SearchAbout This SiteTreatment ForumVideo clipsGalleryScienceLibraryTechnology

Towler, John. The Silver Sunbeam. Joseph H. Ladd, New York: 1864. Electronic edition prepared from facsimile edition of Morgan and Morgan, Inc., Hastings-on-Hudson, New York. Second printing, Feb. 1974. ISBN 871000-005-9

Chapter XXXIX.

A PHOTOGRAPH on a silver or silvered plate is superior in definition and beauty to all other photographs taken on other materials. It has, however, its disadvantages; amongst these may be reckoned the lateral inversion of the picture, the inability of regarding the image at all angles of reflection, and of producing reproductions of the original by some quick printing process.

The Daguerreotype process is divided into six different operations.

First Operation, or the Cleaning and Polishing of the Shivered Plates.

Copper plates can be purchased already silvered with a pure frosted silver surface, of the proper size and ready for the polishing. In the first place, with a pair of shears, clip off the four corners of the plate, about a quarter of an inch from the apex of each angle; next with the machine for this purpose make a ledge all round the plate of one tenth of an inch in width from the silver side toward the copper side, so as to form a groove such as the tinman makes when grooving two edges of tin together. The plate is then fixed on a patent plate-holder, which in its turn is next screwed tight in the plate-vice. In this condition the silvered surface can easily be cleaned. This is effected by means of rotten stone, alcohol and Canton flannel, which are used in the same manner exactly as in the cleaning of glass plates. As soon as the plate is perfectly smooth and free from scratches, it is polished with what is called the buff, which consists of a piece of wood, about fifteen or eighteen inches long, four or five wide, and about three quarters of an inch thick; this piece is slightly curved longitudinally like the rocker of a chair, though to a less extent. It is well padded on the convex surface and finally covered with chamois leather. On the surface scatter a small quantity of jeweler's rouge, (sesquioxide of iron,) and then holding the buff by either end in the right and left hand move it backward and forward over the smooth silver plate, first in one direction and then at right angles to it, until the surface has a very uniform rich polish, devoid of lines. The plate is then ready for being sensitized. The buffing is more easily and uniformly executed on what is denominated the buffing-wheel.

Second Operation, or the Sensitizing of the Silver Plate.

For this purpose two coating-boxes are required, one containing the vapor of iodine, and the other that of bromine. They are so arranged as to allow the introduction of the polished plate without any loss of vapor. These boxes must be kept at a warm temperature so as to evolve the vapors from the materials; in winter artificial heat is used. One coating-box contains at the bottom first a piece of Canton flannel, and then about half an ounce or more of iodine in crystals; the other contains a mixture of hydrated lime and bromine, well pulverized and mixed. The operation is performed in the dark-room near the orange-colored pane of glass. The polished plate is first inserted in the holder of the iodine coating-box, and the lid is then closed. The surface, if examined closely, assumes various shades of color, beginning with light yellow, then deep yellow, reddish, copper-red, violet, blue, and green. As soon as the plate passes from the yellow to the red, it is placed over the bromine vapor, and kept there until the reddish color changes into a violet or steel color; it is then put back again over the iodine for one third of the time of the first exposure. By this means the film receives a very high degree of sensibility. The times of these three exposures, as soon as determined by practice, are counted in seconds. A more sensitive film may be obtained by iodizing simply to the light yellow, by bromizing to the dark yellow, and then again over the iodine for one third of the first exposure. This film, however, is very thin and not suitable for portraits, although well adapted for views. The plate is now ready for the

Third Operation, or the Exposure to Light.

It has been observed that the sensitized plates are more sensitive to the actinic impression if not exposed for a quarter of an hour after sensitization; in general, however, the plate is transferred directly from this operation to the plate-holder of the camera, and exposed right away. The time of exposure is very short; it is naturally various, as in all other and similar cases depending upon the brilliancy of the light, the season of the year, the time of the day, and other minor circumstances. A few seconds, even in the room, are mostly quite sufficient. The exact number is easily learned from the conditions of the case; and then the exposure afterward can be regulated by counting. The plate is next withdrawn from the plate-holder in the dark-room; it contains no visible image; this is made to appear by proceeding to the

Fourth Operation, or Developing by the Vapor of Mercury.

A cast-iron box is prepared for this purpose, capable of being well closed after the plate is introduced. It contains mercury at the bottom, which is kept at the temperature of from 120° to 150° Fahrenheit, by means of a lamp with a small flame capable of graduation, and a thermometer attached to the box with the bulb in the mercury. A couple of ounces of mercury will be sufficient at once for ordinary portraiture. In two or three minutes the development will be complete. At intervals the plate maybe examined to see the progress of development; but this examination must be made with great care, for the film is easily fogged by exposure to diffused light. If the time of exposure has been too long, the whole image will be fogged and indistinct; whereas if it has been too short, the high lights alone will be developed, while the rest will undergo no change whatever. Supposing the picture to possess the proper gradation of light and shade, it is then ready for the

Fifth Operation, or the Fixing of the Developed Image.

The film is still very sensitive, and the picture in a few minutes would be irremediably spoiled, unless the sensitive character of the film be annihilated. This is effected by plunging the plate immediately into the fixing solution, which must be preserved in a very clean condition by continual filtration after each operation. The fixing solution consists of

Hyposulphite of soda, 2 drachms.
Distilled or rain-water, 2½ ounces.

Agitate the plate in this solution for a few seconds, until the iodizing is entirely removed, and then wash the plate in distilled water. In all operations of washing and fixing, use only filtered materials, for small particles of dust are very visible on the dried plates; use, especially, very pure water, because ordinary water contains salts, which are left as a deposit on the plates when dried. After the fixed plate is well washed proceed to the final or

Sixth Operation, or the Toning with Gold.

In the first place make a ledge round the plate in the opposite direction, so as to form a miniature dish with the picture at the bottom; or cat off the former ledges entirely, and holding the plate by one of its corners with a pair of pliers, pour upon the surface of the picture, held horizontally, as much of the following gold solution as it will hold without flowing over the edges

Toning Solution.

No. 1. Chloride of gold, 1 grain.
Distilled water, 1 ounce.
No. 2. Hyposulphite of soda, 4 grains.
Distilled water, 1 ounce.

Dissolve and pour the gold solution into the hyposulphite of soda, and mix well together. Next light a spirit-lamp with a large wick, and holding the pliers and plate in the left hand, play beneath the plate containing the toning solution with the flame of the lamp held in the right hand. Do not allow the flame to play upon the same spot; move it about, bubbles will soon begin to arise, and the picture will soon begin to assume a much more agreeable tone. Take care to have an excess of gold solution all the time upon the plate, otherwise, if it fails on a certain part during the operation of gilding, a stain will be produced that can not be removed by any subsequent treatment. Use also a large flame, to produce rapid action; prolonged action fogs the picture. When the tone of the picture is satisfactory, immerse the plate at once in a basin of water, and wash well at the top; afterward pour over the plate two or three times, distilled water, and then dry the plate; beginning at the upper edge with the application of the flame of the lamp, proceed downward, as the film dries, blowing off the excess of water as you proceed, or absorbing it with a sponge from the pendent edge and corners, until the whole surface is dry.

Daguerreotypes may be touched up with color like any other photographs, where desired. It must be confessed, however, that a well-toned daguerreotype picture looks best unadorned with either color or tinsel.

Home ~ Library ~ Science ~ Technology ~ Gallery ~ Video ~ Forum ~ About ~ Search