Tuesday, May 20, 2014

The original Caffenol Recipe and Black Caffenol

Caffenol was first introduced by Dr. Scott Williams and the Technical Photographic Chemistry 1995 Class of Imaging and Photographic Technology Department, School of Photographic Arts and Sciences of the Rochester Institute of Technology.

The paper produced about Caffenol can be read here and the original recipe was this one:
Coffee Two (2) Rounded Teaspoons
Baking Soda Two (2) Rounded Teaspoons
Potassium Hydroxide Added to pH 9.0 (approximately One (1) Rounded Teaspoon)
Water 12 oz. or 352 milliliters
Temperature 85 F
Time 25 minutes
Baking soda and Potassium Hydroxide should form a buffer solution to rise the pH of coffee which is acidic and does'nt allow developper to 'penetrate' the film emulsion. The team of Dr. William used also a temperature above 20ºC, 85ºF that is aproximately 30ºC.

The recipe, for simplicity of usage was modified by others, giving the well known recipe that is reproduced at Digital Truth:
Water 8fl oz
Arm & Hammer Washing Soda 2tsp
Folger's Coffee Crystals (not decaf) 4tsp
This last recipe is to be used at 20ºC and takes in average 30 minutes to develop a film.

The problem with this last recipe is that most of the people using it don't control the pH and temperature, the original recipe is more clear and says temperature and pH. And Dr. William was careful not fixing the amount of Potassium Hydroxide but the pH to be reached.

Having this in account, I also proposed to Digital Truth my alternative Black Caffenol to be listed in their collection of recipes, what they accepted after having tested it. Important is to use a pH of 10,4 at 20 ºC, what needs about 5 g of Sodium Carbonate or a little more. The pH is higher than in the original recipe of Dr. William but the temperature is also lower and the time is longer. I think that if temperature is used, the pH and time should decrease too.

No comments: