Map Making Techniques
Below are some of the main technique which have been use for the production of maps and charts over the last 500 years.
Engraving
The Latin term intaligo which
means incise, applies to the printing techniques which result
in the
image being created below the surface of the plate.
The material used for forming plates up to
the early 19th century was copper sheet, this diminished after the
the invention of the
more economic mild steel. So to engrave literally means to incise
furrows or grooves on a
copper or steel plate with the use of a graver or burin.
The Technique
The engraver worked with
the lozenge shaped tool called a graver or burin,
rotating the plate as he worked. The lines were incised into the plate
with varying widths
and depths by altering the angle at which the tool met the plate and
the amount
of pressure exerted on the handle.
Differing tones were achieved by changing the
space between the lines, closer together gave a darker area. Cross
hatching also
produced tonal and textural effects as well as providing a more three
dimensional image.
Lithography
Lithography or printing on stone (lithos -
Greek for stone) was invented in 1798 by the Czech, Aloys Senefelder. This is a surface or planographic method of printing and relies
upon the the principle that water and oil do not mix.
A drawing is made on limestone using a greasy crayon or pencil, the
stone is then treated with acid, gum arabic and water so that when ink is applied from a roller it
adheres to the drawing but is
repelled by the remainder of the stone. With a moist stone and regular
in supply an almost unlimited quantity of prints can be produced.
The handling of large slabs of
limestone and the use of a chain hoist to
locate the larger specimens on to the press made this technique somewhat
labour intensive.
A Chromolithograph is
produced by the method above but using many dozens of tint stones
to apply the different inks. Each individual stone has to be properly
aligned so as to register
with the previous ones, and is a technical feat
in its self. This method of printing produces a
wonderful tonal quality and subtle colouring which is very difficult
to reproduce with
modern printing techniques.
Etching
Like engraving, also an intaligo technique. The Etcher prepared the plate by covering
it with a wax based 'ground' and the image was drawn in the wax using an
etching needle,this technique allowed the artist to produce a much more free and expressive image. The edges and underside of
the plate were sealed with varnish for protection and the plate was them immersed
in nitric acid. The acid would bite into the plate where it was exposed by the needle producing an incised
image on the metal.
After the plate was bitten to the satisfaction of
the etcher, it was removed from the acid bath and
washed in hot water to remove all traces acid and the
remaining wax. An ink charged 'dabber' was
then used to work the ink into the incised areas of the plate which
was then wiped to remove any
surface inkA piece of paper was thenlaid on
top of the plate and then passed through a
press allowing the ink to be absorbed by the paper and produce the
printed image.
