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.
The Landscape Slide. For this method the sky in the landscape slide should be represented by perfectly clear glass. If, for any reason, the sky should be a trifle dense, reduce it or clear it away by the application of Ferri-cyanide reducer, applied with a small tuft of cotton. In making the landscape slide see that the sky part of the negative is perfectly opaque; then the slide will be represented by absolutely pure glass. The slide should be washed and dried in the usual manner.
Cloud Slide. To make the cloud portion, take another lantern-plate, and, having selected a suitable cloud negative, make a lantern-slide of this. A cloud negative should be adjusted in the camera, so as to occupy the position on the plate that will enable it to register in the clear portion of the landscape slide. This may be accomplished by holding the landscape slide over the image of the cloud negative shown on the ground-glass. When proper adjustment has been made of the sky on the ground-glass, proceed to make the exposure and develop the plate.
POLISHING BRASS Study No. 16-See Page 358 Mrs. Myra Albert Wiggins.
Matching Sky With Landscape. Care should be taken to work under the same conditions in making the sky slide as when making the landscape, so that the colors of both may be the same. When the slide has been fixed it should be compared with the landscape portion, to see that the two correspond in density. The sky slide may require a slight intensification, or, on the other hand, it may be a little too dense, necessitating a little reduction.
940. When both of the slides are of equal density place them back to back, with the edges of the slides even. The clouds should not overlap the landscape. If they do, take a tuft of cotton, dipped in Ferricyanide reducer, and, still holding the slides back to back, carefully reduce the part of the sky slide that overlaps the landscape. The reducer should not be used too strong, and care must be taken that none of it reaches the landscape slide by capillary attraction.
941. The two slides should now be dried and bound film to film. This is the best method of obtaining clouds in lantern-slides, and its only drawback is the difficulty which one may experience in being able to get the two slides of exactly the same color when a warm tone is desired. But this slight objection may be overcome by exposing the sky and landscape plates, one after the other, and developing them together.
Sky And Landscape On Same Slide. A method of printing the clouds on the same slide as the landscape, although not quite as certain as the preceding method, is one which will prove very satisfactory to the advanced worker. The cloud negative should, of course, be selected to match the landscape, and a mask then prepared with which to shade the landscape portion during the exposure of the cloud negative. To prepare this mask, take a piece of non-actinic paper, lay it Over the landscape negative, and holding the negative up to a strong light, roughly trace on the paper, with a pencil, the outline of the landscape where it comes against the sky. Cutting along this line will give two masks, one for the sky and the other for the landscape. For convenience the landscape mask may be gummed on a piece of cardboard, but the outline of the landscape should project beyond this cardboard, so it will be a little flexible and not have a thick edge.
943. Place the landscape negative in position, and expose on the lantern-plate in the usual manner. Bear in mind, that the same necessity exists in this method for having the sky appear as clear glass-in order that a brilliant result be obtained-as in the method previously described. Having exposed the landscape negative close the shutter and remove the landscape negative and insert the cloud negative, placing it in the same relative position occupied by the landscape negative. Now expose on the cloud negative about one-third the exposure given the landscape negative, holding the cardboard mask an inch or so in front of the cloud negative, so that it covers that portion corresponding to the landscape in the landscape negative. The mask should be kept moving slightly up and down, so a perfect vignetting and blending of the sky and the landscape is secured. A little practice will soon enable one to place clouds in landscape slides in a very neat manner; yet, for the beginner this method is not as easy as the one first described.