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.
Sensitizing Bath Dish. The sensitizing bath dish used has a flat bottom and is usually made of papier-mache 20 x 24 inches in size, or large enough to receive a full-size sheet of albumen paper. These trays are also supplied in smaller sizes, known as half-sheet size trays; but, they are not so convenient as the paper must be cut in halves before sensitizing, and this not only requires more work, but also necessitates the extra handling of the paper, which sometimes is injurious.
Glass Rod. The glass rod is a round tube about 5/8 inches in diameter, being about 24 inches long and flat on both ends. This rod is laid over one end of the tray and attached fast on each end with rubber bands. The bands are slipped through screw-eyes screwed into the table, one on each side of the end of the dish and looped over each end of the rod. The object of the rod is to supply a smooth surface over which the paper may be drawn when taken from the bath, thus removing all surplus solution from the surface of the paper.
Sensitizing The Paper. The sensitizing of the paper should be done in a room free from direct light, and the room should be perfectly clean and free from dust. It is a good plan, where the floor of the room is of rough boards, to sprinkle the floor lightly a half hour before you begin sensitizing the paper. A table from 6 to 8 feet in length should be provided. The sensitizing dish should be arranged in the center of the table. On the one side of the dish place your albumen paper; the other side reserve exclusively for clean blotters, which can be used continually for months.
16. To begin sensitizing, first filter the bath into the sensitizing tray. This can easily be done by suspending a large glass funnel over the bath dish. In the neck of the funnel place some absorbent cotton. The cotton should have been previously dipped in pure water. Where a special funnel is used for this purpose only, the same cotton can remain in the funnel until it becomes charged with sediment and dirt; it will not need to be wet after the first time used.
17. A simple way of suspending the funnel, where no special rack is provided, is to take an ordinary studio head-rest and adjust the height so the ears of the stand hang over the bath dish at a height of about 10 inches. Place the funnel between the ears of the stand, which will hold it from tipping. Pour the silver solution into the funnel and filter sufficient of it to give you a bath which will fill the tray to a depth of at least half an inch.
Skimming The Bath. Sometimes you will find a fine scum collected over the surface of the bath, even after filtering. Just before beginning to sensitize, float a sheet of tissue-paper over the bath. This will take on all the scum and your bath will be perfectly clean.
Rubbing The Albumen Paper. Before floating the paper on the bath, first with a handful of absorbent cotton, rub the the cotton freely, but not heavily, over the surface of the sheet of albumen paper. Do not allow the fingers to touch the paper, as they will leave marks and lines on it. The rubbing of the cotton over the paper has an electrifying effect on the surface so that the albumen will take on the silver more evenly.