HF The History of Photography 600pág

188 The early years of photography
In the calotype process, the light-sensitive substances were coated on the surface
of the paper, resulting in negatives which were too contrasty and lacking in halftones.
Blanquart-Evrard, on the other hand, floated his paper on two successive baths
of iodide of potassium and nitrate of silver (reversing the procedure of Talbot). By
this means the paper was thoroughly impregnated and consequently gave a much
greater gradation of tone and detail. The sensitized paper could be kept for several
months, but before use it had to be damped with an acid solution of nitrate of silver
and exposed-backed with moist paper-between two thin glass plates. Gallic acid
was only used for developing, not in sensitizing as in the calotype, and exposures
were reduced to about one-quarter of that necessary for a calotype or a daguerreotype.
A drawback of Blanquart-Evrard's method was that the final preparation requiring
to be carried out immediately before exposure, necessitated the transportation of a
dark-tent and chemicals, and this offset to a certain degree the advantages gained.
Three years later he therefore suggested a further modification, namely, a dry negative
paper prepared with whey and white of egg as a support for the silver salts; this
was slower but could be prepared beforehand, thus 'freeing the operator from the
difficult preparations which he has to make at the places of exposure'.5
The publication of Blanquart-Evrard's wet process 'marked the beginning of a
new era for photography on paper' .6 Baron Gros, as already mentioned in chapter
IO, foresaw that the daguerreotype had almost run its course, and that its rival on
paper was destined to supersede it.7
The enthusiasm with which Blanquart-Evrard's process was greeted gave him the
idea of exploiting it commercially for the large-scale printing of positives from
amateurs' negatives and for book illustration, just as Talbot had done at the Reading
establishment, and in July 1851 he opened such a printing firm at the estate of his
his friend and partner Hippolyte Fockedey, on the outskirts of Lille. It was on a much
larger scale than the Reading establishment had been. The work was carried out by
forty girls who divided their time between photography and agriculture, according
to the amount of printing to be done. In the organization of the various departments
the Lille establishment can be counted as the forerunner of similar modern firms.
Everything was scientifically planned in rooms in which the temperature was maintained
at 70° F. The printing-paper having meanwhile been further modified contained
gelatine, and iodide and bromide of potassium. After fuming over dilute
hydrochloric acid, it was sensitized in the nitrate of silver bath. Immediately it was
dry the paper was put in a printing-frame which ran on wheels upon a pair of rails
up to a shuttered window in a darkroom, the shutter being raised for the requisite
number of seconds. The printing frame was then taken to the developing room
where a number of girls at a row of benches developed the prints in large dishes,
several at a time, in a saturated solution of gallic acid for about 20 minutes. Developing
positive prints like negatives shortened the exposure to a few seconds and allowed
them to be turned out on a mass production scale. In this procedure, originally suggested
by Talbot for calotype prints but soon abandoned, Blanquart-Evrard was
very much ahead of his time, for it only came into general practice with gelatine
papers. Printing with albumen paper was a very slow printing-out method, as will
be seen in chapter 29. Blanquart-Evrard claimed in 1851 that as many as 200 to 300
copies could be printed from one negative per day, and hence they could be sold at
5 to 15 centimes according to size.7 THOMAS SUTTON, who was associated with
Blanquart-Evrard from 1855 to 1857, mentions8 that he saw 250 prints made from
one of his own negatives in less than 2 hours, and notes that in general the exposure