Planographic1875
Offset Lithography
The workhorse of commercial print.
An inked plate transfers (offsets) the image onto a rubber blanket, which then prints onto paper—billions of pages a day.
Ink jumps from a metal plate, onto a rubber roller, then onto paper.
- ▸The middle rubber roller is what 'offset' means — it never touches the plate-and-paper directly.
- ▸The rubber smooths out the image so it lands cleanly on rough paper.
- ▸This is how almost every magazine and book is printed today.
History
Robert Barclay adapted lithography for tin in 1875; Ira Washington Rubel applied it to paper in 1903. By mid-century offset displaced letterpress as the dominant commercial process.
Process
- 01
Image-set CMYK plates from digital files.
- 02
Mount each plate on a cylinder; dampen and ink it.
- 03
Plate transfers ink to a rubber blanket cylinder.
- 04
Blanket transfers ink to paper passing through.
- 05
Repeat across four (or more) printing units for full colour.
Strengths
- +Highest quality at scale
- +Cheap per copy at volume
- +Sharp halftones
Limitations
- −Setup cost (plates, makeready)
- −Not viable for short runs
- −Industrial footprint
Sources & citations
References for the history and process described above.
- 01Offset Printing — Encyclopædia Britannica
- 02Ira Rubel and the Accidental Invention of Offset Lithography — Smithsonian Magazine