The material on which the map was produced can be used as a starting point in the dating process. With the exception of stone (archaeological dating processes must be used here), we can assign, with relative certainty, a general date to the first use of most writing materials.

Clay ca. 4100 - 3800 BCE.
Papyrus ca. 3000 BCE.
Parchment ca. 150 BCE.
Chinese paper, rice or mulberry wood ca. 105 BCE.
Linen paper ca. 900 CE. (in Europe ca. 1150 CE)
Linen wood pulp paper ca. 1800
Wood Pulp paper ca. 1850

With linen paper we have an inbuilt tool to help us with dating the paper. By the beginning of the 13th century paper making in Europe was widespread enough that most of the makers of linen paper wished to be identified through their product, so they imprinted their paper with a water mark. These water marks can often be dated quite accurately, so giving us a date before which the map could not have been produced.

The method used to produce the image, manuscript after ca. 4100 BCE and printed after 700 CE (after 1472 in Europe), can also be used to assist in the dating process.
With hand drawn or “manuscript” maps the writing and drawing tools used to draw it, the form of the letters (paleography), cartographic style of the map and the cartographic content of the map must be examined for a date to be ascertained.

Printed maps are slightly easier to date as the first use of the various printing methods that were used to print maps can be defined.

The woodcut
in Asia (China) the ca. 8th century - 1900
in Europe 1472 - ca.1600

Copper engraving 1477 - 1850 (1950 -60)
Etching ca. 1500
Aquatint ca. 1734
Steel engraving 1820
Lithography ca. 1800 - 1950 - 60
Chromolithography 1836
Color chromolithography ca. 1860

As with manuscript maps the cartographic style and content of the printed map must be taken into account when considering a date.

Defining whether a map is manuscript or printed is also important as the first map printed in Europe is dated to 1472. The question is how do we tell the difference between a manuscript map and a printed map. This is simpler than it may sound. We can quickly separate out maps printed from printing plates as the printing process leaves behind what is termed the plate-mark, a disturbance of the paper fibers where the printing press pushed the paper over the edge of the printing plate. This leaves us with the problem of telling the difference between the manuscript and woodcut or lithograph.
If the map was not printed from a plate we must examine the lines that make up the image. We can with relative certainty ignore any coloring of the map as in both manuscript and printed maps the color was applied by hand. With only a few exceptions, maps were not printed in color until the end of the nineteenth century. The “lines” are those that form the image and are normally black or black-brown. By close examination of these lines we can see a clear difference between the line produced from the ink used for writing and that used for printing. Writing ink is thinner in consistency than that used for printing and therefore it produces a line of varying intensity whereas the ink used for printing was thicker and more consistent in its intensity. Also writing ink tends to penetrate the paper more than printing ink which results in the printing ink appearing to stand out from the paper.
With a woodcut map one further clue that is often quickly apparent is the same characteristic that is seen with text printed from movable type, where the pressure used when printing causes the letters to press through the paper so that one can see and feel the text on the reverse of the paper. This is only apparent with woodcut maps when either the content of the map is sparse or the print pressure is extreme.

With experience it becomes relatively easy to tell the difference between a print and a manuscript map.

To be continued...