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.
Sepia Tones Produced With Bichloride Of Mercury. Still another toning bath is called "mercury toning." While we do not recommend mercury toning on account of lack of permanency - the prints generally returning to the black tone in time - yet some very beautiful effects can be produced, using bichloride of mercury as the toning agent. You must be cautious never to use mercury toning trays for other purposes. If you do an endless amount of trouble will be met with. Should the least particle of mercury be carried to any trays used for black platinum prints you would have trouble with all kinds of spots. For this reason when using mercury do so with the utmost care. Keep the solutions and trays isolated from other work.
Mercury Sepia Developing And Toning Bath.
Bichloride of Mercury C. P...............................
635. Place in a 10-oz. bottle and label it "Mercury Solution." Also mark in strong black letters "POISON," as taken internally its effect is deadly. To 50 ounces of regular platinum developer, used for black tones, add one ounce of this mercury stock solution.
Toning. Print exactly the same as for black tones, develop the print in the mercury developer until the desired tone has been reached and then place in the acid clearing bath made one-third as strong as for black tones. After fixing, wash thoroughly and dry in the usual manner. If tones secured by this bath are not as warm as desired, the addition of more mercury will result in warmer effects.
637. As before stated, we do not recommend the two latter methods for obtaining sepia tones. We have given this formula for the benefit of those who like the effects which can be produced by this method. But, for good, permanent, even tones, the regular prepared sepia papers are the best.
Practice Work. For first experiments with sepia prints on platinum paper, prepare the bath ready for use, before making prints. Judging the print for sepia is similar to judging for black, except that the printing is not carried quite so deep for the sepia, as it dries from one to two shades darker when finished.
639. It is advisable to make but one print at a time, developing each immediately after printing, and observing carefully the gradation. Allow the image to fully develop. If not over-printed it will not be too dark. It is not advisable to make more than two or three prints, before drying. Note how they dry before making more prints. Your first efforts will serve as a guide for future work. In all cases, for experimental purposes with platinum paper, it is advisable to use the medium rough grade of paper. You can better judge results with this grade than with either of the extremes - extra rough or very smooth.
640. Should you experience trouble in the manipulation, refer to the difficulty department. Read carefully and you will surely find the cause, prevention and remedy for the trouble. Preserve first efforts, whether good or bad, because it is really an advantage to meet with some failure at the start, as you then have an invaluable guide for future endeavors. In any event, make careful notes on all test prints and file them in the proof file for future reference.