books, advertising leaflets, and higher denomination postage stamps. Rotogravure is targeted at larger runs of 300,000 copies or more and includes weekly or monthly magazines, mail order catalogs, specialized packaging, wallpaper, and some decorative laminates. Both presses require plate-making (or cylinder engraving) and proofing, which is often very expensive. Color corrections and last-minute changes often require cylinder retouching, and this can sometimes be slow and very time-consuming.
The print quality of photographs using gravure is often superior to other printing processes. Both press configurations are direct printing, so ink-and-water balance is not a variable for controlling image density. The inks are either petroleum-based or water-based, and the use of electrostatic assist allows for better ink transfer on substrates with hard surfaces and poor ink absorption. Gravure gives a true halftone effect where photographs tend to have greater contrast and detail due to heavy ink films and use of finer screen rulings. Because of the cell structure, fine details in type-matter and line-work are of critical concern. When using type styles containing serifs, it is advised not to use type sizes smaller than eight point. Overall, gravure is great for long runs (300,000 or more) and capable of maintaining color consistency on a wide range of substrates.

Advantages
The rotogravure printing process is the most popular printing process used in flexible-packaging manufacturing, because of its ability to print on thin film such as polyester, OPP, nylon, and PE, which come in thicknesses of 10 to 30 micrometers.
Other appreciated features include:
printing cylinders that can last through large-volume runs without getting worn out
good quality image reproduction
low per-unit costs running high volume production

Disadvantages
Shortcomings of the gravure printing process include:
high start-up costs: hundreds of thousands of copies needed to make it profitable
rasterized lines and texts
use of chemicals in the ink.
·         Every morning this week, I’m running a series of guests posts about different printing methods – so if you’ve ever wondered why certain printing methods are best for certain kinds of designs (or cost more than others), this is for you!  You can read the previous installments covering digital printing, engraving, screen printing, letterpress printing with antique type, and foil stamping all right here.  Today we’re talking about offset printing, with help from Katie of Kelp Designs and Nicole of Barrington Printing.

2. Offset printing is often confused with digital printing – both are four-color flat printing methods, but the process is quite different!  While offset printing is incredibly common, the printing process and procedures are often not well known.  Barrington Printing, a family-owned print shop in Cranston, Rhode Island, provides offset printing to a range of clients around the United States, including Katie of Kelp Designs in Los Angeles, California.  Katie recently interviewed Nicole about the offset printing process.
·         Offset printing is one of the most common flat printing techniques, wherein ink is transferred from a plate to a rubber blanket, then back to the printing surface.  Like most types of printing, offset printing is a mix of art and science.   Although the process is very technical (the science part), the press operator also carries a lot of weight in achieving the desired outcome of the printed piece.
·         Offset printing (or lithography) is what you probably see most often in your day to day travels.  It is often used for direct mail postcards, business cards, brochures, pocket folders, signage and, yes, greeting cards and stationery.  Offset varies from other print methods in many ways including technology, process, cost, material options and turn around time.

Source: Internet