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."CRAYON DAGUERREOTYPES.
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.
ILLUMINATED DAGUERREOTYPES.
This process is also patented, and the remarks on the preceding subject will apply in this case. The plate is prepared and exposed as in the usual method of the Daguerreotype. A white back-ground is employed.
Let the head of the sitter come in the middle of the plate, and before exposing it to the vapors of mercury, put a small mat or diaphragm, having a small hole through it, over or directly on the surface of the plate.
This diaphragm should be bevelled, and the bevel should be towards the surface of the plate; this, in order to prevent too sharp a line on the impression.
It will be readily seen that if an impressioned plate so covered is placed over the mercury, it will be developed on such portions only as are exposed.
The principle is so familiar that further explanations are unnecessary.
NATURAL COLORS IN HELIOGRAPHY.
This subject is worthy the attention of every operator. The following process is so plain and easy of trial that any Daguerreotypist can try it.
This is as given by Mr. James Campbell, and was published in Humphrey's Journal of the Daguerreotype and Photographic Arts, vol. 5, page 11.
Mr. Campbell has done much to further the process announced by M. Neipce, and his experiments have proved highly successful.
The following is submitted as worthy of trial:
"The proper preparation of the chloridated plate, to enable it to receive colored impressions is an object of the first importance to those wishing to experiment on it, and consequently requires particular notice.
The plate may be prepared by making it the positive pole of a battery, and letting it at the same time be immersed in chlorine water.
The negative pole should be a slip of platinum. All the colors may be produced from a plate so prepared if the chlorine and water are in the right proportions; but generally one color or the other predominates, according to the amount of chlorine in the liquid. By adding the chlorides of strontian, uranium, potassium, sodium, iron, or copper to the liquid, various effects may be produced, and these bodies will be found to produce the same color on the plate that their flame gives to alcohol.
"The honor of this discovery is due to M. Neipce.
Copper gives a variegated flame; hence many colors may be impressed on a plate prepared with a solution of its chloride.
"M. Neipce recommends a solution of the mixed chlorides of copper and iron, and it is with these, that I have been most successful.
As the chlorides of copper and iron are not much used in the arts, they are not generally found for sale in the shops; and it may be well to furnish those not much versed in chemistry with an easy method of preparing them.
"They may be made directly from either metal by dissolving it in hydrochloric acid; but they may be formed by a cheaper method, and by which also the acid fumes are avoided.
"Sulphate of iron or copper, or both together, may be dissolved in water and then neutralized with common crude potash, or its carbonate or bicarbonate--known commonly as pearlash and saleratus.
