The manufacture of dry plates has now reached such a state of perfection that the purchaser may procure them of every grade of sensitiveness, each of the several grades of a perfect uniformity and all of them very free from imperfections and blemishes. And also the prices have been so reduced of late that the incentive to manufacture on the part of individuals for their own use is almost entirely lacking. However, there may be found a certain interest and fascination in preparing plates for one's own use, which would prompt some to incur the outlay and trouble incidental to such a course, and for those full instructions and formulas may be found in the first part of this book.
It will, however, be found, after due trial, that for work of importance, and where certainty of results is desired, it will be better to procure the plates of some maker of established reputation, and of such a grade of sensitiveness as will be most suitable for the work in hand.
Certain makers of dry plates use the Sensitometer to ascertain the degree of rapidity of each and every emulsion produced in their works. The ascertained degree of rapidity is indicated on each box of plates by the Sensitometer number - the higher the number, the more sensitive the plate. The highest numbers attained up to this time are from 20 to 25, and these numbers would indicate a very high degree of sensitiveness, such as render plates of 23 to 25 quite suitable for work requiring the shortest possible, in fact, instantaneous, exposures., such as bodies in motion across the plane of focus. Views of still life are better made with plates of a lesser degree of rapidity.
The handling of dry plates of such extreme rapidity requires great care. The boxes should never be opened, even the outer wrappings should not be removed, except in the darkened room and by such a light as that produced by Carbutt's dry plate lantern or some similar device. When plates are taken from the boxes for the purpose of fitting the holders, they will be found to have one clear, smooth and shining surface. This is the back of the plate and is clear glass; the other surface is of the same color, but of a mat or dead color, not reflecting so much light. This is the sensitive surface, and before being placed in the holder or shield it should be brushed with a soft, flat camel's hair blender, to remove any dust that may be attached to the surface. This brush should be used for no other purpose; and should be used without pressure, merely touching the surface of the plate. The plate may then be put in the plate carrier of the shield, with the sensitive surface outward, and when the carrier is run into its place in the holder, the sensitive surface is next the slide or door. It is of some importance that attention should be given to this manipulation, as it not unfrequently occurs that the wrong side of the plate is turned outward and the image, when the plate is exposed, is made through the glass and against the back of the film, and is reversed and thus rendered worthless, even should a good impression have been secured.
The holders or shields for dry plates for out-door work are always - except in the largest sizes - made double, each holder containing two plates.
Anthony's Patent Perfect Double Dry Plate Holders Or Shields.
The diagram exhibits the plate holder, 3, with the plate carrier, 1, partly drawn out; the slide or door corresponding to 2 is withdrawn to show the interior of the holder, 3, and the spring that presses the plate into focus, when pushed into the carrier, 1. This carrier presents the same appearance on the other side and will hold two plates. When filled with plates, it is pushed into its place in the holder, 3, and the brass loops or fasteners, 4, are pressed down flat, thus securely holding it in place. When the holder is put in place at the back of the Camera the slide, 2, next the box, is pulled out quickly and in a perfectly level position, so that the spring shut-off may close instantly and permit no light to enter the opening. The lens must be covered before the slide is pulled out. The exposure is then made and the slide is returned to its place in the same manner, carefully observing that one corner is not entered first, but the end must be inserted into the groove squarely and pushed quickly home. If another exposure is to be made immediately, the holder is removed and the opposite side placed next the box, and the same process is repeated, covering the lens, removing the slide, make the exposure by removing the cover of the lens and replacing it, then return the slide to its place. When a second exposure is not made at once, with a pencil or in some other manner mark the side that has been exposed, to prevent any mistake. When both plates are exposed, return the holder to the carrying case and take the next, if you carry more than one. Usually a half dozen holders are carried, which gives command of one dozen plates, which should be quite enough for one outing.
Having exposed the plates, the holders are returned to the carrying case, and should not be removed therefrom until they are taken into the dark room for development, when, by the aid of some safe light, they may be removed from the holders, one at a time, and developed, or all taken out and put into a negative box, to be ready for development when convenient.