In making up a bath, equal quantities of (a) and (6) are mixed, plenty of chalk being added, letting the whole stand for 3-5 hours before use. With some samples of this paper, the bath can be used at once; but with other sheets, this is not the case, a deposit of gold taking place over the whole prints, and destroying the purity of the whites. It is better, therefore, to err on the safe side by making up the bath a considerable time before it is required, and thus be assured of having a uniformity in one's photographs. When you have many prints to tone, use 2 flat dishes capable of holding, say, 1 doz. prints each. Filter the solution into these dishes to the depth of 1/4 in.; were the liquid deeper, the prints would not keep flat. Wash in 3 changes of water; and as the prints generally curl up into tubes, open each of them separately in the water, so as to get the surface uniformly washed. It this is not done, and done in each separate dish of clean water, uneven toning will be sure to take place.
When the prints have been properly washed with a quick but gentle movement, open up each picture, and lay it flat in the bath face downward; and when the dish is full, begin at the first and turn it over, brushing the face with a camel-hair brush, and continue the process until the whole have been so treated, afterwards turning them back again into their former position, and so on without cessation, until the prints are ready to leave the bath. When stains occur in the course of toning, lift the print out of the solution, dip the brush in alcohol, and rub the spot slightly. Then immerse the print again, when it will be found that the stain has disappeared, and the print has been saved.
When fixing the prints, the same care is required in laying them separately in the fixing solution, turning them over, and keeping them in motion until they are fixed, which is completed, when the fixing bath is new, in 3-5 minutes. When removed from the bath, the prints are immersed for a few minutes in 3 or 4 changes of water, and put under the tap for 1-2 hours. The water is then shut off, and they are left all night, and throughout the next day until the afternoon; the water is changed now and again. The prints are then trimmed and mounted. The system in use amongst the many of the profession, of cutting the prints to the exact size wanted before toning them, cannot be readily adopted with collodio-chloride pictures. In their case the paper should always be a little larger than is necessary, allowing not less than 1/8 in. to be cut off all round after the prints have been toned, fixed, and washed. The reason for this is that the edges of the prints are very curly, add the film becomes frayed in the course of washing; by cutting away this frayed curly part, they are more easily and neatly mounted.
As it is impossible to lay these prints upon blotting-paper and dry them in a flat state without cracking the surface, another method has to be put in practice for the purpose of trimming them. Use a piece of thin plate glass, cut to the exact size of what the carte-de-visite print should be, the edges being ground and the corners slightly rounded, so as not to scratch the picture. If the prints are more than ordinarily curly, open them underneath the water, and lay the sheet of glass upon the face, and then lift both of them out of the water at once, the moisture between them enabling you to move and adjust the glass over the print with the greatest ease. Then, with a pair of Iong-bladed scissors, cut along the 4 edges of the glass, and thus secure a straight clean-cut print, without damaging the surface of the photograph.
The medium for mounting is starch, carefully boiled, as thick as possible. It is, while still warm, poured into the centre of a muslin cloth, the corners of which are drawn together and held firmly with the left hand, while the right hand presses the bag and causes the pure starch to exude through the interstices of the cloth - the result being a paste perfectly free from gritty matter, and of the right consistence for mounting.
A sheet of thick plate glass is covered with a damp cloth, and the prints are lifted from the dish and laid upon it in a wet condition, the water on the face of the prints and the damp cloth preventing them from curling. They are then pressed quite flat with another cloth, and dried before they are starched.
After the prints are mounted, dried, and spotted out, roll them upon a hot steel plate; they are then put up in dozens into paper and laid upon the machine plate, and when warm are rubbed over with "Salomon paste," which gives them a richness and transparency they would not otherwise possess.
If desired, these photographs may very easily be covered with "Mawson's print varnish" or "enamel collodion" by coating them with a camel-hair brush of the same breadth as the card. Some think they are more beautiful and artistic when simply finished with wax paste. At first, the manufacturers of collodio-chloride papers were not so careful as they are now regarding the basis on which the collodion film rests; nay, there is reason to believe that sheets of albumenised paper were then used as a support for the emulsion. In such a case, the prints made from those sheets are liable to fade.
In the following note, the author's aim has been principally directed to prepare films by the use of a collodion and bath, combining, with long keeping properties, adaptability to the ordinary wet process worked with iron development. The great susceptibility of highly sensitive films to injury from weak luminous radiations during preparation, exposure, and development, render reliable plates of moderate sensibility a perfect desideratum. Such, when worked with others of high sensibility, if easily prepared and developed away from a specially constructed laboratory, constitute essential requisites for the amateur landscape photographer.
Although any collodion of recognised standard excellence for iron development is perfectly suitable, yet in the manufacture of pyroxyline, the 3 to 1 proportion of sulphuric to nitric acid, originally recommended in the patent for explosive cotton, and subsequently ably advocated for the soluble varieties, is not found to be the best. The employment of a larger quantity of nitric acid to the sulphuric, yields a better result for the soluble kinds. The following formula is based, therefore, on this consideration : -
Sulphuric acid, sp. gr. 1. 84 6 fl. oz. Nitric „ „ 1.42 3 "
Water ........5 3/4 fl. dr.
Cotton ...... 150 gr.
Temperature, 155° F., descending to 145° F. Time of immersion, 10 minutes. The double temperature given signifies that, at the time of the' introduction of the cotton, the acids should be at 155° F., and the allowable decline must not exceed 10°. Mix 6 fl. dr. of a plain collodion, made by dissolving 5-6 gr. of the above pyroxyline in a mixture of 4 fl. dr. methylated ether, sp. gr.720, and 2 fl. dr. pure alcohol, sp. gr. 820, with a bromo-iodising solution made as follows: -
Sodium iodide .. .. 6 gr.
Cadmium bromide .. 4 gr.
Iodine........ 1/2 gr.
Guaiacum ...... 1/4 gr..
Alcohol, sp. gr. 820 .. 2 fl. dr.
Before coating the plate, apply a substratum consisting of 1 oz. liquid albumen and 30 minims liquor ammoniae, sp. gr. 959, dissolved in 1 pint water. After the plate is coated, excited in an ordinary argentic nitric bath, and removed therefrom, it is to be freely washed in ordinary water kept in motion, and then treated with the following preservative, poured on and off the film twice or thrice from different parts.
Albumen ...... 1 fl. oz.
Glucose solution (raisins 1 part, water 5 parts) 2 " Water........ 3 „ Liquor ammoniae, sp. gr. 959...... 15 m.
Ammonium chloride .. 3 gr.
Ammonium bromide .. 1/2 gr.
The film is again to be freely washed with ordinary filtered water, and covered with a 3-gr. solution of gallic acid, and evenly dried. The back of the glass, as a matter of precaution against very trying conditions, rather than as an ordinary necessity, should be covered with a non-actinic colour. Burnt sienna ground in water and mixed with a little gum mucilage, constitutes a good medium for the purpose.
At any convenient interval after exposure, the film is washed, and developed with a suitable quantity of solution made in the following proportions: -
Water........ 4 fl. dr.
Pyrogallic acid (64 gr. dissolved in 1 fl. oz. alcohol, 805) .. .. 15 m. Potassium bromide (16 gr. in 1 oz. water) .. 15 m. Sodium carbonate (64 gr. in 1 ox. water) .. 15 m.
Only 5 m. of the potassium bromide should be added in the first instance, and the remainder upon the earliest indication of an image. As soon as the general details of the picture become faintly visible by reflected light, the alkaline developer should be removed, and a 3-gr. solution of citric acid applied. The intensification may then be effected with pyrogallic acid, citric acid, and argentic nitrate, and the unreduced salts dissolved away with sodium hyposulphite as usual. (T. Sebastian Davis.)