Tools & Materials
In addition to the standard darkroom paraphernalia, including a scale, timer, and thermometer(s):
- Photographic gelatin
- Potassium chloride (KCl)
- Silver nitrate (AgNO3)
- Distilled water
- Heat source
- 2 Pyrex measuring cups—1 cup/250 ml and 2 cup/500 ml
- Small Stainless steel whisk
- 80 or 100 ml glass beaker, or similar
- 25 ml graduated cylinder, or kitchen tablespoon
- Plastic picnic spoon(s)
- Eye dropper (if you haven't transferred Photoflo 200 to a dropper bottle)
- Kitchen pot with lightproof lid, big enough to hold the two Pyrex cups, stacked
- 90 lb HP watercolor paper, cut to size and grain-coded
- Puddle Pushers (x2), taped and puttied
- Impeccably clean tray, big enough to soak the watercolor paper
- Glass coating surface(s)
- Squeegee
- Sheet of Mylar or similar (I like Graphix® 'Dura-lar')
- Bath towel
- Measuring cup with a handle, ~¼ cup/2 oz/ 50–60 ml (or smaller for smaller coatings)
- Plastic tray or bowl, large enough to rinse the puddle pusher between coatings
- Hand towels
- Optional, but very useful: a clothesline to hang the coated paper for final drying.
To the best your space allows, stage all the components for both the emulsion making and the paper coating. Weigh out the chemistry, line up the tools in the order you'll use them, and have the watercolor paper and glass coating surface(s) ready, along with space to set the glass and coated paper to dry.
PREPARATION
Salted Gelatin
In the 1-cup Pyrex cup, dissolve together
- Distilled water ..... 150 g (150 ml) or 135 ml if you are using vodka instead of Everclear
- Potassium chloride (KCl) ..... 3 g
When dissolved, slowly and thoroughly stir in
- Photographic gelatin ..... 25 g
Cover the container with a piece of plastic wrap or a plastic lid. Let it sit for 30 minutes to several hours to bloom (soak and swell) the gelatin with as much water as it can hold). Fill the 2-cup Pyrex with very warm water and over a sink or tray to catch the overflow water, carefully set in the 1-cup Pyrex with the salted gelatin. Place the Pyrex stack on your heating unit or in a larger container of water preheated to 49–52°C/120–125°F. Poke an impeccably clean thermometer through the plastic wrap into the salted gelatin. When the salted gelatin is melted and has reached 49–51°C/~122°F, you will be ready to add the silver (i.e., the "precipitation" step).
Silver solution
In the meantime, dissolve together
- Silver nitrate ..... 5 g
- Distilled water ..... 25 g (25 ml)
CAUTION: At all times when handling silver nitrate, be very careful. Silver nitrate is a powerful oxidizer and stains anything organic it comes in contact with. If you get stains on your skin they cannot be washed off. They will be part of your skin for weeks. If you get silver nitrate in your eyes, the damage could be blinding. Don't be afraid, just be careful. Silver nitrate is no more hazardous than many common household cleaning chemicals. Bleach and drain cleaner come readily to mind. On a happier note, there are no hazardous fumes involved with a plain silver nitrate solution.
PRECIPITATION (a.k.a. "emulsification")
Where you are at now: The salted gelatin is holding at 49–51°C. The silver nitrate solution is ready and sitting safely within easy reach of your waterbath stack. As is the stainless steel whisk. Have a timer within reach and sight. Set it to be ready to start a 5 minute countdown or count-up. Have boiling water handy. Turn off the room light and turn on the safelight.
Start the timer. Immediately start whisking the salted gelatin in one direction. When you have a good rhythm going, pour in about 1/3 of the silver solution, whisking continuously. Whisk for 1 minute. Pour in another 1/3 of the silver, whisking continuously for a minute. Pour in the remaining silver solution and continue whisking until the end to the 5 minutes. (When I have the time to learn how to add captions to videos, I will indicate that a minute has gone by between additions. For now, bear that in mind as you watch.)
Cover the 1-cup Pyrex tightly with plastic wrap and set the waterbath stack in your kitchen pot. Pour in enough almost boiling water so that the water comes half way up the side of the 2-cup Pyrex. Be careful to keep the water from falling on the plastic wrap. Cover the pot with its lid. The emulsion is now in its ripening stage.
TIP: Rinse the whisk immediately after use. Silver nitrate is very corrosive to cheap stainless steel. If you see any rust forming on your whisk, you should replace it. Emulsion doesn't like rust. You can mix emulsion with a plastic spoon. You just have to practice getting a good rotation going in the melted gelatin.
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