DAGUERREOTYPE PROCESS. By this process a direct positive is obtained upon a silvered metal plate. It was first published by M. Daguerre, in Paris, in January, 1839.
The picture is produced by means of the impalpable filmes of iodine, bromine, and mercury, acting on a silvered plate which has been polished to the utmost, The photo-chemical reactions con sequently occur in an inappreciably small quantity of material, which is spread on the photographic tablet with a uniformity not to be obtained by any other means. Hence it follows that a fine daguerreotype exhibits microscopic perfection of detail, and perfect gradation of shades. Other processes, when compared with this, are coarse and imperfect in the results, and of all known methods of representing a natural object, the Daguerreotype process is the most perfect and scientific.
In a fine daguerreotype, the utmost delicacy of line is combined with perfect gradation of shade ; the details of the deepest shadows are as legible as those in full light ; and the most elaborate finish is blended with exquisite softness of effect. In tone, nothing can be more beautiful than the varied hues of gold and purple which the image presents when viewed in different positions in a strong light.
Unfortunately, however, the very circumstance which gives such perfection to the result, viz., the polish of the plate, brings with it certain objections in an artistic point of view ; and these objections are considered by many to be so serious that they are willing to rest content with an inferior photograph upon a different tablet. Hence the present popularity of the glass and paper processes. But the accomplished photographer, who sees in every process its own peculiar merits, will hardly rest satisfied with a sketchy production, when called on to exhibit the utmost perfection of his art. We would therefore earnestly call the attention of our readers to this elegant and beautiful process, at present so undeservedly cast into the shade by others of less merit.
The manipulation of the daguerreotype process is extremely easy and certain. It involves the following five operations, viz. :
lst.—To clean and polish the plate.
2nd.—To render it sensitive.
3rd.—To expose it in the camera, 4th.—To develop the image, 5th.—To fix the image.
The finished picture is placed in a frame or passe-partout, behind a glass. The image is pePmanent, and cannot be rubbed out by the finger ; nothing but a chemical solvent will obliterate it.
The silvered plates generally employed in this process are manu factured in France, England, and America. The English plates are the best—but they are dear. The amateur had better make his first experiments on the American plates of Scovill and Co., or on the cheaper kinds of French plates, of which there are many varieties. He must choose them as free from scratches and specks as possible, as these defects cannot be remedied. The plates are made by laying a thin sheet of silver foil upon a copper plate, and then passing it between rollers, by which means the two metals are made to adhere perfectly. The silver should contain no alloy. When the same plate has been used several times, the silver wears off, and the plate should then be re-silvered by the electrotype process ; but all scratches and specks are faithfully copied, so that this process does not afford a remedy for these defects. A scratched plate is useless, except for experiments. The plates may be cut to any shape by a strong pair of scissors.
In what follows, the plate is assumed to be the quarter size.
Operation.—To Clean and Polith the Plate.—If necessary, eat a little bit off each corner, and bend the edges in a plate bender.
To clean the plate, procure some Canton flannel, and a box of prepared rotten stone with a muslin strainer. In a pint bottle mix one part nitric acid and twenty parts clistilled water.
If the plate has been used before, and has been submitte,d to the gilding solution, the image must be removed by a liquid sold under the name of " Gilding Dissolvent ;" the directions for using which will be found on the label of the bottle.