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.
Printing-In Figures In Groups. When it is desirable to add an extra figure to a group, a small negative must be made of the additional figure, the size and position to be in keeping with that of the group. If a copied picture is to be added in place of an original sitting, you must be guided entirely by the style of copy and the arrangement of the original group, providing space for the additional figure accordingly. With the single figure copied, block the negative. Next place the group negative in a printing frame, covering it with a sheet of sensitized paper. Hold the negative in the frame before the light, and with a lead pencil outline on the back of this paper the space to be occupied by the additional figure. Next provide yourself with a printing frame a size larger than the group negative. Place in this frame a heavy glass. On this glass place the single negative covering it with the sensitized paper, adjust the figure to the pencil outline on the sheet of paper and then carefully clamp the back on to the printing frame.
1166. The printing frame used should contain a back cover two-thirds of which can be opened so that the small end may be used over the small negative, thus permitting of examination of the print during printing. After the negative and paper are properly adjusted in the frame, mask all of the glass side with opaque paper, admitting only the figure. It is not necessary that the opening in the mask be fitted close to the figure. If the small negative is fully blocked and within half an inch of the figure it will be sufficient.
1167. You are now ready for printing the single figure. Print to the proper depth. When complete remove from the frame, and with a thick solution of gamboge carefully paint over the entire figure. The gamboge must be thick enough to block out all actinic light from the figure. After the gamboge is completely dry, place the group negative in a printing frame, laying the sheet of paper containing the single figure upon the negative, adjusting it to the proper position. This done, clamp the back on the frame and print the remaining group to the same depth that the single figure has been printed. After printing, the gamboge is washed off, the print being toned and finished in the usual way.