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.
Mercury Solution Can Be Used Repeatedly Without Renewing. The mercury, or in other words Solution No. 1, can be used repeatedly. The solution used, however, should not be placed back in the bottle of stock solution, but should be poured into a separate bottle, and labeled "Intensifier ready for use." Should this bath by constant use become weak and work slowly, add to it a little of the fresh stock solution, thereby keeping the bath always in good working order.
Clearing Solution Can Be Used Repeatedly Without Renewing. The clearing solution, or sulphite of soda, can be used a number of times, as long as it will clear the plate by changing the color from white to original color. Just as soon as the action becomes slow it is advisable to discard it, and make a fresh bath.
Special Formula For Strengthening Negatives Of Uncertain Fixing. Another formula which we recommend in case there is any doubt in your mind as to whether the negative has been properly washed and freed of hypo, is as follows:-
Bichloride of Mercury...................
149. Add to this 150 grains potassium iodide, or enough to nearly dissolve the red precipitate first formed. Next add 120 grains of hypo - sulphite of soda in crystals, or sixty grains granular. In this solution immerse your plate until sufficient density is obtained. Examine the plate by looking through it, just as you would when using the single bichloride of mercury intensifier.
Fixing The Plate. After the plate has taken on as much strength as you desire, place it in a very weak hypo - sulphite of soda fixing bath, hydrometer test ten degrees, for about fifteen seconds, after which wash thoroughly, and set up to dry. The image on the negative will then consist of a double iodide of silver and mercury of a reddish brown color, with good printing qualities. This latter formula is only recommended where there is any doubt as to whether plates are thoroughly fixed. In order to avoid using the last mentioned bath, and to be certain that the silver is entirely removed from the plate, it is advisable, after developing, to always fix a plate at least fifteen minutes after the silver has disappeared; then if you thoroughly wash, plates so treated can be intensified with the first formula given, which is most simple.
Removing Varnish From Plates To Be Intensified. There are times when a negative has been varnished for retouching, or for preserving the surface, which you afterwards decide should have been intensified. To intensify such a plate it is first necessary to remove the varnish. This you can do by soaking the plate in wood alcohol, and then with a tuft of absorbent cotton which has been thoroughly saturated with the alcohol, gently rub off the varnish, after which the negative should be placed in clear water to soak for about twenty minutes, when it will be ready for intensifying.
Removing Varnish With Turpentine. Another method of removing varnish or retouching fluid, as well as the lead, from a plate, is to apply turpentine with a tuft of cotton. After the varnish is all removed rub the plate dry with a little dry cotton, and then soak in clear water for twenty minutes, after which apply the mercury.
Plates To Use For Experimenting. It is advisable, in preparing this instruction, to make use of some discarded, thin, weak negatives for your first experiments, and intensify according to the formula given. After you become familiar with the effect of the chemicals applied, you can then use a plate which you desire to save and improve for future printing, and apply the intensifier to this plate.
154. In preparing results of this instruction one should make good proof prints before and after intensifying, and all data pertaining to the method of intensifying the plate should be recorded on the back of the proof, always dating each proof and numbering whether first, second or third experiment. These proofs should be filed in your proof file for future reference, as they will be your guide in future experiments.