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.
Introducing Clouds Into Slides By Contact. Either of the preceding methods described for combining clouds with landscapes in slides is applicable to the making of slides by contact as well as by the reduction method. The same principles hold good in both cases.
Cover-Glass Method By Contact. The landscape slide should be exposed, the sky portion, of course, being held back entirely, so that when developed the sky of the slide will be perfectly clear glass. Now, place (preferably) a 4 x 5 cloud negative in a printing-frame, and adjust the landscape slide, with its back (the glass side) next to the film of the cloud negative, so the clouds will come in proper position. Carefully observe the location of the landscape slide. Replace the landscape slide with a lantern-slide plate. Insert the back of the printing-frame and expose as usual but at a farther distance from the light. During the exposure shade the foreground or landscape portion, so there will be no impression made on this section.
946. Another method of securing the cloud slide is to adjust the landscape slide on the cloud negative, and then on top of this place the sensitive lantern-slide plate. Insert and fasten the back in the frame. If there should be any transparent spots in the landscape, these should be covered with opaque paper. Make the exposure in the usual manner. On development it will be found that the landscape slide has acted as a mask, and that the clouds appear in proper position on the lantern-slide plate.
947. After both negatives are dry they should be bound together. If, for any reason, the lower part of the cloud slide is affected by the light, this portion should be reduced with Ferricyanide. In other words, the landscape part of the cloud slide should be clear glass and the sky part of the landscape slide should also be clear glass. Then, on bringing the two together a brilliant combination cloud and landscape slide will be obtained.
Cloud And Landscape On Same Slide By Contact. If it is desired to print the cloud and landscape portions on one slide, place the landscape negative in the printing-frame, first having made a mask as previously described. Expose the landscape portion, holding back the sky by using the mask. Now, remove the landscape negative and insert the cloud negative, placing the slide in proper position, which position should have been ascertained before starting to print. When making the exposure of the cloud portion, the landscape part of the sky should be protected from the light by using the mask. With a little experience it will be possible to give uniform exposures and secure excellent results by this latter method; although, as is the case in making slides by reduction, the beginner will meet with better results if he employs the "cover-glass" method. Should the landscape or the sky part of the combination slide be too dark, its density may be reduced by using a Ferricyanide reducer.