I’ve been using Kodak’s Flexcolor chemistry for 4 years with acceptable results, but have found the variability from day to day and batch to batch to be irritating. I thought it worthwhile to test a simpler formula published many years ago called the “Dignan’s 2 Bath C41 process.” (see http://www.apug.org/forums/forum223/34413-dignan-ncf-41-divided-color-negative-developer-2.html).
Using Kodak chemistry essentially requires mixing a fresh stock solution that must be used within a week’s period, even if developing far less than the the published capacity claims. In low volume operations, this can mean higher cost per roll/sheet, since you are forced to throw away “unused” developer. The modern C41 chemistry workflow requires very careful measurement of 4 solutions, and tight temperature and time controls to make it work reliably in small volume manual operations such as small tank or tray development. If you have an autoprocessor like a Jobo, this may not be important to you. But I still develop my 4×5 negatives in open trays sitting in a tempering bath, and tightly controlling temperatures over several hours is challenging.
As a test, I purchased the chemicals required to mix Dignan’s C41 developer, which requires two stock solutions (A and B). The workflow is far simpler with this formula. First the negatives are bathed in Solution A for a time, then transferred to Solution B for a time. Bleaching, fixing, and stabilizing then occurs as with the Kodak workflow. The 2 batch workflow is claimed to be temperature tolerant: somewhere around 25 degree C and it need not be precise. The instructions prescribe at least 3 min in Solution A and at least 6 min in Solution B, with no wash between solutions. Sol A never exhausts because it doesn’t oxidize nor does it dilute over time. You just keep using it until you deplete the volume, and mix up another batch. Sol B is one-shot because the carryover Sol A on the negatives will consume the buffering power of Sol B quickly.
Most of the discussion on the boards about Dignan’s chemistry are quite old, perhaps dealing with older films, and were not very encouraging. My main concerns, based on the discussions, were 1) low saturation negatives and 2) grainy negatives.
I found both concerns eliminated after a simple test. I shot a full-scale color print (Colormunki print test onto canvas) placed in full sun using a 4×5 camera loaded with Ektar 100 film. I developed one sheet in Dignan’s formula for twice the rated times (i.e., 6 minutes in Solution A and 12 minutes in Solution B) at 30 deg C. The next day, I developed the second sheet closer to the prescribed time and temperature: 25 deg C, 3 min Solution A and 6 min Solution B. Solution B must be fresh, but I used the same solution from the previous day’s work. In both cases (Day 1 and Day 2), the pH of my Solution B was 11.88 at 25 deg C.
Here’s a jpg of the scanned and converted negative from Day 1 (i.e., higher temp and time periods). The colors are fully saturated and the amount of grain was very typical to what I see with Flexicolor chemistry on Ektar (i.e., very fine). There were minor color shifts I had to correct in software, but again, they were pretty typical of what I see using Flexicolor chemistry on Ektar film.
Even with the higher temperature and extended times that I used on Day 1, I still noticed some color mottling across the film frame that indicates uneven development. I saw this especially at the edges of the negative, and this was very obvious with the Day 2 negative, for which I used the published time and temperature specifications (75 deg F, 3 min Sol A, 6 min Sol B). This tells me that I need to further extend either both time or temperature in both Sol A and Sol B. I don’t believe exhaustion of Sol B on Day 2 was the culprit because the pH had not changed. Instead, I suspect that these modern films are engineered to maximize penetration of chemistry into all emulsion layers at high temperatures and short times, since the normal development of C41 is 100-103 deg F for 3:15 minutes. I plan to adopt 100 deg F for 5min (Sol A) and 10 min (Sol B) as an arbitrary start point for further testing. I know this defeats one of the benefits of the 2 Bath workflow (i.e., room temperature processing), but it believe it will be necessary.
If you are searching for alternative C41 developers, you might try this old fashioned formula. It’s very simple, cheap, and should be robust.
Update 10/28/15: I’ve been testing further. My thoughts above haven’t changed, but now I’ve developed a number of real negatives and I’m even more impressed with the NFC-41 workflow. Scans well, minimal grain (Ektar and Portra films). Some of the problems I’m seeing with uneven development have to be worked out. I typically use tray development, and I suspect that even though I’m getting good saturation in Bath A, it’s more important to agitate in Bath B to get even development. A couple of my negatives seem “undeveloped” in the centers of the negatives, where they have the most tendency to stagnate the flow of Bath B while in the tray. Tray development may not work here: either a carrier that can be taken from Bath A to Bath B without the need to manually shuffle the negatives, or perhaps using BTZ-like development tubes. I’ve used BTZ tubes before and they work great, but you have to constantly roll the tubes and that’s a pain.
Warning: There is no real “buffering” power of Bath B. It’s only potassium carbonate and potassium bromide; no buffers. So be sure to use fresh Bath B for every set of negatives. I tried to test the capacity of Bath B by running several negatives before changing to fresh. The pH went from 11.9 (fresh) to 11.2 (used), and the last negatives were extremely thin. The bath volume was about 500 mls, and probably 5 drained negatives went through it. So, don’t trust that Bath B has much more capacity than a couple negatives..test it in your own workflow. One idea for stabilizing Bath B capacity would be to adopt a suitable buffer, e.g. Sodium bicarbonate: Sodium Hydroxide. The range of pH for this pair is 9.8-11, adjustable by the amount of NaOH added. Kodak Flexicolor pH is 10.03, and that should be the target pH of the bicarbonate buffer used in a putative “improved” Bath B. I might try this. it would be extremely cheap and convenient since the ingredients are available as baking soda (sodium bicarb) and Red Devil ® Lye.
Update 11/5/2015: After several more negatives, tray developed at 100 deg F for 6 minutes in both Bath A and Bath B, I haven’t stabilized the process. The image on the negatives has consistently been thin using this approach. That can be a good thing if you’re scanning your negatives like I do, but what’s happening with my technique is that I’m getting “too thin” negatives. I’m giving up on this for the time being…may return for further experimentation later.