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string(19) "photogenic_drawings"
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string(3) "PHD"
["_name"]=>
string(19) "Photogenic drawings"
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["_popular_start_date"]=>
string(4) "1835"
["_popular_end_date"]=>
string(4) "1845"
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string(11) "photographs"
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string(19) "photographs by form"
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string(9) "negatives"
["_aat_level_4"]=>
string(20) "negatives by process"
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string(56) "1_early_photography_-_processes_-_photogenic_drawing.htm"
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["_private_notes"]=>
string(2044) "Photogenic Drawing
The first name given by William Henry Fox Talbot to the photographic process that he announced in January 1839. "Superfine writing paper" was dipped in a weak bath of common salt and after blotting was brushed with a solution of silver nitrate. The light-sensitive silver chloride formed in the fibers of the paper was not highly sensitive to light and after the photogenic drawing paper was prepared and dried it required exposure in direct sunlight from ten minutes to an hour depending on what object (leaves or lace) or image (waxed engraving) had been placed over it. Talbot fixed the resulting image, which had printed-out during exposure, in a moderately strong solution of potassium-iodide or a strong solution of common salt. We now consider these prints to be "stabilized" rather than fixed. Treatment with potassium iodide created a very pale primrose yellow hue in the highlights while common salt produced a pale lilac tint.
Photogenic drawing paper intended for camera exposures had to be more sensitive, and thus Talbot coated the paper as many times as he could, alternating between common salt and silver nitrate, before the paper would spontaneously blacken on its own. With an f/11 lens, these exposures ranged between on and two hours. The negative camera images were formed by printing-out and not by development, which was a later discovery (see calotype). As early as February, 1835, Talbot had printed photogenic drawing negatives as positives (which he then called "transfers"). In order to successfully print the weak images of camera negatives, Talbot devised a negative paper in February/March 1839 that was based on silver bromide, and which was more responsive to light than even the multiply coated silver chloride paper. These new negatives of considerably higher contrast produced better positives on the original photogenic drawing paper. When the calotype process became the standard way of making camera exposures, Talbot printed these negatives on photogenic drawing paper, as well."
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