Hi all,

I have a question that's been bugging me for some time and am hoping the answer is much more obvious than I realize. I recently learned how to make gelatin dry plate emulsions for large format glass negatives (bromo-iodide).. However as the speed for these dry plates can vary in terms of a few variables during their emulsion "cooking" time, namely time and temperature and fog density, there can be considerable differences in how I expose each batch.

I'd like to determine the sensitivity of each emulsion batch as I finish preparing it so I can account for the exposure differences, but am foggy on how to go about it. In school I recall using the zone system to determine a personal ISO based on a given camera, film box speed, paper/chemistry combination. But where do I begin if I don't have a ballpark ISO to work from? Additionally, this film is primarily blue UV sensitive.

My exposures with my recent emulsion batches have been about f/5.6 @ 3", if that's at all helpful. I'd appreciate any helpful approaches to how I might go about determining the speed of my emulsions. And please go easy on me if I'm being especially ignorant!!--it has been a while since I've been immersed in the zone system practice but I'm really eager to understand this and maintain some consistency in the exposures for my dry plates.

Thank you in advance, LF photo community!