Materials List to Make the Chloro-Bromide (ClBr) Emulsion for my Large Format Paper Negatives

December 15, 2015  •  Leave a Comment

This is a brief article to provide an update on the making of the ClBr (Chloro-Bromide) silver gelatin emulsion for my large format paper negatives. 

I am creating the emulsion based on the recipe found in the SPSE handbook of Photographic Science and Engineering, 1973 edition, which I found in Denise Ross's The Light Farm Book, Volume 1.   

I choose this emulsion because of the light spectrum mostly.  Silver bromide (AgBr) has a wider spectrum than silver chloride (AgCl), which covers UV and violet, but the ClBr emulsion also sees into the blues making it a perfect choice for my style and creative vision.  My plan is to develop these paper negatives with D23 that I mix from raw materials.  I plan to make Stouffer wedge contact prints to illustrate the tonal range (toe and shoulder) and publish them.  

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I will first be printing on a known paper before moving to the next step and creating the emulsion for my prints and hand coating that paper.  At this time, I will most likely be creating a silver chloride (AgCl) emulsion for my large format contact prints and be developing in Amidol and possibly exploring other options.  I like Amidol with silver chloride papers because I have a great degree of control over the tones (warm to cold blacks) in my prints, just by modifying the chemical formula.  

Ingredients List for ClBr Emulsion

- Distilled water
- Photographic grade gelatin
- Sodium Chloride (table salt)
- Potassium Bromide
- Citric Acid
- Silver Nitrate
- Photo-flo 200
- Glyoxal (optional for hardening) - 40% solution

After I make a few batches, I will write another update and hopefully have a stable master formula that I want to continue to use.  More to follow soon!

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Tim Layton
Darkroom & Large Format Photography
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