Gravure
Gravure printing is an example of intaglio printing.
It uses a depressed or sunken surface for the image. Gravure image
areas consist of cells or wells etched or engraved into
a copper cylinder, and the unetched areas of the cylinder
represent the non-printed areas.
History:
The origins of gravure printing were with the creative artists
of the Italian Renaissance in the 1300s. Fine engravings and etchings
were cut by hand into soft copper.
The engraved surface consisted of channels or sunken areas. The Italian word
intaglio (in-tal-yo) means engraved or cut in.
Intaglio refers to a method of printing whose image carrier consists of lines
or dots recessed below the surface.
Intaglio reproduces an original design by pressing paper into the recesses.
The first intaglio plate was used for printing in Germany in 1446 about the same
time as Gutenberg. Unfortunately, the intaglio process was not compatible
with Gutenberg’s letterpress, so it wasn’t adopted by early printers.
The modern gravure printing press resulted from the invention of photography
and the adoption of rotary printing from cylinders.
William Henry Fox Talbot invented the halftone screen in 1860, as a method of
breaking up continuous tone images into a series of discrete dots.
This method is used to reproduce photographic images in all printing processes.
Auguste Godchaux received a patent for a reel-fed rotary gravure perfector
press in 1860.
This press was still in use in 1940. The process was refined by the German Karl
Klic (Klietsch) and the Englishman Samuel Fawcett.
Klic and Fawcett didn’t have patents on their process, so they tried to keep
the process secret. They sold prints from their press as “heliogravure” prints,
even though they were really rotogravure as we know it today.
Their process remained a trade secret until an employee emigrated to the United
States and made it public.
The process continued to improve and gravure presses were used to print Jell-O
cartons starting in 1938.
Engraving continued to improve with electromechanical engravers being introduced
in 1968 with digital controls added in 1983.
<http://www.wmich.edu/ppse/gravure/pp2.htm>
The image cylinder rotates in a bath of ink called the ink fountain. The excess ink is wiped off the surface by a flexible steel blade called the doctor blade. The ink remaining in the 1000’s of recessed cells forms the image by direct transfer to the paper as it passes between the plate cylinder and the impression cylinder.
Three types of processes are used to make the gravure printing cylinders.
• Chemical etching: produces cells of the same
size or area with varying depths or cells with varying area
and depth.
• Electromechanical etching: produces cells that
very in area and depth
• Direct Digital Laser Etching: process which
uses a special alloy and lasers to produce cells of varying area and
depth at speeds 10-15 times faster then electromechanical etching.
Produces excellent reproductions of pictures but slightly ragged type.
The high cylinder-making costs make it limited to long-run printing.
It is used for newspaper supplements, magazines, catalogs, wallpaper, and packaging.
http://en.wikipedia.org/wiki/Rotogravure
http://www.pneac.org/printprocesses/gravure
