Dry Plate Photography

The Light Farm Negative Emulsion Recipe #1

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5"x7" plate, TLF #1 Negative Emulsion
To date, I have done most of my dry plate explorations with The Light Farm Glass Negative Emulsion #1 (a.k.a. 'TLF#1').  I love this recipe.  I've always treasured slow, fine-grained films and I miss Kodak Technical Pan film (ASA 25).  The sections following the recipes are all from my work with 'TLF #1'.

The Light Farm Glass Negative Emulsion #1

Modified from Photographic Emulsion Technique, 2nd Ed
T. Thorne Baker, 1948, page 82.

Note: This recipe has been modified from the original version in the 'Glass Negative' Section.

For Approx. 200 ml of emulsion.  That's about 16 4"x5" plates, or 10 5"x7" plates, or 8 Whole plates (6.5"x8.5").

Preheat a waterbath on a magnetic hot plate to 45C. Weigh out ingredients.

Part D: Distilled water, refrigerator temp 20 ml
  Gelatin 15 g

In a beaker (150 to 250 ml size) or a container that is easy to scrape out, swell gelatin at least 30 minutes at room temp.

Part A: Distilled water, refrigerator temp 40 ml
  Gelatin 2.5 g

In 250ml beaker, swell gelatin 30 min. Add:
Ammonium bromide 7.0 g
Potassium iodide (KI), 10% solution 1 ml (20 drops)

Melt to 43C in waterbath, with occasional, gentle stirring.

Part B: Silver Nitrate 5.2 g
  Distilled water, room temp 5 ml
  Ammonia, 28% 5+ ml

Measure 5 ml ammonia into a 10 ml graduate cylinder. Have a dropper bottle of ammonia ready and waiting.

Dissolve the silver in the water (by stirring with the handle of an impeccably clean plastic spoon). Slowly, with stirring, add 5 ml ammonia. (Excellent ventilation is a very good thing here.) With the first few drops of ammonia, the solution will turn a muddy black from the precipitate that is formed. After the first 5 ml has been added, starting with two drops at a time, add more ammonia, stirring and observing after each addition. When you see that the solution is starting to clear, slow the addition to one drop at a time, with stirring. The ammonia is dissolving the precipitate. There will only be one drop between being able to see a few remaining black flecks and total clearing. It is important to avoid excess ammonia. When the solution is clear, cover (I set a glass coffee cup saucer on top) and set aside at room temp.

Part C: Silver nitrate 5.6 g
  Distilled water, room temp 22 ml

Dissolve, cover, and hold at 43C.

Turn the heat off the waterbath. Make sure the temperature is not above 43C. If it is, add a little ice water. (I keep a wash bottle in the refrigerator to cool down the water bath if necessary. Temperature control is our friend.)

Under red or dark amber safelight:

Making sure you know which is which, have Parts B and C at the handy. Over 5 seconds time, with slow stirring, add Part B to Part A through a small funnel held right above the gelatin mixture. Immediately add Part C in the same manner. Stir an additional 30 sec. Stop stirring. Pull the waterbath off the hot plate. Ripen the mixture without stirring for 15 minutes. Make sure the waterbath temperature stays between 40 and 43C. (Make a note of the temperature curve over the 15 minutes for future reference and recipe refinement.)

Note: There are a number of variations to the above.  You can add B with a monoject syringe, like in making paper, and then follow with C in another syringe, or a stopcock buret.  Each technique will yield its own characteristic results.  Experiment freely. Take good notes.

Add 2 drops 10% KI.

Fluff (or chop, if necessary) the Part D gelatin. Sprinkle/scrape it into the hot mix. Gently press in under the surface and give a gentle stir. Ripen without stirring another 15 minutes. (With a gentle stir and scrape from the bottom every 5 minutes.) The heat should stay between 40 and 42 degrees. It may be necessary to slide the waterbath back onto the hot plate.

Pour the melt into a ziploc sandwich bag resting in ice water. Seal bag. Refrigerate in a light proof container 4 - 24 hours. (You probably can leave the emulsion for up to a week, but time is an emulsion variable. The emulsion will fog if you hold it too long.)

Second Session: If you are planning on coating immediately after washing the noodles, preheat the waterbath on the magnetic hot plate to 55C. Have a 400 ml beaker ready.

Washing the gelatin: Under safelight, put the baggie of refrigerated silver gelatin in another lightproof container at room temperature and let warm a bit (approx. ½ hour). It will be too stiff to noodle otherwise. Bear in mind the time/temperature component of ripening. You don’t want the gelatin to get too warm or sit around too long or the sensitivity curve will become an unknown — at the worst to the point of fog. If the lump of gelatin is still too hard to squeeze through the ricer when you get started, you can tear off smaller pieces with your fingers, making very sure you don’t drop any.

Have a large quantity of ice water available (tap water or filtered, depending on your water quality — distilled is not required and may even be detrimental). I fill a Coleman drink container with crushed ice from the corner market and keep it covered with tap water through the washing cycles. Set a cotton jelly straining bag in a half gallon size Coleman cold thermos, turning the top of the bag over the edge of the thermos. Pull the drawstring securely and tie with a bow tie. Fill with ice water (strain out any pieces of ice). Set the open potato ricer bowl in the ice water in the thermos. Go to safelight.

Open the baggie of gelatin and turn it out into the ricer bowl. Keeping the ricer holes under the ice water, squeeze out the threads’ ‘noodles’. With a little rubber scraper or plastic spoon make sure all the gelatin gets into the jelly bag. Pull the drawstring very tight and tie in a bow tie. Wrap the neck tightly with a rubber band. Drop the bag in the ice water and put the lid securely on the thermos.

Over the next approximately 1 and a half hours, wash the noodles. (Note: I have checked the pH after each 5 minute change of water, and the pH lowering curves were identical from 10 to 7.8 for two separate trials. You need to get the pH between 7 and 8, but overwashing is to be avoided. I don’t think it is necessary to check the pH if a careful and consistent wash cycle is maintained.)

Set a timer for 5 minutes, and agitate the thermos like you would a big cylindrical film development tank. This is much harder to describe than to do: Hold the thermos horizontally in front of you, one hand on the bottom and one hand on the lid. Tip back and forth with a quarter-clock rotation with each tilt. This is a gentle exercise; it just assures that the water is moving inside the container, but not beating up on the contents.

After 5 minutes, open the thermos and pour off the old water. Remove the jelly bag and gently squeeze out some of the water. (The point isn’t to squeeze it completely dry). Strain in new ice water and repeat cycle. It takes me about 1½ hours to make 12 water exchanges.

For the first two 5-minutes washes, I agitated the entire time. After that I agitated one minute, let the thermos sit for three minutes and agitated again during the last minute. Since the thermos is light tight, this allows time for breaks and for staging the coating process. Just make sure to go back to safelight each time the thermos is opened.

After the last wash, remove the bag and squeeze out as much water as possible with the potato ricer (cleaned thoroughly since ricing step). Then, roll the bag in a cold, clean terry towel, and gently knead a minute. (I keep a terry towel in a plastic bag in the freezer until the last noodle washing session.)  Open the bag and carefully turn the noodles into a 400ml (or larger) beaker (a wide mouth plastic canning funnel helps). Have a bowl of ice water and a gold mesh coffee filter at hand. Turn the bag inside out under the ice water and agitate gently to wash the noodles off the bag. Strain the wash water through the coffee filter and return the captured noodles to the beaker. Check the sides of the funnel and scrape down any noodles that have clung to the sides. (Note: don’t wash them down.) The point of all this is to get as many last pieces of silvered gelatin as possible. The gelatin/water balance will greatly affect the coating process.

Digestion/Chemical Ripening and Coating

Set the beaker in the 55C waterbath. Watch the temperature of the bath. It will immediately drop below 40C. Turn the heat up and place a separate thermometer in the gelatin. Gently stir the gelatin every 5 minutes until it hits 40C. (With the handle of a plastic spoon, slowly sweep clockwise around the inside of the beaker, make an X across the bottom, followed by another slow sweep around the sides, this time counterclockwise.) Drop in a magnetic stirring bar and add

6-7 drops Steigmann standard aurous ammonium thiocyanate solution 1

Slowly stir for one minute.

Complete digestion without stirring: Continue to bring up the temperature of the waterbath to 52C, keeping a watchful eye. When the temperature of the emulsion hits 50C start to bring the temperature of the waterbath up to 53C and begin to gently stir the emulsion. The emulsion will probably hit 52C before the waterbath hits 53C. Have ice handy to drop into the waterbath if the temperature overshoots 53C before the emulsion hits 52C. When the emulsion hits 52C, remove the beaker from the waterbath. With a gentle stir every 5 minutes, watch the temperature until it hits 40C. Stir in thoroughly,

6 ml Everclear

Strain through a gold mesh coffee filter into another 400 ml beaker set in a waterjacket at 36 -38 C.  Coat plates or film.

Turn out all the lights and go away for 8-plus hours.  If you are coating plates arranged on a silicon mat, you will need to lift them off after 8 hours and prop them up or lay them on a screen so that any emulsion that spread to the back of the plate can dry before loading or storage.

1) Steigmann standard aurous ammonium thiocyanate solution:

From SPSE Handbook of Photographic Science and Engineering, Edited by Woodlief Thomas, Jr., 1973, pp 518-519.

Add 6.0 ml of a 1% gold chloride solution to 50 ml of a 1% ammonium thiocyanate solution, allowing it to clear before using. (Store in dark dropper bottle.)

Note: 1% gold chloride solution is available from Photographers’ Formulary.  1% ammonium thiocyanate is made by adding 1 g of dry a.t. to 99-100 ml distilled water (at ~ 52C/125F) and cooled before use.

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