This section is from the "Henley's Twentieth Century Formulas Recipes Processes" encyclopedia, by Norman W. Henley and others.
Whiten the negative in the saturated solution of mercuric chloride, wash and -blacken with a solution of sulphite of sodium, 1 in 5. Wash well.
The reduction is perfect, with a positive black tone.
Dissolve 1 drachm of bichloride of mercury in 7 ounces of water and 3 drachms of iodide of potassium in 3 ounces of water, and pour the iodide solution into the mercury till the red precipitate formed is completely dissolved.
For use, dilute with water, flow over the negative till the proper density* is reached, and wash, when the deposit will turn yellow. Remove the yellow color by flowing a 5 per cent solution of hypo over the plate, and give it the final washing.
One part of agfa solution in 9 parts water (10 per cent solution). Immerse negative from 4 to 6 minutes.
Dissolve 1 part of iodine and 2 parts of potassium iodide in 10 parts of water. When required for use, dilute 1 part of this solution with 100 parts of water. Wash the negative well and place in this bath, allowing it to remain until it has become entirely yellow, and the image appears purely dark yellow on a light-yellow ground. The negative should then be washed in water until the latter runs off clearly, when it is floated with the following solution until the whole of the image has become uniformly brown:
Schlippe's salt....... 60 grains
Water..... ......... 1 ounce
Caustic soda solution,
10 per cent........ 6 drops
Finally the negative is again thoroughly washed and dried. The addition of the small quantity of caustic soda is to prevent surface crystallization. It is claimed that with this intensifier the ] operation may be carried out to a greater extent than with bichloride of mercury; that it gives clear shadows, and that it possesses the special advantage of removing entirely any yellow stain the negative may have acquired during development and fixing. Furthermore, with this intensifying method it is not necessary to wash the negative, even after fixing, as carefully as in the case of the intensifying processes with mercury, because small traces of hypo which may have been left in the film will be rendered innocuous by the free iodine. The iodine solution may be employed repeatedly if its strength is kept up by the addition of concentrated stock solution.
Potassium ferricyanide (washed)..... 48 grains
Uranium nitrate..... 48 grains
Sodium acetate...... 48 grains
Glacial acetic acid.... 1 ounce Distilled water to.. .. 10 ounces. Label: Poison. Immerse the well-washed negative till the desired intensification is reached, rinse for 5 minutes and dry. This intensifier acts very strongly and should not therefore be allowed to act too long.