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.
Strengthening The Sensitizing Solution. The amount of nitrate of silver to be added to the bath if it proves too weak, or the extra amount of water to add if it is too strong, can be very easily calculated. First, ascertain the number of ounces of solution, and multiply this by the number of grains strength per ounce. For example: If the argentometer test shows a strength of 52 grains per ounce and you desire to strengthen it to 60 grains, and the total amount of solution is 20 ounces, multiply the number of ounces (20) by the number of grains (52), which gives 1040. In order that your bath tests 60 grains per ounce, you must have 1200 grains of silver in the 20 ounces of solution. Subtract 1040 from 1200; which is 160. This will be the number of grains which must be added.
Preserving The Sensitized Paper. It is always advisable to use the paper as freshly sensitized as possible. The paper sensitized in the morning should be used that same day. In warm weather the paper will take on quite a yellow tint on the second day. At times, however, the morning may seem fair and a great deal of paper be prepared. By nine o'clock the sky becomes overcast and settles in for a rainy day. Fuming the paper will enhance its keeping quality, and it is advisable, under the above conditions, to fume it for a second time and then place it under pressure in a light-tight drawer.
Caution. The photographer will find that the change of seasons may make it necessary for him to change the strength of the bath, and also necessitate going to some extra trouble in order to obtain brilliant prints, sensitizing the paper so that it will not print mealy and that there will be no tear drops.
47. The first change necessary will be in the fall of the year, when the weather is colder; then you must increase the strength of your silver bath and also float your paper longer. It may be necessary, in order to avoid these tear drops, to rub the paper more thoroughly with the cotton, just before you float the paper on the bath. This rubbing warms up the albumen and causes it to take up the silver bath more freely. If the prints are mealy, it is probably because your bath is becoming filled with organic matter or it has turned slightly acid. Carefully test your bath and, if necessary, give it a sun bath. This is fully explained under the heading "Keeping Bath in Working Condition," Paragraph 40.
48. In the spring of the year you will meet with the same difficulties. You should apply the same remedies, with the exception that in the warmer weather the strength of the bath may be slightly decreased, and the paper should not be floated quite so long.
Difficulties. - Sec Chapter III (How To Proceed), Paragraphs 74-S5.