HF The History of Photography 600pág

Photomechanical printing processes 543
same result, and by various means he succeeded for many years in controlling in
England all methods of making pictures by light, except the daguerreotype. He now
aimed to control all photo-engraving processes depending on the light-sensitivity of
bichromate of potash and organic substances, and this in spite of Mungo Ponton's
and Becquerel's fundamental observations, without which he ·could not himself have
succeeded. Jabez Hogg complained20 that he was prevented from illustrating his
book on the microscope with photo-engravings (in this case, photographs transferred
on to the wood block) 'by the existence of a patent which presented obstacles too
great to be surmounted at that time'.
While Talbot's interference proved no more than a nuisance, Pretsch's one-time
manager of the firm, CAMPBELL DUNCAN DALLAS, caused more serious trouble. The
only person with access to the secrets of Photogalvanography, he was only prevented
from patenting 'certain chemical improvements' in June 1856 by being unable to
furnish the detailed specification.
Dallastype. After Pretsch's patent had lapsed in November 1860 through lack of
money to pay the renewal fee, Dallas took up the process, and with some modifications
reintroduced it in 1863 as 'Dallastype'. He made no attempt to patent the
method nor did he publish it, according to his own statement because he wanted to
reap the fruits of his labours, 21 but according to J. M. Eder22 because he had fraudulently
appropriated Pretsch's invention. However that may be, the Dallastype
specimen presented with The Photographic News of 1 January 1864 does surpass the
results of Pretsch inasmuch as it was untouched by the engraver. We would not,
however, go so far as did the editor in claiming that this engraving was 'the very best
result of the kind ever produced' (up to 1864), for in France, less hampered by patent
laws than England, great strides had been made in photo-engraving.
In 1869 Dallas formed a company called the Dallastype W arks which accepted
customers' orders for electro- and stereotype copies of woodcuts, pen and ink drawings,
copper or steel-plate prints, and lithographs in line or chalk, but not half-tone
photographs. These were apparently too difficult or too costly. In a pamphlet Dallas
stated that over 25,000 copies could be machined off one type-metal block, and if
transferred to stone the Dallastype would be found more efficient and more economical
than other methods of photolithography. On I March 1875 Dallas issued a
four-page 'Proposal for Divulging the Dallastype Process of Photographic Engraving
to 500 subscribers or more at £20 each', declaring his intention to retire from
business. The outcome is not known.
Heliogravure. Foremost among the experimenters in France was NIEPCE DE SAINT- Pl 319
VICTOR, Commandant of the Louvre, who since 1853 had been trying to improve
the bitumen process of his cousin Nicephore. Eventually, in October 1855, a modified
bitumen method on steel plates, worked out in collaboration with the engraver
LEMAITRE, was perfected enough for the production of half-tone pictures. The two
heliogravure portraits of Niepce made by A. Riffaut, which serve as frontispieces to
his books Recherches photographiques and Traite pratique de gravure heliographique, are
proof of the excellent quality that could be achieved in I 8 5 5 and 18 56 respectively,
'with some assistance from an engraver' as Niepce admitted. Even before that time,
on 7 October 18 54 a perfect half-tone engraving of the Bibliotheque du Louvre by
Mme P. Riffaut had been published in La Lumiere, and what is particularly remarkable,
it had been printed alongside the text of the journal on the same paper.
In 18 54 E. BALDUS and CHARLES NEGRE, both painters as well as photographers,
obtained good results with intaglio and relief engraving on a bitumen coating on
steel. Whereas Baldus was chiefly interested in reproducing line engravings, Negre