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M. Duloz is nameless no more! He is Pierre Edelestand15 Stanislas Dulos! – a worthy
name for a legendary engraver.

The misspelling, Duloz instead of Dulos, kept this information hidden. Searches
with the Dulos spelling then led to the complete text of his 1860 patent application.
It appears in a volume digitized on Google Books.13 The patent was filed on February
18, 1860 and granted on August 30, 1860.14

The patent describes a process based on the fact that mercury and certain
amalgams of mercury will adhere to silver plates only where the silver is exposed and
not where the plate is covered by certain substances such as varnish or a lithographic
pencil line. In addition the mercury amalgam will form a raised surface on the parts
where it adheres, and will react with the silver to form an insoluble compound. Dulos
recognized these qualities could be used to produce a recess–engraved plate (intaglio)
by first drawing on a flat silver or silver–coated copper plate and then covering the
plate with a mercury amalgam that will adhere everywhere but where the drawn
lines are. When hardened, the mercury will produce a plate with recessed lines
corresponding to the drawn lines, which can then be used as a mould to produce an
intaglio plate. The same process can also be used to produce a surface printing plate
(typographic) by treating the plate so that only the drawn lines have the silver base
exposed. By washing the plate with a mercury amalgam, the mercury will adhere
only where the drawn lines are exposed, producing a plate with raised lines suitable
for making a mould for a typographic plate. Finally, he recognized that the same
process can be used to make intaglio or typographic plates of drawings and prints.
Passer was confused about this procedure and mistakenly thought that it involved
creation of a typographic plate directly from an intaglio one; what was said is simply
that both types of printing plates can be made starting with a flat (silver–coated)
copper plate, used traditionally for intaglio.

Apparently he used this process to prepare the typographic plates for printing the
Duloz stamps from the designs provided to him.

Dulos had also applied for the same patent in France on December 30, 1859. It was
described as “Un nouveau procédé de gravure des planches d’impression en creux
et en relief” (“a new process for engraving printing plates in hollow and relief”).15 In
that work he is referred to simply as “sieur Dulos, à Paris.”

But the correct spelling leads us to much more than just patents. In 2001, Klaus
Hentschel, a renowned historian of science and technology, and his wife published a
long article about Dulos! The article is entitled “An Engraver in Nineteenth Century
Paris: The Career of Pierre Dulos.”16 In 2005 Hentschel published a second article on
Dulos in German.17

Hentschel’s article tells us much about Dulos’ life. Pierre Dulos, or more fully
Pierre Edelestand Stanislas Dulos, was born on June 1, 1820, in Dax, a small town in
the Landes department in the far southwest corner of France.18 Between 1835 and
1838 Dulos studied industrial arts at the local École Nationale des Arts et Métiers in
Angers.19 On January 26,1860, he married Lucie Legrand with whom he would have
two children.20 By late 1850 or 1851 he was in Paris working as an engraver for the
Parisian Académie des Sciences and between 1852 and 1874 he executed a great
number of copper engravings of technical subjects, both for the Académie and the
publisher Imprimerie Loiguon & Cie.21 His works were signed simply “Dulos sc” for
“Dulos sculpsit,” i.e., engraved by Dulos, a name rather rare in France, allowing him
to dispense with his initials, which would have been the common practice.22 Many
of his engraved plates appeared in technical journals such as the Annales de Chimie
et de Physique.23

Collectors Club Philatelist Vol. 94 No. 2 March–April 2015 101