The Van Dyke process is one of the most basic of all the silver salt emulsions. Its characteristics are very similar to blueprint emulsion in that it has a very favorable continuous tone response, it is easily applicable to a variety of surfaces, is highly stable, etc. Moreover, it produces a very photographically pleasing deep brown color. Like the three other silver salts used in photography (silver chloride, silver iodide, silver bromide), silver nitrate becomes light sensitive when placed in the presence of organic substances. Although not as sensitive generally as the other salts, the silver nitrate emulsion is easier to prepare and process.
NOTE: Silver nitrate is highly poisonous, can be used in making explosives (which can sometimes make it difficult to obtain except institutionally), and leaves dark brown stains on the skin for many days; therefore treat it with care and wear gloves.
Mixing: Dissolve each of the chemicals separately in 250 cc of water. Mix the Ferric Ammonium Citrate and Tartaric Acid solutions well together. While continually stirring, slowly add the Silver Nitrate solution, and continue stirring until well mixed. Finally, add remaining 250 cc of Distilled Water, and stir again well. Keep the resulting solution in a dark brown bottle away from direct light. Under such conditions the mixed solution should keep in good condition for several months. The solution should be allowed to "age" for two or three days before use. It should be stirred or shaken before and periodically during use.
Application: The paper or fabric an be dipped in or floated on the solution, but probably you will want to brush or swab it on. Treat the Van Dyke emulsion as blueprint emulsion: it needs to saturate the fibers of the ground. Coat evenly and if coating cloth, the emulsion must be worked well into the fabric. However, be as frugal as possible because Silver Nitrate retails for about $12 an ounce. Also, because you are working with silver, the coating should be done on acid-free, high or pure rag content paper (BFK seems to be the best), or on natural (e.g. cotton) and acid free cloth (achieved by pre-washing). Contact between Silver Nitrate and acid often results in mottling and fading.
Exposure: After drying, contact print under strong actinic light:
Again, cloth or other low-reflectance material needs about 50% more exposure.
Development: (OPTIONAL: Immerse the print for about three minutes in a solution of 100 grams Borax (not too critical - about two teaspoons is fine) per 1 liter (or quart) of water.)
Wash in running water for five to ten minutes. This will produce an image of a somewhat disagreeable yellowish color, but it will intensify and change to a more pleasing brown if left at this point to dry.
Fixing to Arrive at Van Dyke Brown: If preferred, after the washing (or development in the Borax solution), the print can be immersed for 1-2 minutes in a plain hypo solution of 50 grams (one teaspoon-full) per 1 liter/quart of water. This will change the image color to a very agreeable Van Dyke Brown, as well as making the emulsion more stable. Fixed prints need to be finally washed for ten minutes in running water before drying.
NOTE: Because blueprint and Van Dyke contain opposing substances (Silver Nitrate vs. Potassium Ferricyanide), they tend to attack, neutralize, or obliterate each other when used on the same ground. This can produce very interesting and beautiful results which get away from the mechanicalness of the traditional process.
The Kallitype process is another using Silver Nitrate, and although it is more complicated than the Van Dyke process, it provides better control of the image coloration.
Mixing: Dissolve 150 grams of Ferric Oxalate and 10 grams of Oxalic Acid in 1000 cc Water at 100 degrees F. Filter several times through three layers of muslin. Add 60 grams of Silver Nitrate slowly while stirring, and continue stirring until completely dissolved. Keep in dark brown bottle and allow to age three days before using.
Apply to acid-free ground as with Van Dyke process.
Expose as with Van Dyke process.
Development:Immerse print for 15 minutes in a solution of 90 grams of Borax, 60 grams Rochelle Salts, and 1000 cc water. This should produce a black image. To increase the image contrast, add 1 to 3 cc of a 10% solution of ammonium dichromate to the developing solution. To produce purplish-brown image coloration, change the proportion of the developer to 45 grams of Borax and 90 grams Rochelle Salts. For a sepia tonality, omit the Borax and 90 grams Rochelle Salts. For very rich black coloration (but not as great stability), over-expose the print by 50% and mix and use a developer of 120 grams of Sodium Acetate and 1000 cc water.
Clearing and Fixing: After development, rinse print briefly, and then clear in a solution of 120 grams Potassium Oxalate in 1000 cc water for several minutes. Fix for 5 minutes in a solution of 45 grams Sodium Thiosulfite, 12 cc Household Ammonia, and 1000 cc water. After fixing wash the print in hypo clearing agent for 2 to 3 minutes and running water for 10 minutes.