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.
Caution. In preparing the backing paper it must be understood that the emulsion on this paper contains preserving chemicals which it is necessary to remove before using. The paper should, therefore, be washed in four changes of water - about five minutes to each change. To the second wash water add one ounce of saturated solution of carbonate of soda to every gallon of water used. Then in order to have this paper as thoroughly wet as the prints are when they are squeegeed to the backing paper, it should be allowed to soak during the toning and washing of the prints.
228. In cutting the backing paper care should be taken to see that the grain of the paper in backing runs the same way in the sheets as the grain of the paper in the print. This you can ascertain by cutting off a piece, say two or three inches, and placing in a tray of water. If it curls up at the side, the grain runs the wrong way; if it curls up at the end, the grain runs crosswise. Always see that the prints and the backing curl in the same way of the sheet. This is necessary in order to insure the prints lying flat, but if the grain of the backing paper does not run the same as the grain in the print the finished print would curl slightly.
229. All surplus water on the margin of the glass around the edges of the prints must be carefully absorbed with a blotter before mounting the backing paper to it. A drop of water carelessly left on the glass would interfere with the adhesion and cause the prints to cockle at that point. Prints should be allowed to dry slowly at first until the paste is thoroughly set, or until they are about half dry; then the drying may be hastened by artificial heat. If you find any trouble with the prints sticking to the glass - this may happen when mounting six prints at a time - take a piece of pure castile soap and swish it through the water a few times until the water feels somewhat slippery, or smooth to touch. Place the prints in this soapy water just before you are going to place them on the glass. Prints treated in this way will readily come from the squeegee glass.
Practice Work. Toning with Aristo gold and platinum prepared solutions is performed in exactly the same manner as where you prepare your own stock solution. However, for practice work follow the same method as given in the previous instruction for printing and toning matte surface papers, making notes accordingly and filing the test prints in your proof file. Always date each print and note the bath used.
231. Platino prints when backed will always lay flat and it is advisable that they be printed with a margin. At any rate they should be glazed on glass, and when so glazed the finished print gives a very smooth, even texture, the exact quality of the negative being truly reproduced in the print.
YOKOHAMA HARBOR Study No. 10 See Page 386 By Wm. II. Phillips.
PORTRAIT Study No. ii By Rudolf Eickemeyer.