Right at the outset, let me give enormous credit and thanks to Denise Ross, whose wonderful website, http://www.thelightfarm.com/, gives the most comprehensive and well written compendium of existing knowledge and carefully reported results from the world of still photography emulsion making that's out there. She's amazing, and sets a standard for openness and systematic work. Thanks, Denise!
As I starting point, I'll be using a slightly modified version of a recipe from Denise Ross, published on her website here:
HMFI Camera Emulsion starting point
Start by making the necessary stock solutions (1% KI). Then, make up these three solutions:
Solution A: Salted Gelatin
Soak the gelatin in the water for about 30 minutes. Meanwhile, dissolve together in a separate small beaker:
|Distilled Water||13ml||room temp (~20°C)|
|Potassium Iodide, 1% Solution||0.75ml*|
- The original recipe calls for 15 drops, but in the interest of repeatability I substitute ml according to the official metric definition of 1 drop = .05ml
Add this salt solution to the gelatin solution.
With slow stirring, heat the salted gelatin in the 41°C waterbath for 1/2 hour.
Solution B: Ammoniacal Silver
|Ammonium hydroxide, 28-29%||~5.5ml|
The key to this solution is all in the mixing procedure! MAKE SURE YOU HAVE AN EXHAUST FAN OR REALLY GOOD VENTILATION BEFORE ATTEMPTING THIS! The concentrated Ammonia called for is NOT something you want to be around, and potentially injurious to breath!
Thoroughly dissolve the silver nitrate in the water. Under ventilation, with a dropper add the ammonium hydroxide slowly with stirring (Add a little. Stir about 15 seconds. Repeat.) A brownish-black silver hydroxide precipitate will form almost immediately. Continue to add and stir until the solution starts to clear a bit. Slow down the addition rate to a drop at a time and stir longer between additions. When you think all the little black flecks have dissolved, add one more drop of ammonia and stir thoroughly. It is important to avoid excess ammonia. The total amount of added ammonia should be very close to 6 ml.
Fill a closed stopcock buret staged to be ready to move into position over the beaker of salted gelatin.
Solution C: Plain Gelatin