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.
Embossing Print. When prints are dry, in order to produce the plate-sunk effect, place them face down on the paper guide of the embossing device. Adjust the print to the opening of the guide, always allowing more space at the bottom than at the top of the print. When in proper position close the embosser and turn it face side down, embossing the print by rolling the back with an ordinary rolling pin, or it can be done by pressing around the edges of the opening with a smooth tube like the bottom of a spoon, or even an oval shaped glass paper weight. Anything smooth that will not rub the print will answer for the purpose. After the print is embossed it should be properly engrossed with the name of the photographer. Usually a lead pencil is employed and the name is written in a counter-sunk corner.
Enclosures. Collodio carbon prints should always be enclosed in a flexible enclosure, style of which can be selected according to the taste of the artist or customer. Suitable folders in many styles and sizes are kept in stock by regular supply houses. As the material for the folders is supplied by the manufacturers in various grades and colors, the photographer can make them and supply customers with folders entirely original.
General Notes On The Manipulation Of Collodio Carbon Paper. In drying collodio carbon prints it is necessary to change blotters quite frequently, always using dry blotters each time. If allowed to lie in the blotters in a damp condition, bleached or mildew spots are liable to occur. After the surface is comparatively dry they may be transferred to fresh blotters, or cardboard, as directed, and left undisturbed for 10 to 12 hours. Or, it will do no harm to allow them to remain in the cardboard blotters over night. The prints should be examined before removing them from the cardboard permanently. If removed before entirely dry they would curl somewhat, so the cardboard and blotters should again be changed and the prints allowed to remain in the fresh dry cardboard and blotters until bone dry. If the prints, being removed from the cardboard slightly damp, are inclined to curl, they may be flattened by moistening the back with a damp sponge, returning them to the dry blotters and cardboard, placing them under a little pressure and allowing them to remain until bone dry.
370. Should prints show a tendency to blister in the hypo or final washing, transfer them, after fixing, to a plain salt water bath composed of water 64 ounces and salt 4 ounces. While blisters are more likely to appear in warm weather, it is still a wise precaution to always use this bath with collodio carbon paper and thus avoid this difficulty.
Practice Work. As the chemical manipulation of collodio carbon paper is very similar to platino or other matte surface papers, the advantage of this product lies in the fact that collodio carbon paper is coated on a heavy stock and should, when finished, be similar to matte surface paper which has been backed. With collodio carbon paper there is no necessity for mounting as the prints lay flat, but the paper should be printed with wide margins and also be embossed. In printing collodio carbon paper, of course, the negative must be blocked, and a larger printing frame than the size of the original negative should be employed. The opening over the negative may be oval or square, in fact any shape to suit the negative used. Select a few of your choice negatives and make a few prints. Use paper large enough to give a liberal white margin and after the prints are toned and dried, prepare an embossing device to suit the size opening of the picture you are printing. Emboss the print and engross with your signature. It is then complete. Your first efforts should be filed in the proof file for future reference.