Gel A:  13 g gelatin / 75 g water

• Bloom 1 hr. starting with refrigerated distilled water.
• Melt to 43C in waterbath on 90C° hot plate (starting from 40C water).

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

• Bloom gelatin for 1 hour.

Have ready:

• 250 ml beaker with centered stirring rod in waterbath on magnetic hot plate at 52-53°C.
• Monoject syringe (fine nozzle variety marked at 10 ml).
• jars, plastic wrap and jar lid bands.
• weighed chemicals.

Dissolve NaCl in water – set at room temp.

Dissolve AgNO3 in water – warm to 40C.

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

• Strain melted Gel A into beaker in waterbath on magnetic hot plate. Turn off heat. Stir at medium low speed.
• Add in this order: NH₄Br, 1.0 g dry citric acid, and dissolved salt and KCl.
• Suck up 10 ml AgNO₃ in syringe, set aside.
• Add warm citric acid solution to remaining 10 ml AgNO₃ solution, and pour into primed, closed stopcock burette. Swing the burette over the beaker so that the stream will hit the gelatin about 1/2-inch in from the from the wall of the beaker.
• Spritz gel mixture 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 has 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 stainless steel 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.

ADDING FINALS BEFORE COATING

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

Preheat hot plate to 95C.

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 40C 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 38C, remove the plastic wrap and gently stir with a clean plastic spoon until the emulsion is 41-42C. 

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 49-51C.  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 65C.  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 coat the next sheet.  Mark the first sheet because it isn't 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 during 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 of 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 ;-)
• One defect that doesn't show up until printing is "slugs".  If you see them, you'll recognize them.  Good straining all but eliminates the problem.