is a Photochrome?
First of all, is it spelled “Photochrome” or “Photochrom?”
The process was initially
Switzerland and was spelled without an “e”, so the correct original spelling was
actually “Photochrom.” When the process was introduced in
America, the “e” was added to aid
A Photochrom is a colour photographic lithograph, produced from a black-and-white
negative. The final prints were created using different colour impressions
from multiple lithographic stones. The stones used by the Detroit
Photographic Company were imported from
Bavaria and coated with a special Syrian
“asphaltum” substance that would be chemically sensitised to light, put in
contact with a photographic negative, exposed to the sun for up to several
hours, then “developed” in oils of turpentine.
The areas of the very thin asphalt gel most exposed to light would harden,
becoming insoluble; the less exposed residue would be washed away. Tonal
values of the remaining positive image could be manipulated by varying the
chemistry and development times. Technicians could do the equivalent of
photographic burning and dodging by retouching the brush and polishing with
fine pumice powder. The final steps in preparing the stone were an acid etch
to bond the remaining image with its very fine grain, and a glycerine bath.
A separate stone would be made for each colour to be used. A minimum of four
stones and as many as fourteen stones might be used for a given image. A
transparent ink would be applied to the stone, then transferred to
high-quality paper whose texture resembled the smooth photographic printing
paper of the day.
The final steps was a varnish which gave each print added depth and
richness. Because the process involved a number of crafts people and because
the stones had to be re-ground occasionally, substantial variations may be
noted between different editions of the same image over the years.
When viewing the pictures on your computer, please bear in mind that the low
resolution that the internet demands for fast downloading cannot do justice
to the quality of these superb prints.
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