Just ran an interesting experiment, where I created two emulsion batches with the only difference being the source of the gelatin. Both are hard bloom gelatins: B&S supplies ossein gelatin (cow bones), Photographers Formulary provides gelatin made from sow. I could easily speculate on the supplier source, but I won’t here.
The emulsion was my dry plate recipe, a Bromide-Iodide emulsion similar to Osterman’s, Eder’s, Mees, AJ-12, etc... i.e not an ammonia digest recipe. All times and temperatures, processes, etc were kept the same through all stages of the make for both batches. These are unsensitized batches: No dyes, sulfur or gold added.
I coated two plates, one from each batch, exposed them both to the same light levels with the same exposure time (my emulsion characterization setup), then developed at the same time in the same SP-445 tank.
Here are the results, fresh from rinse. The plate coated with the Bostick & Sullivan based batch is on the left, and Photographers Formulary based batch is on the right (you can see the batch numbers written on the back of the plate).
Visually comparing steps, I estimate a two stop difference in speed. I’ll take densitometer measurements when they are dry.
For you emulsion makers, is this in line with what you’ve experienced?
Cheers,
Jason
The emulsion was my dry plate recipe, a Bromide-Iodide emulsion similar to Osterman’s, Eder’s, Mees, AJ-12, etc... i.e not an ammonia digest recipe. All times and temperatures, processes, etc were kept the same through all stages of the make for both batches. These are unsensitized batches: No dyes, sulfur or gold added.
I coated two plates, one from each batch, exposed them both to the same light levels with the same exposure time (my emulsion characterization setup), then developed at the same time in the same SP-445 tank.
Here are the results, fresh from rinse. The plate coated with the Bostick & Sullivan based batch is on the left, and Photographers Formulary based batch is on the right (you can see the batch numbers written on the back of the plate).
Visually comparing steps, I estimate a two stop difference in speed. I’ll take densitometer measurements when they are dry.
For you emulsion makers, is this in line with what you’ve experienced?
Cheers,
Jason
Last edited: