Mark Osterman's Dry Plate Emulsion Recipe

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'Turning The Tip'
Print from a plate exposed in a skylight studio
by Mark Osterman

Mark Osterman has been the process historian for the George Eastman House International Museum of Photography for the past ten years.  The following recipe was developed by Mark and the procedure and emulsion formula was tested by giving a set of the instructions and the materials to graduate photo students at the Visual Studies Workshop in Rochester who had never made an emulsion before.  As with the very best of the old emulsions, 'speed' was not the goal.  Rather, Mark set out to produce a beautiful, clean-working emulsion suitable for printing with any number of traditional processes.  He succeeded wonderfully. 

The recipe is part of a concise and comprehensive article on dry plate making posted in the Articles section (here).  I highly recommend reading the entire article before you start cooking.  The article, in a condensed form with illustrations, is included in the 2nd edition of The Book of Alternative Photographic Processes, by Christopher James.

Osterman’s 1880 Gelatin Bromide Emulsion

Equipment and Materials Needed

Much of this equipment can be used for other historic photographic processes. The hot plate/stirrer, for example, is one of those pieces of equipment that is a great help for mixing all sorts of things. Pyrex glass beakers in assorted sizes are essential in every historic process darkroom. The crock pot and potato ricer are however specific to gelatin emulsion making, an activity very similar to cooking.

  1. safety goggles
  2. latex gloves
  3. Pyrex "tempered glass" laboratory beakers; one 500 ml & two 300 ml size.
  4. 1½ quart Pyrex "tempered glass" loaf baking dish for chilling
  5. heat source*
  6. thermometer (digital thermometers are cheap and perfect for emulsion making particularly when they have a built-in alarm)
  7. 3 quart glazed ceramic or stainless steel mixing bowl
  8. stainless steel wire mesh drainer big enough to rest in the opening of the aforesaid mixing bowl
  9. small brown ceramic cheese crock with wire locking ceramic lid
  10. 1 square foot of black plastic sheeting (must be opaque)
  11. 1 gallon bag made of black plastic sheeting (must be opaque)
  12. large plastic syringe (60ml/cc)**
  13. heavy duty stainless steel potato ricer
  14. refrigerator (a small dormitory type is perfect or use your household refrigerator) and ice cube tray
  15. electric crock pot
  16. 25" square piece of sheer white nylon or polyester cloth (for filtering)
  17. stainless steel spoon
  18. glass stirring rods
  19. red or deep amber safe light
* You can use a sauce pan on a hot plate or the crock pot (also listed) but a laboratory hot plate w/magnetic stirrer is perfect for emulsion making and well worth the expense. You can purchase them second hand on line.
** The Terumo brand 60 cc Syringe with Catheter Tip is perfect except that the opening of the tip is too wide. Go to the hardware store and buy a tube of glue that comes with a separate tapered tip of the same size. Make a pin hole in the end of the tip with a hot needle and push this firmly over the catheter tip of the syringe.

The quantities listed below are for making one batch of approximately 350 ml emulsion. Naturally it is a better plan to buy larger amounts any time you buy these materials as they are generally less expensive when purchased in quantity.
  1. 1 liter distilled water
  2. 10.5 grams potassium bromide
  3. 0.4 grams potassium iodide
  4. 12 grams silver nitrate crystals
  5. 21 grams gelatin (photographic grade is best, but you can use food grade)
  6. 5 grams chrome alum
  7. 1 grain thymol
  8. 5 ml 95% grain alcohol

Making the Emulsion
Take the time to read and visualize all of the following steps before you attempt to make the emulsion. You may want to practice step 5 with plain water to feel comfortable with the technique. Preparing all the materials and equipment prior to working under safelight conditions will make the procedure much easier to perform.

1. Put 3 grams photographic grade gelatin into a 500 ml Pyrex glass beaker with 85 ml distilled water. Allow at least fifteen minutes for the gelatin to become fully swollen and easily flattened (or squished) between the fingers. This is called the "first melt" gelatin.

2. Put 18 grams photographic grade gelatin into a 300 ml beaker and pour enough distilled water to cover the gelatin. Allow this gelatin to absorb as much water as possible. Different sources of gelatin absorb more water than others. You may need to add more water at a later time. This is called the "reserve" gelatin which will be drained and added to the emulsion after the first melt.

3. Dissolve the swollen first melt gelatin by placing the beaker in a hot water bath such as a small sauce pan with water on a hot plate or in a crock pot with just enough water to the level of the gelatin solution. You may also use a hot plate stirrer as long as the solution is kept in motion with the magnetic stirrer. Using a thermometer, try to keep the temperature around 120 degrees F.

4. Put 10.5 grams potassium bromide and .4 grams potassium iodide in the first melt gelatin and stir the solution until the halides are fully dissolved.

[Every operation after this should be done under red safe light. The darker the safe light and the less time you have the emulsion exposed to it, the better]!

5. Prepare the silver solution by dissolving 12 grams silver nitrate in a 300 ml Pyrex glass beaker with 85 ml distilled water. Heat this silver solution to around 120 degrees F (50 C) and draw some of this solution into the syringe. Slowly squirt the heated silver solution in a continuous stream with the tip below the surface of the gelatin halide solution while you stir it continuously (this is where a hot plate stirrer comes in handy). Refill the syringe and continue until all the silver solution has been added to the gelatin-halide solution.

[When making more sensitive emulsions you can be more accurate if you use a musician’s metronome to keep you on track as you gently and continuously push the plunger of the syringe. Try to make the plunger pass a ml marking on every click, or every other click, of the metronome.]

6. As you combine the silver with the gelatin-halide solution you will see the two clear liquids change into a milky white silver bromo-iodide emulsion.

7. After all the silver has been added, ripen the emulsion by maintaining the temperature at around 120 degrees F for 15 minutes with constant gentle stirring.

8. While the emulsion is ripening, begin draining all the excess water from the reserve gelatin. When digestion is complete, add the reserve gelatin to the emulsion and stir until the new gelatin is completely dissolved. When you first add the reserve gelatin the temperature of the emulsion will fall. Bring up the temperature of the emulsion back to 120 degrees F. and dissolve the reserve as quickly as possible. Make a notation of the time it takes for future reference.

9. Pour the hot emulsion into the glass Pyrex loaf pan and carefully slide this into the black plastic bag. Secure the opening of the bag so that no light can fog the emulsion. Place the bagged emulsion in the refrigerator for several hours or until completely set to a stiff jelly. The reason a shallow dish is used for setting the emulsion is so that it will chill faster and more evenly than if left in the beaker.

[In the following steps it is advisable to wear latex gloves; not because of potential silver stains to the hands, but to prevent contamination of the emulsion from your hands.]

10. Under red safe light remove the emulsion from the refrigerator and pull the dish from the bag. The emulsion will look white under the safe light (it is actually bright yellow). Scoop out the firm jelled emulsion with the stainless steel spoon and put it into the potato ricer.

11. Place the sheer white nylon fabric in the stainless steel wire mesh drainer in the mixing bowl and squeeze the ricer to create emulsion noodles that will fall into the center of the fabric. When the emulsion is completely noodled into the fabric, gather the edges of the cloth and secure them with a rubber band. Fill the bowl with cold tap water (add a few ice cubes) and move the noodle filled fabric around for about five minutes then let soak for five more without agitation. Change the water two more times and wash the noodles as before.

12. Drain the washed emulsion noodles thoroughly for at least 15 minutes and then place them into a clean Pyrex beaker.* Re-melt the beaker of emulsion in the electric crock pot at around 120 degrees F and add "finals." The finals listed below are: chrome alum, added to make the emulsion set to a stronger film to withstand processing, alcohol to aid in coating and thymol, to prevent bacteria growth.

[No chrome alum in the emulsion may result in a very fragile film that can melt off the plate if processed in chemicals or washed in water that is too warm. Too much chrome alum will prevent the film from absorbing the chemicals effectively. Because the characteristics of each sample of gelatin are going to be different, the quantity of chrome alum may need to be decreased or increased as needed.]

* An old stainless steel developing tank is great for re-melting emulsions. The light trap in the lid allows you to keep the white lights on in the darkroom

   4 ml of a 5% solution chrome alum (5 grams chrome alum into 100 ml distilled water) Add the chrome alum drop by drop
   5 ml 95% grain alcohol
   1 grain thymol

When the finals are added and fully incorporated into the emulsion pour the entire contents into a brown ceramic cheese crock, cover the opening with a piece of black opaque plastic and secure the ceramic lid with the wire spring. Place the emulsion filled crock in the refrigerator for future use. Remove only what’s needed when coating a batch of plates by scooping out the chilled emulsion with a stainless steel spoon. The stock emulsion will last many months if kept cool and protected from white light.

These plates are blue, violet and ultra violet sensitive and fairly slow by modern standards. Assume an ISO rating of between 5-10 as a starting point. They are developed under red safe light, by inspection, which is a great advantage.


Mark’s way of introducing silver nitrate solution into the halide/gelatin mix.  The glass tip on the exit rod is drawn to a fine opening.  When the operator squeezes as hard as possible, the addition is very consistent between batches...much easier than a plastic hypo syringe.


Storage crocks for emulsions and an invalid cup used for coating plates (pours from the bottom).


Marble top leveling table for chilling emulsion plates.


Detail of leveling screw.


Plate rack.

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