A few years ago I began an aging study on four cadmium free collodion formulas to see how fast they age. I have data for some of the formulas at various times, but I wanted to do a more controlled experiment at more frequent intervals so that I could see at what point a particular collodion slowed.
The four formulas:
- Lithium Chloride modified
- Ammonium Chloride modified
- UVP #1 (Ammonium Iodide, Lithium Bromide)
- UVP #3 (Lithium Iodide, Lithium Bromide)
I was going to wait until I finished the study before posting anything, but one of the formulas surprised me. I was expecting the UVP #1 to behave like it’s cadmium containing brother, remain fast for a short while, and then slow after a few weeks. It didn't. It started out at what I consider to be a normal speed, and then at 2 weeks it got noticeably faster. I was using the same silver, dev, fix, temp, etc., and the speed increase wasn't consistent across all the formulas being tested, so I don’t think it was a flaw in my setup. I have seen the UVP #3 speed-up slightly over time, but never really paid enough attention to the UVP #1 to notice a change. I typically have a new batch of something to shoot, so I never saw this in my own shooting.
My procedure is to shoot to get a correctly exposed plate using a stopwatch, and then the following week I start at that exposure, and adjust if needed. Since I can’t get every plate 100% exact, I grade +/- vs the others in the set to determine fractions of a second. I don’t think any plate is more than ½ second exposure away from where it should be, so I think it’s an appropriate way to adjust for fractions of a second.
At 5 weeks all of the formulas are as fast as or faster than when mixed. Also, I like the look of the plates at two-three weeks better than the one day or one week plates. It's subtle, but there is a quality difference. The two chloride formulas are consistent and seem to be fairly stable. I plan to do a separate write-up on these formulas once I understand them a bit better. I think they may have some advantages in contrast and crispness (I can't think of a better way to describe what I see).
The collodion is not being stored in a refrigerator, but it is being kept in a cool dark-ish location.
I plan to continue until all the formulas slow. In the meantime I’m going to start another aging study using some of the most popular formulas being used today. Old Work Horse, Old Reliable, QQC, and UVP #1 as my control. It should be interesting!