Contact Printing Paper

I ♥ Emulsion

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Don't forget to have fun with all this. Play around with small batches. Following a few parameters, which you'll soon become familiar, substitute within chemical families and vary weights, temperature, and timing. You'll probably see your share of disasters, but then again, it's much more likely you'll see some great successes. (Take good notes!)

I ♥ Emulsion

A Neutral Tone Developing-Out Contact Printing Paper

Gel A: 13 g gelatin / 75 g cold distilled water

  • Bloom gelatin in a covered canning jar for 1 hour starting with refrigerated distilled water.
  • Melt to 42-43°C in a water bath on a 90°C hot plate (starting with 40°C waterbath).

Gel B: 13 g gelatin / 75 g cold distilled water (or: 65 g if coating wet paper).

  • Bloom gelatin for 1 hour.

Have ready:
  • Fine nozzle Monoject syringe marked at 10 ml.
  • Two canning jars with plastic wrap and lid bands.
  • Stopcock burette, primed with distilled water, ready to swing over beaker.
  • Two lightproof refrigerator canisters, filled with about a half inch of very cold water. (Store the empty — except for water — canisters in a refrigerator until right before you go to safelight.)
  • Weighed chemicals:
3.9 g Sodium chloride (NaCl) / 12 g distilled water (room temp)
0.5 g citric acid (dry)
0.5 g citric acid/ 10 ml water
1.0 g Potassium bromide (KBr)
5.6 g Silver nitrate (AgNO3) / 20 g distilled water (room temp)

In 50 ml beaker, dissolve NaCl in water — set at room temp. (This is a very nearly saturated solution. Stir with the clean handle of a plastic spoon until the NaCl dissolves. Add additional water, drop by drop, with stirring if necessary to just dissolve the salt.)

In 50 ml beaker, dissolve AgNO3 in water — warm to 40°C.

Dissolve 0.5 g citric acid in 10 ml water — warm to 40°C.

  • Strain Gel A through a tea strainer into a 250 ml beaker in the waterbath on the magnetic hot plate. Turn off heat. Start stirring at medium low speed, making sure vortex is centered on the center of the beaker.
  • Add in this order: KBr, 0.5 g citric acid, and dissolved NaCl.
  • Suck up 10 ml AgNO3 solution in the syringe and set aside upright in a clean beaker.
  • Add the warm citric acid solution to the remaining 10 ml AgNO3 solution and pour into the primed, closed burette. Swing the burette over the beaker so that the stream will hit the gelatin about 1/2 inch in from the wall of the beaker.
  • Spritz gelatin with Everclear.

GO TO SAFELIGHT

  1. Turn on burette.
  2. Immediately begin silver injection at the very bottom of the beaker, between the rotation path of the stirring rod and the beaker wall/floor edge. Over 1-1/2 to 2 minutes, slowly and evenly inject 10 ml AgNO3 solution. Aim for the burette and the syringe emptying at about the same time.
  3. Stir an additional 3 minutes.
  4. Fluff the bloomed Gel B with the tines of a plastic fork. Over 2 minutes, add it to the melt. When it's all been added, stir the top of the mix and press any fresh gelatin under the surface. Stir an additional minute. (i.e. 3 minutes total.)
  5. Take the beaker of melt out of the water bath. Let settle 1 minute.
  6. Strain through a tea strainer into a clean pouring beaker and immediately divide between two 8 oz canning jars. Cover each with plastic wrap secured by a lid ring and immediately refrigerate in cold lightproof canisters pre-filled with a half inch of cold water. Store in the refrigerator at least 8 hours. Storage time is to a certain extent an emulsion characteristic variable, so try to be consistent or take good notes. Emulsion can be stored for at least a week without a preservative. I've never used thymol or any other preservative, so I don't know the effect, if any, on my recipes.

ADDING FINALS BEFORE COATING

Preheat magnetic stirring plate with waterbath for 250 ml beaker to 50-52°C.

Preheat hot plate to 65°C.

Have ready:

  • Dropper bottle of 1% Potassium iodide (KI).
  • Dropper bottle of Photoflo 600.
  • Dropper bottle of glyoxal.
  • Coating tools and surfaces.
  • Precut paper and small pieces of adhesive tape (I tear off about 36 1-inch pieces and line them up on the clothesline over my sink.)
  • Small jar of Everclear.
  • 250 ml beaker with stirring rod.
  • Strainers (tea and gold mesh coffee filters) and plastic canning funnel.
  • Hot distilled water.
  • Wash buckets (one with hot soapy water, one with hot clean water).
  • A 250 ml beaker nested inside a 400 ml beaker with enough water (room temp) to come within a 1/2 inch of the top.

GO TO SAFELIGHT

Melt one jar (1/2 batch) of emulsion: Remove jar from the lightproof container and place in a 40°C waterbath (have the water level at about the height of the top of the emulsion). Stick a thermometer through the plastic wrap into the emulsion. When the temperature of the emulsion hits about 38°C, remove the plastic wrap and gently stir with a clean plastic spoon until the emulsion is 41-42°C.

Strain the melted emulsion through a stainless steel tea strainer into the 250 ml beaker in the waterbath on the magnetic hot plate. Start magnetic stirring at medium low (it remains stirring throughout the finals step.) Keep the waterbath temperature at 49-51°C. Add 15 drops 1% KI solution at about a drop per second, stir one minute. Add 12 drops Photoflo 600, stir one minute. Add 15 drops glyoxal and then spritz the surface of the emulsion with Everclear. Remove the beaker from the water bath and wipe the outside dry. Pour into the 250 ml in 400 ml beaker jacket through a stack of two or three gold mesh coffee filters. Spritz with Everclear. Set the water jacket on a hot plate set at about 65°C. The water should warm up at the same rate as the emulsion cools. A little experience with your workflow will quickly help you determine your temperature parameters.

The first coating pass with tell you two things:

1) Is the emulsion cool enough? If the coating is too warm it will go on too thin and you'll be able to see the dull paper through the shiny emulsion. Just wait a couple of minutes, give the emulsion a gentle stir with a clean plastic spoon, and try again. Mark this first sheet because it's not wasted. It can be cut into test strips when you start printing.

2) Is the surfactant right? If you see air bubbles or spots (repellency indicators) add another drop of Photoflo 600 and give a gentle stir.

A few tips:

  • Tiny bubbles, often in a cluster, indicate that you probably added air in the emulsion take-up. Have an atomizer bottle of Everclear close at hand and immediately spritz the bubble patch from about 4 inches. The bubbles should disappear. If they remain, don't try again. After the emulsion starts to set, Everclear can leave its own marks on the surface. Make note as to the location of the defect and avoid printing on that area.
  • Keep a black permanent marker close at hand. Right after coating, the surface of the emulsion is shiny and any and all defects are plainly visible. It is a simple matter to make a map along the uncoated edge of the paper to guide your printing.
  • After the paper is dry, and you start to stack the sheets for storage in a paper safe (or light proof bag) triage the sheets. Start with the 'ugly' ones on top. These will be your test strips and you'll soon value them. They eliminate the stress of cutting up perfect sheets for testing ;-)


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