6. Amand Durand, Dulos.

In 1867, Amand Durand presented to the Société Française de Photographie "various specimens of heliography on steel and copper for typography and copper-plate engraving". This engraver who claims to use Nicéphore Niépce's early method declares that he prefers "this technique to those based on using bichromate mixes, because the proofs obtained with them, unlike those obtained by using bitumen of Judea, are unable to resist deep acid etching". Amand Durand's proofs are nevertheless retouched using ordinary engraving techniques.

In 1883, A. Poitevin quoted the brochure Essai sur les Gravures Chimiques en Relief written by M. Motteroz. From it he took a passage that describes a technique used by a Mr. Dulos, worthy of being mentioned as an example of the complex handling that images produced by asphalt could entail.





These images were obtained on a copper plate, as is the case for all asphalt-produced images (a). Then, using a battery, Dulos had iron electrochemically deposited on it. The iron deposited only where there was naked copper. It did not deposit on the asphalt (b). He then took off the asphalt by dissolving it with benzene (c). Afterwards, he provoked an electrochernical deposit of silver. The silver fixed on the copper and not on the iron (d). In fact the silver replaced the asphalt. Dulos then eliminated the iron by using an acid (e) and then poured mercury on the plate. The mercury formed an amalgam with the silver. This amalgam formed a relief (g) and, depending on whether he intended to reproduce a positive or a negative, Dulos obtained either an intaglio engraving or a typographic plate.


7. Gillot's Technique

In 1850, Firmin Gillot (1820-1872), the French lithographer, created panicography, a process for obtaining a matrix for doing typography from line drawings made on lithographic stone.



In 1872, his son adapted the process to the handling of photographic images (a) produced either by using asphalt or by use of bichromate gelatine on a zinc reserve base.
The technique of acid engraving to which he gave the name of gillotage was very refined and called for a succession of acid and ink applications. Its purpose was to cover the edges of each engraved line with ink so as to protect them from being broadened by further acid bites (b, c, d, and e).
The technique could only be used to reproduce drawings or line engravings. To use the technique for other types of illustration, Charles Cillot developed several methods for obtaining a photographic image with a grid or grainy effect that was applied and then reproduced on an asphalt varnish.

The technique of gillotage was later used to engrave metal. It was used to make photographic prints, was very successful and was sometimes called direct photoengraving