The History and Practice of the Art of Photography [33]
more and sometimes less satisfactory, in consequence of small and accidental variations in the proportions employed. It happens sometimes that the chloride of silver formed on the surface of the paper is disposed to blacken of itself, without any exposure to light. This shows that the attempt to give it sensibility has been carried too far. The object is, to approach as nearly to this condition as possible without reaching it; so that the preparation may be in a state ready to yield to the slightest extraneous force, such as the feeblest effect of light.
Cooper's Method.--Soak the paper in a boiling hot solution of chlorate of potash (the strength matters not) for a few minutes; then take it out, dry it, and wet it with a brush, on one side only, dipped in a solution of nitrate of silver, sixty grains to an ounce of distilled water, or, if not required to be so sensitive, thirty grains to the ounce will do. This paper possesses a great advantage over any other, for the image can be fixed by mere washing. It is, however, very apt to become discolored even in the washing, or shortly afterwards, and is, besides, not so sensitive, nor does it become so dark as that made according to Mr. Talbot's method.
Daguerre's Method.--Immerse the paper in hydrochloric (or as it is more commonly called, muriatic) ether, which has been kept sufficiently long to become acid; the paper is then carefully and completely dried, as this is essential to its proper preparation. It is then dipped into a solution of nitrate of silver, and dried without artificial heat in a room from which every ray of light is carefully excluded. By this process it acquires a very remarkable facility in being blackened on a very slight exposure to light, even when the latter is by no means intense. The paper, however, rapidly loses its extreme sensitiveness to light, and finally becomes no more impressionable by the solar beams than common nitrate paper.
Bromide Paper.--Of all common photographic paper, the best, because the least troublesome in making, and the most satisfactory in result, is that which is termed bromine paper, and which is thus prepared:--Dissolve one hundred grains of bromide of potassium in one ounce of distilled water, and soak the paper in this solution. Take off the superfluous moisture, by means of your bibulous paper, and when nearly dry, brush it over on one side only, with a solution of one hundred grains of nitrate of silver to an ounce of distilled water. The paper should then be dried in a dark room, and, if required to be very sensitive, should a second time be brushed over with the nitrate of silver solution.
In preparing the papers mentioned above, there are two circumstances which require particular attention. In the first place, it is necessary to mark the paper on the side spread with the solutions of nitrate of silver, near one of the extreme corners. This answers two purposes: in the first place it serves to inform the experimemtalist of the sensitive surface; and secondly, it will be a guide as to which portion of the papers has been handled during the application of the solution, as the impress of the fingers will probably come out upon the photograph. The second caution is, that the application of the sensitive solution (nitrate of silver,) and the subsequent drying of the paper, must be always conducted in a perfectly dark room, the light of a candle alone being used.
III. PHOTOGENIC PROCESS ON PAPER.--Method.--The simplest mode is to procure a flat board and a square of glass, larger in size than the object intended to be copied. On the board place the photographic paper [hipho_29.gif] with the prepared side upwards, and upon it the object to be copied; over both lay the glass and secure them so that they are in close connection by means of binding screws or clamps, similar to g. g. fig. 29. Should the object to be copied be of unequal thickness, such as a leaf, grass, &c., it will be necessary to place on the board, first, a soft cushion, which may be made of a piece of fine flannel and cotton wool. By
Cooper's Method.--Soak the paper in a boiling hot solution of chlorate of potash (the strength matters not) for a few minutes; then take it out, dry it, and wet it with a brush, on one side only, dipped in a solution of nitrate of silver, sixty grains to an ounce of distilled water, or, if not required to be so sensitive, thirty grains to the ounce will do. This paper possesses a great advantage over any other, for the image can be fixed by mere washing. It is, however, very apt to become discolored even in the washing, or shortly afterwards, and is, besides, not so sensitive, nor does it become so dark as that made according to Mr. Talbot's method.
Daguerre's Method.--Immerse the paper in hydrochloric (or as it is more commonly called, muriatic) ether, which has been kept sufficiently long to become acid; the paper is then carefully and completely dried, as this is essential to its proper preparation. It is then dipped into a solution of nitrate of silver, and dried without artificial heat in a room from which every ray of light is carefully excluded. By this process it acquires a very remarkable facility in being blackened on a very slight exposure to light, even when the latter is by no means intense. The paper, however, rapidly loses its extreme sensitiveness to light, and finally becomes no more impressionable by the solar beams than common nitrate paper.
Bromide Paper.--Of all common photographic paper, the best, because the least troublesome in making, and the most satisfactory in result, is that which is termed bromine paper, and which is thus prepared:--Dissolve one hundred grains of bromide of potassium in one ounce of distilled water, and soak the paper in this solution. Take off the superfluous moisture, by means of your bibulous paper, and when nearly dry, brush it over on one side only, with a solution of one hundred grains of nitrate of silver to an ounce of distilled water. The paper should then be dried in a dark room, and, if required to be very sensitive, should a second time be brushed over with the nitrate of silver solution.
In preparing the papers mentioned above, there are two circumstances which require particular attention. In the first place, it is necessary to mark the paper on the side spread with the solutions of nitrate of silver, near one of the extreme corners. This answers two purposes: in the first place it serves to inform the experimemtalist of the sensitive surface; and secondly, it will be a guide as to which portion of the papers has been handled during the application of the solution, as the impress of the fingers will probably come out upon the photograph. The second caution is, that the application of the sensitive solution (nitrate of silver,) and the subsequent drying of the paper, must be always conducted in a perfectly dark room, the light of a candle alone being used.
III. PHOTOGENIC PROCESS ON PAPER.--Method.--The simplest mode is to procure a flat board and a square of glass, larger in size than the object intended to be copied. On the board place the photographic paper [hipho_29.gif] with the prepared side upwards, and upon it the object to be copied; over both lay the glass and secure them so that they are in close connection by means of binding screws or clamps, similar to g. g. fig. 29. Should the object to be copied be of unequal thickness, such as a leaf, grass, &c., it will be necessary to place on the board, first, a soft cushion, which may be made of a piece of fine flannel and cotton wool. By