646
1760s by J.B. Le Prince (1734–1784). With this print-
making process a full scale of tone is obtained by etching
a multitude of extremely small pockmarks in a random
manner on the printing plate. This is achieved by sprin-
kling the metal plate with resin particles in a specially
designed dustbox. When the plate is heated the particles
adhere to it and create minute areas of grain. The plate is
then placed into an acid bath that eats into the exposed
areas of metal. The design on the plate is developed and
the gradations of tone are achieved by repeated bitings
of the plate. In the fi rst rebiting, all the areas intended
to be in the lightest tone, are “stopped out” or covered
with an acid resisting varnish, and the plate is again
immersed in the acid bath. The process is repeated until
a full scale of tone is obtained, the darkest tone being
those that are etched the longest and deepest.
Niepce de Saint-Victor had documented the use of
the aquatint grain in his Traité Pratique de Gravure
Héliographique (Paris 1856, 44). The idea was also
exploited by Paul Pretsch and Karl Klic, in their work on
photogalvanography and photogravure, among others.
Among the most successful héliograveurs we must
mention the work of Charles Nègre (1820–1880) who
was considered by his contemporaries to be the fi rst
to obtain truly remarkable results with his version of
the asphalt process. He used the process to produce
intaglio steel plates for a monograph on Chartres’ Ca-
thedral, with which he won the highest rewards offered
at the Exposition Universelle of 1855. Although Nègre
used “offi cially” the bitumen process with an aquatint
grain, he probably utilized dichromated gelatin as in
the photogravure process for his later work. Nègre
always worked alone and never accepted students, so
his techniques were never fully understood. Nègre also
experimented along the lines of Pretsch’s photogalva-
nography process.
According to Louis-Philippe Clerc, Edouard Baldus
(1813–1889), Garnier & Salmon and Charles Nègre used
a variant of the aquatint technique where the printing
plate was etched in multiple stages, a process used in
some Paris printing plants up until the 1920s.
Luis Nadeau
See also: Goupil & Cie; Klič, Karel Vaclav; and
Photogravure.
Further Reading
Bacon, S.W., “The bitumen process, and the chance of its surviv-
ing its modern rivals.” Penrose Annual, Vol. 1, 1896, 49–50.
Bonnet, Manuel d’héliogravure, Paris: Gauthier-Villars, 1890.
Clerc, Louis-Philippe, La Technique des Reproductions Photo-
mécaniques. Paris: Bouzard-Calmels, 1947.
Geymet, Traité pratique de gravure héliographique, Paris:
Gauthier-Villars, 1885.
Gottlieb, S., Praktische Anleitung zur Ausübung der Helio-
gravüre. Halle: 1905.
Gravier, Ch., “Photographic processes used in book illustrations.”
Penrose Annual, vol. 7, 1901, 109–110.
Marignier, Jean-Louis, Niépce, l’invention de la photographie.
Paris: Editions Belin. 1999.
Martelle-Thiele, Héliogravure au grain, trichromie, rotogravure,
impression, Paris: Sfelt. 1934
Nègre, Charles, De la gravure héliographique: Son utilité, son
origine, son application, Nice: Gauthier & Cie, 1867.
Niepce de Saint-Victor, Abel, Photographic Researches. Photog-
raphy Upon Glass. Heliochromy. Heliographic Engraving.
Various Notes and Processes, by M. Niepce de Saint-Victor.
Followed by Considerations by M. E. Chevreul,... with a
Biographical Preface and Notes, by M. Ernest Lacan. Paris:
A. Gaudin. 1855.
Ribette, A., Traité pratique d’héliogravure en creux sur zinc,
au bitume de Judée, accompagné de notions et de quelques
procédés lithographiques, zincographiques pour la reproduc-
tion: 1e. des cartes topographiques ou géographiques et plans
divers à toutes les échelles; 2e. de tous les genres de dessins
à la plume imitant parfaitement la gravure au burin. Paris,
Charles Mendel, 1903.
Roger-Laurent, Heliogravure, Bruxelles, 1876.
Schiltz, Manuel pratique d’héliogravure en taille-douce. Paris:
Gauthier-Villars, 1899.
Tissandier, Gaston, L’Héliogravure, son histoire et ses procé-
dés, ses applications à l’imprimerie et à la librairie. Paris:
Imprimerie Pillet Fils aîné, 1874.
Waterhouse, J.J., “Nicéphore Niepce’s early photographic work
with bitumen.” Penrose Annual, vol. 19, 1913, 145–146.HELMHOLTZ, HERMANN LUDWIG
FERDINAND VON (1821–1894)
German scientistHermann von Helmholtz was born on 31 August in
Potsdam, Germany. His father, Ferdinand Julius Helm-
holtz, had served in the Prussian army fi ghting against
Napoleon then, having a good university education, he
taught philology and philosophy at Potsdam Gymna-
sium. It was a poorly paid job and Hermann, the eldest
of four children, was brought up in fi nancially diffi cult
circumstances. Ferdinand was artistic and his infl uence
meant that Hermann grew up having a passion for music
and painting. Hermann’s mother Caroline Helmholtz,
the daughter of an artillery offi cer, was a calm person
who also strongly infl uenced his character.
Hermann attended Potsdam Gymnasium where his
father taught. He was interested in physics and would
have liked to have studied that subject at university but
the family’s fi nancial position meant that was only pos-
sible with a scholarship. Hermann’s father persuaded
him to study medicine which was supported with gov-
ernment scholarships. In 1838 Helmholtz entered the
Royal Friedrich-Wilhelm Institute of Medicine and
Surgery in Berlin. The scholarship he received had
strings attached, however, committing him to ten years
as a doctor in the Prussian army after graduating. During
the medical course he also attended courses in chemis-