THE next person to take up the subject of sun-pictures, and carry it forward from the point where Wedgwood and Davy had left it was a Frenchman named Niepce. Indeed, although his name was for years eclipsed by another, there is no doubt that to Niepce belongs the largest share of the honour due for the invention of photography, or, as he called it, heliography (from hedos, the sun).
Joseph Nicephore Niepce was born at Chalon-sur-Saone in 1765. His father, Claude Niepce, was a ” conceiller de roi,” and in easy circumstances, his mother the daughter of a distinguished lawyer named Barrault. As a youth Niepce was of a dreamy and poetical turn, and did not show any particular inclination to choose a profession. In 1792, however, he entered an infantry regiment as sub-lieutenant, and in the following year saw active service in Sardinia and Italy. Shortly afterward he was obliged to resign his commission in consequence of ill-health and failing sight.
In 1794 he was appointed a member of the administration of the district of Nice. Continuing to hold this position until 1801, he then relinquished it to follow what had always been his chief bent, study and research. Returning to his native place, he there devoted himself, along with his elder brother, to scientific investigation. Several mechanical inventions which he made received from M. Carnot, the Minister of Finance, the most flattering encouragement ; while his researches in reference to the colouring matter of pastel attracted the attention of the commission charged with the examination of substances suitable for dyeing.
All these labours, however, are now forgotten in the invention with which his name is chiefly associated, which absorbed the last twenty years of his life, and cost him the fortune that he had inherited from his father.
Lithography, which was then but newly invented, and was consequently much talked about, greatly interested Niepce, and he devoted much time in the endeavour to improve the process. At first he replaced the stone by a plate of tin ; “then,” says one of his biographers, “in 1813 he was seized with the idea of finding a substitute for the lithographic chalk with which the designs were drawn, and the almost fantastic idea took possession of his mind that they might be done by light itself.” From that moment he could think of nothing elsecould work at nothing else.
Niepce was acquainted of course with the quality possessed by chloride of silver of becoming dark when exposed to the light. From this fact he was led to infer the possibility of reproducing designs and engravings by rendering the paper transparent, and applying the design or picture to a surface to which had been given a coating of silver salt. The dark parts, preventing the passage of light, would leave the parts corresponding to the salt white. Thus a ” negative ” would be produced, which, by a second operation, would exactly reproduce the original.
The idea was simple enough, and seemed feasible. In practice, however, the thing could not be done. There was no difficulty about the production of the negative; but as soon as it was exposed to the light the white portion became dark, and the design was quite obliterated.
In short, he had repeated the experiment of Wedgwood and Davy, and found himself confronted with the same difficulty which stopped them. The question that Niepce now had to solve was, how could the sun, after it had produced a picture, be prevented from destroying it. This second effort was a more successful one. He discovered-it is not known howthat asphalt, or bitumen of Judea, a substance which is found in the Dead Sea, the Caspian, and other places, possesses the quality of becoming soluble in ethereal oils, such as oil of turpentine, oil of lavender, petroleum, ether, etc. This property Niepce made use of in a most ingenious way. He poured a solution of bitumen upon a metal plate, and allowed it to cover the surface, which soon dried in the form of a brown film. Taking a plate thus coated, he placed it where the image of the camera obscura falls, and then exposed it to the light, the result being that the asphalt remained soluble on the dark parts, that is, the shadows, of the image, while the light parts became insoluble. The eye does not perceive these changes ; but if oil of lavender be poured over the exposed film of asphalt it dissolves those parts that have not been changed, leaving behind only those that have been affected by the light, that is, the parts which have been rendered insoluble. Thus, after several hours’ exposure in the camera, and subsequent treatment with essential oils, Niepce succeeded in obtaining a picturea picture traced upon the metal plate in lines of asphalt.
He now went a step further, and made the attempt to utilise his discovery as a substitute for engraving on copper. To produce a copper-plate print, a smooth plate of copper is engraved with a tool for that purpose called a burin, the lines that are to appear black in the picture being cut into the plate. In order to obtain impressions, ink is rubbed into these lines, then a sheet of paper is laid upon the plate and placed under a roller-press, which causes the ink to be transferred to the paper, thus producing a “print” of the inked lines.
Niepce’s idea was to produce these lines in the copper by the action of light ; and to effect this object he covered the copper-plate with bitumen, and exposed it to the light beneath a drawing on paper. The black lines of the drawing of course prevented the light from reaching the bitumen on the plate. Accordingly in those parts not affected by the light the bitumen remained soluble, while in those parts where the light had penetrated the white paper, it became insoluble. When, therefore, oil of lavender was subsequently poured over the plate the portion of the bitumen which had been rendered insoluble adhered to the copper, whilst the other parts were dissolved and washed away. Thus on the film of asphalt the original drawing appeared as if engraved.
A corrosive acid was now poured upon the plate, and acted on the metal when not protected by the asphalt, eating into it, in fact. Thus an incised drawing was produced by the action of the acid, and, after cleaning, could be printed from in the same manner as a copper-plate engraved by hand.
Copper-plate prints of this description were found amongst Niepce’s papers after his death. These, which he called ” heliographs,” he is known to have shown to his friends as far back as 1826.
This method in an improved form is in use today, and is especially useful in the printing of bank notes, where it is necessary to have a number of plates all absolutely alike, so that one note may be an exact facsimile of another and be easily distinguishable from counterfeits. Some of the notes of the German States, notably Prussia, are thus produced.
The original inventor of the method, however was not able to attain that perfection in his impressions which subsequent experimenters succeeded in achieving. Not being satisfied there-with himself, Niepce relinquished his labours in this direction and devoted his attention to other lines of research in regard to fixing the images of the camera obscura. But it was unquestionably these discoveries that led in the end to one of the most useful applications of photography, the combination of photography with copper-plate printing above described.
In his description of the method he employed Niepce recommends that the asphalt or bitumen be reduced to a powder and the oil of lavender dropped upon it in a wine-glass, and then gently heated. A metal plate, highly polished, was covered with this solution, and when dry it was ready for employment in the camera. For his engravings Niepce preferred plate of silvered copper.
In 1827 Niepce went to England on a visit to his brother Claude, who was living at Kew, where he had settled many years previously with the object, apparently, of pushing some ingenious inventions, the joint production of himself and Nicephore. Here he was introduced to Dr. Bauer, the Secretary of the Royal Society, and through him endeavoured to bring his discovery before that body; but as Niepce refused to make known his process his communication was not accepted.
It is to be presumed that the paper which he offered to submit to the Royal Society was subsequently lost or destroyed, as no account of his method was ever published by Niepce; and the only description thereof that we have is one contained in an agreement made between him and his collaborator, Daguerre, in December, 1829. In that document he says: “The discovery which I have made, and to which I give the name of heliography, consists in producing spontaneously, by the action of light, with gradations of tints from black to white, the images received by the camera obscura. Light acts chemically upon bodies. It is absorbed ; it combines with them, and communicates to them new properties. Thus it augments the natural consistency of some bodies; it solidifies them even, and renders them more or less insoluble, according to the duration or intensity of its action. The substance which has succeeded best with me is asphalt, dissolved in oil of lavender. A tablet of plated silver is to be highly polished, on which a thin coating of the varnish is to be applied with a light roll of soft skin. The plate, when dry, may be immediately submitted to the action of light in the focus of the camera. But even after having been thus exposed a length of time sufficient for receiving the impressions of external objects, nothing is apparent to show that these impressions exist. The forms of the future picture remain still invisible. The next operation then is to disengage the shrouded imagery, and this is accomplished by a solvent, consisting of one part by volume of essential oil of lavender, and ten of oil of white petroleum. Into this liquid the exposed tablet is plunged, and the operator observing it by reflected light, begins to perceive the images of the objects to which it had been exposed, gradually unfolding their forms. The plate is then lifted out, allowed to drain, and well washed with water.”
Niepce goes on to say : ” It were, however, to be desired that, by blackening the metal plate, we could obtain all the gradations of tone from black to white. The substance which I now employ for this purpose is iodine, which possesses the property of evaporating at the ordinary temperature.”