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.
Blocking The Negative. Generally commercial photographs require white backgrounds. This effect can easily be obtained in the following manner: Sew together a couple of widths of white muslin, the length required to completely shut out all objects back of the subject to be photographed. Attach a pole to each end of this screen. The poles serve as standards for stretching the muslin, and also to roll it on when not in use.
247. When preparing the object to be photographed, stretch the screen behind the object, when sufficient white ground will be obtained to give a good, clear outline. Sometimes, where the sheet requires a good, strong light, by keeping the sheet moving during the exposure a sufficient white ground will be produced for all practical purposes, but for very large work, in order to produce a pure white effect you must resort to what is called blocking-out. This you do upon the negative.
248. Before blocking the negative, all alterations - such as reducing strong high-lights, building up weak parts, etc., thus equalizing the tonal values - should be made in advance of blocking the negative. By reference to Fig. A, Illustration No. 55, you will observe that the top of the machine is in very strong high-light. This was unavoidable, as you will find in many instances where such work is to be photographed, for all the illumination comes from the skylight directly overhead. In making the exposure enough time was given the plate to fully expose the densest shadows, and the plate was then developed by the regular method of development and afterward locally reduced with a weak solution of red prussiate of potash. Finally, the background was blocked out, with the results as they appear in Fig. B.
249. The first step in blocking the negative is to outline the subject, and this is best done by applying, to the film side of the negative, liquid opaque, gamboge or Strauss Marl, or any opaque substance which will not stain the print. With a small brush charged with the opaque, trace the outline carefully, and when the outline is complete fill in and paint over all parts you wish to appear white in the print. In order that the opaque may take to the film readily, carefully wet a portion of the plate. Do this by swabbing it, only once, with a tuft of wet cotton. This will not wet the film sufficiently to injure it and the opaque will adhere to the film much easier. Should you, by accident, apply the opaque to parts not wanted, the surplus so applied can be removed with a tuft of wet cotton.
250. Where the entire background is to be blocked out white, it is best to paint only about one-half inch from the outline, then use yellow post-office paper, or any black opaque paper, for masking out the remaining background. The mask should be cut so as to lap over the opaque. Outline sufficiently with the opaque, however, to give a clean white background. Any openings in the object, or any open work, should also be blocked with the opaque in the same manner as the exterior portions.
251. Fig. A of Illustration No. 55, is a reproduction from a negative made of a metal turning lathe before being blocked, while Fig. B shows the method of blocking out and accentuating various portions.
Another Method Of Blocking. A very satisfactory method to employ in blocking out machinery and in working up detail is to make an enlargement on bromide paper, of the original negative, and then with white ink outline the subject and block out the background on the print. By employing this method it will be possible to darken or lighten any portions desired, or to build up letters and other detail. When the enlargement has been worked up to one's satisfaction, a copy of it can be made to what-
Illustration No. 56 Commercial Photographic Subjects
Illustration No. 45
Bed Brace for Camera
See Paragraph 180
Illustration No. 57
Commercial Photograph - Stove
See Paragraph 258 ever size is desired, and then prints made from the final negative. Where this method is preferred, a small camera may be employed, say a 5 x 7 or 8 x 10, and the enlargement made from the small plate. After the enlarged print is worked up, any size plate desired may be used for reproducing it, and contact prints made in the regular way.
253. A number of commercial subjects which have been photographed and the majority of them blocked out in the negative, are shown in Illustration No. 56. The original prints having been made from 10 x 12 to 18 x 22 plates, they naturally have suffered considerably by the reduction, yet they serve to illustrate the way such work is handled in the blocking out of the background.