While
the light sensitive material is actually effected by the light in
that the silver salts embedded in the emulsion are changed to metallic
silver, leaving the object on top of the sensitive material for an
extended period of time with light falling on it will produce
a print with a 'shadow image'. This can take a very long time, perhaps
days or even weeks.
Although the image will form a a standard photo paper, special POP
or printing out paper can be obtained where the image forms over a
much shorter period of time.
The
image opposite is a photogram of the lower half of an umbrella
with the handle at the bottom, which has been developed only
with exposure to sunlight for 48 hours. After the exposure
the image was fixed and washed in the normal manner to make
the image permanent.
Prints
made like this often have a characteristic pinky-orange colour.
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I
have made photograms using this method with standard photographic
paper.
1 Thomas Barrow used this method with 20x24
Grade 5 Kodabromide paper in the New Mexico sunlight using exposures
of 30-60 min's.
