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"I shall endeavor to lay down in as comprehensive a manner as possible the method by which I have been enabled to produce the most satisfactory results. I use a Smee's battery (another kind will do). After filling the cell, of common size, nearly full with water; add about quarter of an ounce of sulphuric acid. Mix this well, and let it stand for about three hours, or until the action of the battery becomes weak, when it is in order to work with a very uniform action. Put one pound of sulphate of copper in one quart of water; stir it until the sulphate of copper is all dissolved, and then add one half ounce of sulphuric acid and a quarter of an ounce of nitric acid. This solution, well mixed, should be filtered, and it is ready for use. It is very important that the solution should be kept clean, clear, and free from all foreign substance. The above quantity of this solution will be found sufficient for electrotyping a dozen of the sixth-size plates. When it is required to be strengthened, it is only necessary to add a little of the sulphate of copper.
"With the battery prepared as above, and the solution of sulphate of copper in a vessel of proper dimensions to receive your plate, connect the galvanic current, and immerse the impressioned plate, letting it remain until a thin film of copper has been formed, then the battery can be strengthened, and the impression will be of sufficient thickness to be removed in from eight to twelve hours. An old Daguerreotype plate attached to the opposite pole of the battery (copper side towards the face of the plate to be electrotyped), will answer the same purpose as the silver-plate.
"The great difficulty in taking an electrotype impression, and preserving the original, has been attributed to the battery being too powerful. I am led to believe from practice that the principal difficulty has been in the Daguerreotype plate itself, for if we use an impression that has been taken but a few days, and taken in the usual way, we will find it difficult to succeed without spoiling both the copy and original, and so also with an old impression.
"I have found the most certain method to be as follows:-- Coat the Daguerreotype plate as usual, except use less of the accelerators, the proportion of iodine coating being greater, of course the time of exposure in the camera will be lengthened. Mercurialize it at about a temperature requiring to develop the image, from six to eight minutes, at least. Gilding the Daguerreotype has much to do towards producing a good electrotype copy. This should be done by applying a little heat, and gilding very slowly, giving a coating of gold with the greatest possible uniformity. By this method, I have been enabled to produce any number of proofs. I have produced a dozen from one impression, and it remains as perfect as when first taken.
"By a little judgment and care the operator will be enabled to produce the electrotype copy of the Daguerreotype plate without any difficulty. The electrotype copy should be immediately put under a glass and sealed in the same manner as the ordinary Daguerreotype."
This process is patented in the United States, by J. A. Whipple, of Boston, and of course no honorable person will use it for his own benefit without purchasing a right.
A white back-ground is generally employed, the object being to blur the lower portion of the plate, leaving the head of the subject in relief. Every Daguerreotypist is familiar with the fact that a motion of any body between the camera and the sitter will cause a "blur." Cut a piece of thin paper and scallop it, making a semicircle. This is kept straight by means of a wire frame, and it is to be moved in front of the lower part of the body of the sitter during the time of exposure of the plate in the camera. Develop over mercury as usual, and the result will be a crayon Daguerreotype.
Another method is to have a wheel with a hole cut through it of a diameter of about 12 inches. This hole is so cut as to leave teeth resembling those of a large saw. This wheel is so arranged that it can be turned around, which should be done during the time of exposure in the camera. It must be placed between the camera and the sitter, and at such a distance from the camera as to allow such proportion of the body of the sitter be seen upon the ground-glass as is desired. It will be readily seen that by turning this wheel during the operation will produce the same result as the paper being moved in the other method. The teeth make the "blur." The side of the wheel towards the camera may be black, by which means the result will be a dark instead of a light border.
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