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. Long soaking in the bath and wash waters very materially affects the brilliancy of the prints. Because of this, one cannot be too particular about the speed of various baths, and the constant handling of prints in the different wash waters to thoroughly remove chemicals which might tend to retard the action of subsequent baths, or to endanger the permanency of the resulting print.
Practice Work. The manipulation of platino or any matte surface printing-out paper is exceedingly interesting, for with this product, more than any other, you can retain and reproduce accurately, every quality in the negative. As no product will give more beautiful halt tones than this paper, the manipulation of it becomes most interesting and fascinating, as a great variety of effects may be obtained with proper handling. As matte prints require much deeper printing, most failures lie in this department. Therefore, for your practice work, make several prints from different negatives. Number each print before toning and mark them in some way so you will know the depth to which each particular print was printed, remembering that with soft negatives you carry the printing farther than for strong ones. In the toning observe the action of the gold bath on the first print. When the print first enters, does it tone smoothly, or does it bleach? Note this data on the back of the print. If the bath is altered in any way, note the action of the second test print. Use a soft pencil when writing remarks on the back of the prints. It is well to abbreviate as much as possible, making only necessary notes while prints are wet. Never use an indelible pencil for this work.
208. After the gold bath is working properly, note the color of the different prints toned in this bath. This is important, as the final color of prints is controlled in the gold bath. Observe the speed of the gold bath. Next, watch the action of the platinum bath. It is a good plan to remove some of the prints from the gold bath at different stages of color, that is, tone some deeper than others. Observe the effect of each in the platinum bath. When all are toned you will, undoubtedly, have a variety of colors. Do not allow this to discourage you, however, as here is where you gain experience.
209. Before fixing, note on a sheet of paper, or memorandum book, the number of each test print that you have toned. Make a record of the appearance of each print in the printing, how it acted in the gold bath, and the color of the print when removed from the gold bath and the color of the print when it came from the platinum bath. Make such notes as described above on several of your most important test prints. This data will prove vitally important for future reference. Next, before placing prints in the hypo, run them through the sulphite of soda bath as instructed. In this bath will be found the means to cover a multitude of failures. Prints in this bath will all darken and become one color; so they will enter the fixing bath at an even tone, the results being uniform prints. Some of the prints, however, will be more brilliant than others, but with notes attached to the test prints, and filed in the proof file, you will have most excellent data for future guidance.
Note. - In localities where very alkaline water is used some difficulty may be experienced in obtaining brilliant prints by using part old and part fresh toning bath. Under such conditions it would be advisable to prepare a fresh bath for each batch of prints, allowing the bath to stand for a few hours, to ripen, before using.