This section is from the book "Complete Self-Instructing Library Of Practical Photography", by J. B. Schriever. Also available from Amazon: Complete Self-Instructing Library Of Practical Photography.
Cramer's Double-Coated Non-Halation Plates. First coated with a slow, and for a second time with a rapid emulsion. Specially made to prevent halation, and hence recommended for photographing interiors in which strong light entering through the windows has to be contended with, and for landscapes, white draperies and all objects where there exists a strong contrast between light and shade.
625. Use a rather dilute developer for double-coated plates, so that the development can be prolonged sufficiently to affect the lower film, which will take about double the usual time. Rinse for two minutes, and fix in acid-fixing and hardening bath, leaving them in the bath until entirely fixed, which, owing to the thickness of the film, will take more than double the time of a single coated plate. If the plate is taken from the bath before it is fixed, stain will ensue. Final washing must be thorough.
626. Care should be taken that the temperature of the developer, water used for rinsing, and fixing bath be the same, and that the acid-fixing and hardening bath be fresh and properly made. These precautions will obviate any danger of the upper and lower films separating.
627. The Double-Coated are made in the following brands: - Crown, Banner X and Isochromatic Instantaneous, Medium and Slow.
Cramer Stripping Plates. - Made in Crown, Banner X, Isochromatic or Contrast Brands.
Directions For Use. The manner of manipulating these plates differs but little from that of the ordinary dry plate, the development, fixing, hardening and washing being the same. But the temperature of the developer should not be higher than sixty or sixty-five degrees Fahrenheit, and a fresh cool acid-fixing and hardening bath should be used. Great care, however, should be taken to prevent an injury to the surface of the film during these operations, as the introduction of fluids between the glass and film would injure the latter. After the final washing the surface of the plate should be flowed with a mixture composed of one part glycerine and thirty parts water. Cut a piece of gelatine tissue, somewhat larger than the plate, soak this in this solution, and bring it in contact with the wet surface of the film. Air-bells between the film and tissue should be carefully expelled by the use of a soft damp sponge, or a squeegee. The over-lapping ends should now be pasted to the back of the negative with stiff starch paste, and the whole placed in the rack to dry. It may then be flowed with plain collodion. To strip the film, cut through it all around the edge of the plate about one-fourth inch in, and remove it with a steady pull. Any stoppage during this operation will cause marks on the negative and should be avoided. The stripped negatives should be preserved between the leaves of a book. They can be printed from either side.
629. For transferring to another sheet of glass harden the fixed and washed negative for ten minutes in a bath composed of Formalin one ounce, water ten ounces, glycerine one-half ounce, then rinse free from all greasy appearance and dry. Cut through edges of film, and remove from the glass as directed above. Then place the film in a warm solution (about ninety degrees Fahrenheit), composed of hard gelatine one ounce, swelled and then dissolved in fifteen ounces of warm water, with the addition of one ounce of glycerine, until the film is limp, then transfer to the clean sheet of glass and gently remove all air-bells with a soft sponge or squeegee, working from the center of the film.
630. Cramer X-Ray Plates, are specially made by the Cramer Co. for making X-Ray negatives.
631. While any ordinary plate is of course affected by the X-Rays, yet they do not possess those properties that have built up the reputation of the Cramer X-Ray plate among experts, and X-Ray specialists.
632. X-Ray plates should be kept in a lead lined case to protect them from the influence of the rays. Nor should plates before or after exposure be left for more than a short time in the envelopes, as prolonged contact with the paper will injure or spoil the plate. When placing plates in the envelopes keep well away from the dark room light, and put the film side of the plate towards the face of the black envelope, and insert the black envelope flap end down, with the face of the black envelope towards the face of the yellow envelope. Even when in the double envelopes the plates should not be exposed to the influence of strong daylight, but protected by a paste board box, if they are to be carried out of doors, to avoid danger of fogging. Never take a plate near an X-Ray machine when the tube is turned on or it will fog. It is impossible to give any directions for duration of exposure needed, this depending on whether a coil or a static machine is used, and their size and power, as well as on the kind and quality of tube used. Generally speaking, static machines have been superseded by coils on account of the former's lack of power, they only being suitable for light work like the extremities. Most workers believe that a tube of rather low vacuum and high penetrating power makes better negatives than one of high vacuum and high penetrating power, as the latter penetrates the bones so much that there is not sufficient contrast in the negative. In making X-Ray exposures, err on the side of over, rather than under-exposure, and for development use a strong concentrated developer with a good dose of bromide of potassium, and carry development as far as possible (after-reduction is easy if necessary). Either of the X-Ray developers given among formulae in this article will give good results, the most desirable negative being one of great intensity in the easily penetrated parts, good detail in the tissues with plenty of contrast between them and the bones.
633. Fix the plates in a fresh acid-fixing and hardening bath, leaving them in this bath long enough to harden the film way through.
Warning : - Operators should not expose their hands or bodies to the influence of the rays for repeated exposures will result in burns which, as far as known, cannot be healed.
A TOKIO WATERWAY Study No. 13, See Page 345 Tokio, Japan Wm. H. Phillips, Liverpool, Ohio.