What are the common types of printing?

　　1. Letterpress Printing: This is a printing method that uses a raised printing plate (where the image and text areas protrude), commonly referred to as letterpress. The printing principle resembles that of a seal; early forms such as woodblock printing, movable-type printing, and later techniques like lead-type printing all fall under the category of letterpress printing.

　　According to the type of printing plate, common printing methods can be divided into four categories: letterpress printing, gravure printing, offset printing, and screen printing.

　　1. Letterpress Printing: This is a printing method that uses a raised印版 (where the image and text areas protrude), commonly referred to as letterpress. The printing principle resembles that of a seal; early forms such as woodblock printing, movable-type printing, and later techniques like lead-type printing all fall under the category of letterpress printing.

　　2. Intaglio printing: Ink contained within the recessed pits of the printing plate is directly transferred onto the substrate, commonly used for printing high-value securities such as banknotes and postage stamps;

　　3. Offset Printing: This is an indirect printing method where the image and non-image areas of the printing plate lie nearly on the same plane, utilizing the principle that oil and water do not mix.

　　4. Stencil Printing: Also known as screen printing, this is a printing method that uses a mesh screen as the printing plate. It can be used to create printmaking artworks, as well as for packaging and printing on everyday and industrial products.

　　II. Classified by Printing Principles

　　Based on the principles of printing, they can be categorized into two types: physical printing and chemical printing.

　　1. Physical Printing: In this method, the ink is applied as a physical buildup onto the raised areas of the printing plate, while the non-printing areas remain recessed or slightly raised—either lower or higher than the printed regions. Because these non-printing areas lack the proper surface texture to hold ink, they naturally stay blank. As a result, when the inked plate comes into contact with the substrate, only the raised (printed) areas transfer the ink onto the material, relying on purely physical and mechanical principles. Common examples of physical printing include letterpress, gravure, screen printing, and dry offset printing.

　　2. Chemical Printing: In this printing process, the non-image areas must continuously be replenished with a water-repellent, ink-rejecting film—this is known as chemical printing. Offset printing falls into this category; it involves adding a gum-like substance to the fountain solution, ensuring a steady supply of a mucilaginous layer rich in carboxyl groups. This mechanism helps prevent the non-printing areas of the plate from being contaminated by oils and greases.

　　3. Classified by Number of Printing Colors

　　Based on the number of printing colors, distinctions can be made as follows:

　　1. Solid-color printing: This isn’t limited to just black—any print that uses a single color qualifies as solid-color printing.

　　2. Multicolor Printing: Multicolor printing is further divided into three categories—additive color method, overprinting method, and process color method.

　　3. Color Printing: This refers to multi-color printing. All color prints—except for the very few cases using spot coloring or overprinting—are produced using process color methods.

　　4. Four-color printing: Typically refers to the printing process that uses the three primary colors—cyan, magenta, and yellow—along with black ink to reproduce color originals. It works by subtractive color absorption combined with additive color mixing, resulting in areas of color with relatively high lightness but lower saturation.

　　4. Classified by Printing Purpose

　　Based on the purpose of printing, categories include book printing, news printing, advertising printing, packaging printing, and special printing, among others.

　　1. Book printing: Previously, letterpress printing was used, but it has gradually been replaced by offset printing.

　　2. News Printing: Previously, letterpress rotary presses were used due to their speed and high print volumes. Now, to meet the demands of color printing, these have been replaced with offset or photogravure rotary presses.

　　3. Advertising Printing: Most materials—including color images, pictorials, posters, and more—are produced using offset printing, though letterpress, gravure, or screen printing methods are also employed in some cases.

　　4. Packaging and printing: Items such as candy snacks, packaging cardboard boxes, and decorative wallpapers are predominantly produced using photogravure printing.

　　5. Specialty Printing: Includes applications such as bottles and cans, gold stamping, embossing, flexible tubes, labels, and more—primarily utilizing specialized techniques or unique materials.