List of printing process used for printing postage stamps:
- Engraving (Also known as Etching, Line-engraving and Intaglio)
- Typography (Surface Printing; Letterpress; Flexography; Dry Offset; High Etch)
- Photogravure (Rotogravure, Heliogravure, Gravure)
- Lithography (Photolithography; Offset lithography; Stone Lithography; Collotype; Planography; Dilitho)
- Embossed printing (Relief)
Image from the Scott Stamp Catalogue (Introduction part), where you can find more complete information about each stamp printing process, including definition of terms like rotary press, re-entry, plate, die-cutting, double transfer, re-engraving, dropped transfers, short transfer, ink colors, stamp holograms, foil application, gums, reprints and much more.