BY GEO. M. HOPKINS.
DAGUERREOTYPY, although one of the most notable inventions of the present century, is already obsolete. It is nearly forgotten by those who practiced it, and is not preserved in all its details in the literature of photography. It is undoubtedly safe to say that a very small proportion of professional photographers, and a still smaller proportion of amateurs, have any practical knowledge of the subject. The writer, though never a professional daguerreotypist or photographer, very early in life acquired a practical knowledge of photography in the days when daguerreotypy was at its best. The interest then awakened has since been maintained through every phase of the growth and development of the art; and recently, depending on memory alone, the writer has extemporized apparatus, and successfully carried out the daguerreotype process.
It will be remembered that Neipce and Daguerre sought independently of each other for a method of producing sun pictures. Neipce at first employed plates coated with bitumen. He formed a partnership with Daguerre in 1829, but died before the invention now known as daguerreotypy was perfected.
After the death of Neipce, Daguerre improved the art to such an extent that Neipce's son allowed it to go under its present name. Both inventors received annuities from the government for giving the invention to the public.
In this country the art was first practiced by Morse, and was improved by Draper soon after it was introduced here.
Daguerreotypy was very simple, easily understood, and easily managed, and was learned by many who found it a light business, requiring little capital and returning large profits.
The plates employed were copper faced with silver. The metal was hard rolled, and the plates, as received from the manufacturers, were flat and quite smooth, but not polished. The first step toward the preparation of the plate for use was to clip the corners and turn down the edges slightly, in a machine designed for the purpose, to bring the sharp edges of the plate out of reach of the buff employed in producing the necessary polish.
The plate was held, for scouring, in a block having clips on diagonally opposite corners for engaging the corners of the plate. One of the clips was made adjustable, to admit of readily changing the plates. The block was mounted pivotally on a support clamped to the table, as shown in Fig. 1.
The scouring was effected by sprinkling on the plate the finest rottenstone from a bottle having a thin muslin cover over its mouth, and the rottenstone as well as the square of Canton flannel with which it was applied was moistened with dilute alcohol. The center of the Canton flannel square was then clasped between twow of the fingers, and moved round and round with a gyratory motion until the plate acquired a fine dead-smooth surface. The last traces of rottenstone were removed by means of a clean square of flannel. The plate was then transferred to a block mounted on a swinging support, and buffed by the vigorous application of a straight or curved hand buff formed of a board about four inches wide and thirty inches long, padded with four or five thickness of Canton flannel, and covered with buckskin charged with the finest rouge. Scrupulous cleanliness was imperative in every step of the process.
The buffs were kept clean and dry, when not in use, by inclosing them in a sort of vertical tin oven, which was warmed by a small spirit lamp. A careful operator would prepare a plate having a bright black polish without a visible scratch, while an incompetent or careless man would fail in this part of the process, and would prepare plates full of transverse grooves and scratches. The beauty of the picture depended very much on the careful preparation of the plate.
Occasionally, a buff would in some manner receive particles of matter which would cause it to scratch the plate. The remedy consisted in scraping the face of the buckskin, and brushing it thoroughly with a stiff bristle brush, generally a hair brush devoted especially to this use. The buff was then recharged by dusting on rouge from a muslin bag.
When the rotary buff wheel was adopted, it insured rapid work, but it was otherwise no improvement over the hand buff. At first, the wheels were made cylindrical, but that incurred the necessity of an objectionable seam or joint where the leather lapped. The conical buff wheel (Fig.3) allowed the use of a whole skin, thereby dispensing with the seam.
After buffing, the plate was taken to the dark room to be sensitized. The room had a side window, generally covered with yellow tissue paper, for the examination of the plate during the process. The room contained two coating boxes, one for iodine, the other for bromine. The construction of these boxes is clearly shown in Fig. 9, which is a longitudinal section of one of them. The two boxes were alike except in the matter of depth; the bromine box being about twice as deep as the iodine box.
Each box contained a rectangular glass jar having ground edges. In the top of the box was fitted a slide more that twice as long as the box. In the under surface of one end of the slide was fitted a plate of glass, adapted to close the top of the jar, and in the opposite end of the slide was formed an aperture, furnished with a rebate for receiving the plate. Upon the top of the slide was arranged a spring-pressed board, which held the slide down upon the top of the jar.
On the bottom of the jar of the iodine box were strewn the scales of iodine, and in the bromine box was placed quicklime charged with bromine. The bromine was added to the lime drop by drop, and the lime occasionally shaken until it assumed a bright pink hue bordering on orange. The lime was thus prepared in a glass stoppered jar, and transferred to the jar of the coating box as needed; one inch being about the depth required in the coating box. The polished plate was placed face downward first in the slide of the iodine box, and coated by pushing in the slide so as to bring the plate over the iodine in the jar. It was there exposed to the vapor of iodine until it acquired a rich straw color, the plate being removed and examined by the light of the paper window, and replaced if necessary to deepen the color. The plate was then in a similar manner subjected to the fumes of the bromine until it became of a dark orange color. It was then returned to the iodine box and further coated until it acquired a deep brownish orange color bordering on purple. The time required for coating the plate depended upon the temperature of the dark room. The process was very rapid in a warm room and quite slow in a cool room.
The plate, rendered sensitive to the light by the thin layer of bromo-iodide of sliver, was placed in a plate holder, and exposed in a camera according to the well known method. The time of exposure was much longer than that of modern photography. A great deal depended on the quality of the lenses of the camera. The exposure in the best cameras was reasonably short. The old time gallery, with its antiquated camera and fixtures, and the dark room with the appurtenances, are faithfully represented in the engraving.
After exposure, the plate was taken to another dark room for development. It was placed face downward over a flaring iron vessel, in the bottom of which there was a small quantity of pure mercury. The mercury was maintained at a temperature of 120 to 130 degrees Fah. by means of a small spirit lamp. The temperature was measured by a thermometer attached to the side of the vessel. The plate was raised occasionally and examined by the light of a taper, until the picture was fully brought out, when it was removed from the mercury bath and fixed.*
The fixing consisted merely in flowing over the plate repeatedly a solution of hyposulphite of soda, having sufficient strength to remove in about half a minute all the bromo-iodide of silver not acted upon by light. The plate was then thoroughly washed, and afterward gilded or toned by pouring upon it a weak solution of chloride of gold and heating it gently by means of a spirit lamp until a thin film of gold was deposited upon the plate and the picture attained the desired tone. The plate was then washed in clean water, and finally dried evenly and quickly over a spirit lamp.
This operation added to the strength and beauty of the picture, and also served to protect the surface of the plate to a great extent against the action of gases.
The finished picture was protected by a cover glass, and
the edges of the glass and plate were securely sealed by a strip of paper
attached by means of an adhesive coating.
* A fortunate accident led to the discovery of the development of the photographic impression by means of the vapor of mercury. Previous to this discovery, the image was brought out by a long continued exposure in the camera. Daguerre on one occasion placed some under-exposed plates, which were considered useless, in a closet in which there were chemicals. Afterward, happening to look at the plates, he was astonished to find an image upon them. After taking one chemical after another from the closet until apparently all were removed, the images on his plates were still mysteriously developed. At length he discovered on the floor an overlooked dish of mercury, and the mystery was solved. He ascertained that the effects produced by the mercury vapor spontaneously given off could be secured at will by suitable apparatus.
(Transcriber's note: This anecdote of Daguerre's discovery of mercury development is generally considered spurious by modern photo-historians. --Gary W. Ewer, 1995)