Van dyke brown
Encyclopedia
Van Dyke Brown is an early photographic printing process. The process was so named due to the similarity of the print color to that of a brown oil paint named for Flemish painter Van Dyck.

Printing

Printing with Van Dyke Brown requires the use of a large format negative in the size of the desired print, a suitable substrate for coating and subsequent printing, and a UV light source, either sunlight or suitable bulbs.
The substrate can be almost anything that the solution will adhere to. Watercolor paper is a good first choice, but trickier substrates such as metal, glass or tile can be first 'sized' with gelatin or arrowroot to facilitate coating. The substrate is coated with solution under tungsten light, air dried, and coated a second time if desired for a stronger image.

The negative is placed on the thoroughly dried coated substrate, and is then weighted with a piece of glass. Frequent printers often use a printing frame to ease the checking of printing progress without disturbing the registration, or alignment, of the negative on the paper. These printing frames also ease the printing of a second coat over the same image.

The glass-negative-substrate 'sandwich' is exposed to a source of UV light. UV bulbs offer more control and consistency of light than sunlight, but at greatly increased cost. Standard daylight fluorescents produce some UV light, but printing times may be very long. A good starting point for printing time is to check a region of your photo that is very light but should still show some tone or detail (a highlight), and note how long it takes to register this detail, and print as long again. The latent image now appears, although flat and lacking substantial shadow tones.

Processing the printed image

The image must now be washed, or cleared, in several changes of water to remove soluble iron and silver compounds. It is good practice to slightly acidify the wash water, as iron compounds are more soluble in acid. A pinch of citric acid, dab of vinegar or pineapple juice will do the trick. As the image soaks, white cloudy precipitate of silver chloride will appear from the reaction of silver nitrate
Silver nitrate
Silver nitrate is an inorganic compound with chemical formula . This compound is a versatile precursor to many other silver compounds, such as those used in photography. It is far less sensitive to light than the halides...

 with chlorine in the water. Continue to wash for a few changes of water after this cloudiness ceases to appear.

Fixing is best done with a weak, alkaline fixer of 5% sodium thiosulfate
Sodium thiosulfate
Sodium thiosulfate , also spelled sodium thiosulphate, is a colorless crystalline compound that is more familiar as the pentahydrate, Na2S2O3•5H2O, an efflorescent, monoclinic crystalline substance also called sodium hyposulfite or “hypo.”...

 with a teaspoon of household ammonia
Ammonia
Ammonia is a compound of nitrogen and hydrogen with the formula . It is a colourless gas with a characteristic pungent odour. Ammonia contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to food and fertilizers. Ammonia, either directly or...

 per liter. The alkali slows the fixing process and prevents rapid bleaching of the image. Almost immediately, the tones of the image will change to a deep chocolate brown. Keep fixing until the whites appear clear; about 2 minutes, and finish with a second, clean fix if desired for thorough removal of salts that would fade the image. Use a fixer clearing bath of sodium sulfite
Sodium sulfite
Sodium sulfite is a soluble sodium salt of sulfurous acid. It is a product of sulfur dioxide scrubbing, a part of the flue gas desulfurization process...

 to help remove residual fixer, and give the print an extended wash fitting the absorbancy of the substrate, around 30-45 minutes for absorbent papers, or 5-10 minutes for gelatin sized tile or glass.

Air dry the print without heat. High heat will change the color of the print to more neutral and weaken the shadows.

Chemistry

Observe precautions for handling chemistry. Know your tools. Wear gloves and goggles if in doubt.

Like many photo processes, VDB is based on the light sensitivity of a salt, silver tartrate, which gives it a unique color and scale.

Formula

  • Part A:
    • 33 ml Distilled water
    • 9 grams ammonium ferric citrate
      Ammonium ferric citrate
      Ammonium ferric citrate is a food additive with E number E381 used as an acidity regulator. It is a green or reddish-brown powder which is very soluble in water....

       green OR substitute
    • 18 grams ammonium ferric citrate brown
  • Part B:
    • 33 ml distilled water
    • 1.5 grams Tartaric Acid
      Tartaric acid
      Tartaric acid is a white crystalline diprotic organic acid. It occurs naturally in many plants, particularly grapes, bananas, and tamarinds; is commonly combined with baking soda to function as a leavening agent in recipes, and is one of the main acids found in wine. It is added to other foods to...

  • Part C:
    • 33 ml Distilled water
    • 3.8 grams Silver nitrate
      Silver nitrate
      Silver nitrate is an inorganic compound with chemical formula . This compound is a versatile precursor to many other silver compounds, such as those used in photography. It is far less sensitive to light than the halides...



Silver nitrate can burn and causes VERY permanent brown stains on almost everything it touches. Stains won't be evident until exposed to UV light. Use caution.

Add part B to part A, and slowly add part C while stirring. Store solution in darkness in a tightly lidded glass bottle and age for a week. Solution keeps stable activity for years after ripening period.
The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
x
OK