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Cliché verre A contemporary account of the discovery of Cliché verre by William Havell and / or Frederick James Havell and James Tibbitts Willmore. Note the mispelling of Willmore in the original text.
"Photogenic Drawings", Foreign Quarterly Review (London) 23:45 (April 1839): 213–18.
We must leave this question and now proceed to analyze the claims of two of our countrymen, Messrs. Havell and Wellmore [sic], who are said to have introduced an important addition to the process pursued by Mr. Talbot, a full description of which is contained in a letter to the editor of the Literary Gazette. The first attempt of this gentleman was directed towards an etching, by Rembrandt, of an old man reading, and the result was a reversed fac-simile;—a negro face surmounted by locks of silver; the disappointed artist discovered that a second transfer entirely destroyed the spirit of the picture. To remedy this evil he had recourse to a new process, by which this defect was indeed removed, but the great merit of the art, namely, its self-acting power, was lost. A thin plate of glass was laid on the subject to be copied, upon which the high lights were painted with a mixture of white lead and copal varnish, the proportion of varnish being increased for the darker shading of the picture. The next day Mr. Havell removed the white ground with the point of a penknife, to represent the dark etched lines of the original, and a sheet of prepared paper having been placed behind the glass and thus exposed to the light, a tolerable impression was produced; the half tints had however absorbed too much of the violet ray, an imperfection which was remedied by painting the parts over with black on the other side of the glass; if allowed to remain too long exposed to the sun’s rays the middle tints became too dark and destroyed the effect of the sketch; about ten minutes in a powerful sun was considered sufficient. Another method employed by Mr. Havell was to spread a ground composed of white lead, sugar of lead, and copal varnish, over a plate of glass, and having transferred a pencil drawing in the usual manner, to work it out with the etching point till it bore the appearance of a spirited ink drawing, or in the hands of an engraver a highly finished engraving. The above process Mr. Havell made public under the impression that it had been hitherto overlooked, but Mr. Talbot hearing that he was about to apply for a patent laid claim to the improvement as his own, and not only pointed out some parts of his former memorial where it was distinctly mentioned, but also produced several drawings made precisely in the manner described; he has also laid before the Royal Society a new method of preparing the sensitive paper, which consists in immersing it in a solution of nitrate of silver, and, afterwards washing it with bromite of potassium the nitrate of silver is again applied, the preparation being dried by the fire between each operation; the paper thus treated is extremely sensitive, changing with the feeblest daylight, first to a bluish green, then to olive green, and finally to black.