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.
Dulling The Surface Of Dark-Painted Machinery. Mix white lead with turpentine to the consistency of thin cream, with sufficient lampblack added to form a light slate color, and then add one-sixth the bulk of Japanese gold size to make the mixture adhere. Paint the machinery over with this. After the photograph has been taken the color can be readily removed with "cotton waste" moistened with turpentine or benzine. This paint should be applied to all frame-work where dark paint is usually employed.
Chalking Machinery. On the majority of castings and pieces of machinery the maker's name-plate will be found, bolted on, or perhaps cast in some part of the tool or machine. It is very important that these raised letters be reproduced as strongly as possible. The most effective way to prepare these letters is to rub a little chalk over the raised letters, and then by means of the ball of the forefinger soften the chalk marks down, when they will be
Photographing Castings and Machinery. 135 found to stand out in bold relief. Other parts which may-require this treatment are the gearing, wheels, springs, nuts, and any fine detail found in the dark portions of the object. It is really wonderful how the teeth of the gearing may be made to show up in the finished photograph, by means of careful preparation with a little powdered chalk.
Study The Subject Carefully. One should always look over the object being photographed very carefully before making the exposure, and see that all detail within range of the lens is perfectly distinct, and that it will reproduce properly. In cases where outlines of portions of a tool or a machine are backed up with other dark parts, and therefore do not appear with enough contrast, much may be done by chalking the edges so that they appear with a light line against a dark background. The chalk when properly applied gives a slate color to the parts to which it is applied, thus rendering them a more neutral tone, which photographs with detail.
Preparing Rough Castings. Very often it will be necessary to photograph rough castings before they have received their finishing touches. The manner of procedure differs materially from that of completely finished machinery. These castings are frequently of great weight, and, varying in their shape and dimensions, are likely to appear rough and spotted. They are generally photographed without any painting. In this condition they appear somewhat patchy and show an abundance of chisel marks from the hands of the dressers. These marks will probably present a bright, shiny appearance when viewed at certain angles of lighting, and these parts will appear quite unlike the dull gray of the remaining piece.
217. Then again, there will be other portions where large patches of dark-colored metal will almost be sure to be present. The best way to prepare the surface of castings is to forcibly throw moulder's sand on the surface or dust it on. In all dressing shops there will be no want of this material, as the castings are usually literally surrounded with sand. After the dry sand is forcibly thrown upon the parts the surface should be gently dusted over with a little dry waste. The bright, glaring chisel marks will have disappeared and the large dark metallic patches will be as gray as the rest of the piece.
218. In all rough castings, even at the stage where they leave the dresser's hands, there will be small holes or indents on the surface, which appear in exaggerated form under side lighting. It is always advisable to doctor the more pronounced of these before exposing the plate. The best material to use is moulder's putty, which when first applied to fill up these little holes will appear as dark dots against the light gray color of the casting, but a handful of dry moulder's sand thrown forcibly on them will make the dark spots vanish.