From my point - I can't understand the problem? Fellows you all have a darkroom! You all have the experience!I think I'll just forego the academic exercise and stick with separate bleach and fix, which is proven to work. I suspect I can afford the additional 4 minutes and extra bottle.
Alan if you have the ability to create an other competend test in concern of long live I would be interested!As I mentioned, I have a spectrophotometer, and I could do the spectral measurements if someone wants to supply the appropriately exposed and developed film. If anyone is interested then let me know.
To be meaningful the test would have to satisfy certain requirements. For example, shooting random scenes would not work.
Here are a few minimum requirements. At least Two rolls would need to be supplied, each roll would need to be exposed under identical conditions. Frames would need to be exposed in solid colors (absolutely no details present in the images). Several different colors would need presented, each in a different image. The colors should have good spectral coverage, i.e. a frames in pure red, a pure green, a pure blue, and maybe some other mixed colors. (I am over-simplifying a little bit here.) Roll 1 would need to be processed in conventional C-41 by a highly reliable lab that uses only the best quality consumables and practices. Roll 2 would need to be processed using a C-41 kit that uses blix using only freshly prepared chemicals whithout re-using solutions.
As I mentioned, this is a minimum requirement. A better program would be that the rolls be grouped into three groups. Every roll would need to be exposed identically, as indicated above. In each of the three groups there would need to be at least three rolls, and in each group each roll would need to be treated absolutely identically. (The purpose of this is a replication study.) Group 1 would be rolls that have undergone conventional C-41 processing. Group 2 would be rolls that have undergone processing with a C-41 kit that uses blix, as described above. Group 3 would be similar to group 2 except that the film would undergo two separate blix steps. The first step would be using once-used blix (but otherwise fresh). The second step blix step would be using absolutely fresh unused blix. Ideally, between the two blix steps there would be a water wash. This is to simulate what would happen if one were to run a process in an automated machine that normally uses separate bleach an fix, but with blix substituted for both the bleach step and the fix step.
This scheme would be used to check for similarity of color produced by the different processes. It would not evaluate which color is "best", and it would not evaluate other factors, such as grain or long term image stability or other factors.
It's probably feasible to evaluate grain by a slight extension of this scheme, but it might be more expensive because it might require drum scans, although a high quality prosumer scanner such as a Nikon or Minolta (or even a Canon) might work. However, it would require someone to become involved who has enough image processing experience to be able to extract some statistical information, i.e. the pixel-to-pixel standard deviation of the images.
If anyone is interested then we can discuss it further, including a more detailed/stringent specification for the study.
What I would like to see is actual experimental results presented using current blix formulations, run using freshly prepared blix solutions in single shot processing, including both a single 6.5 minute blix step at 104 F and two 6.5 minute blix steps at 104 F using separate blix solutions. The resulting samples should be analyzed for retained silver, bromine, and chlorine. The analysis should be done by neutron activation analysis (NAA) because NAA is an elemental analysis that does not depend on extraction of the target analytes from the sample.
As an alternative to neutron activation analysis the silver content could be analyzed by digesting the sample with concentrated nitric acid and then performing the analysis by inductively coupled plasma mass spectrometry (ICPMS). The iodine content could probably also be analyzed by ICPMS. I'm not sure if ICPMS would work for chlorine or bromine. A third alternative would be to analyze for silver in a digested sample using atomic absorption spectroscopy.
The method above should also be performed on samples of film processed by a conventional C41 process that uses separate bleach and fix solutions. This is for comparative purposes because I can pretty much guarantee that there will be at least a small amount of residual silver in the film regardless of what method is used for bleaching and fixing. Therefore, a comparative analysis is the only one that would be meaningful.
The scheme above would definitively settle the question of how much silver would be left in the film, and if NAA is used it would also answer how much bromine, iodine, and chlorine is left in the film. It would not answer questions about color shifts or longevity.
Optical spectroscopy of processed film could answer questions about color shifts. Unlike the schemes mentioned above, the optical spectroscopy experiments could be performed at home by anyone having a spectrophotometer capable of light transmission measurements, such as the type of spectrophotometers used for color management. A number of photrio members have one of those instruments, including me. Even a colorimeter, film scanner, or flatbed scanner would work well enough for determining relative color shifts. Longevity determinations are another matter altogether.
Realistically, I don't see any prospect of anyone here doing the measurements noted above, except for color the shift measurements. Consequently, as far as current products are concerned, we are reduced to arguing with each other based anecdotes combined with speculation.
Hi PE,The test not present in using control strips is granularity. This may be the only definitive test, but there are others that might work such as spectrophotometry.
The only "blixes" I saw that worked were two:
A rehal Ferricyanide/bromide/hypo blix that was one-shot. It went fast. And the second was the FeEDTA/Ammonium Thiocyanate type in our patent US 3706561.
As such, Kodak was unable to get a blix to satisfy their needs and thus the bleach then fix as we now know it was used. To further extend the argument though, Fuji does NOT use a blix either.
PE
Alan if you have the ability to create an other competend test in concern of long live I would be interested!
The one Kodak made was obviously from normal budget Kodak spent at this time! (Years ago)!
But some doubts in regards of scientific seriousness may be " allowed " because Kodak came
at 200 years (E6)......that sounds in comparison of K14 (175 years) a bit strange!
But it is illusioness to prove it : Do you have 350.000$ for a smallest prove of Kodaks result concerning long time color stabitity! And that would not be in concern of Blix !
with regards
(the 200 years for E6 is an abstract value in regard of specific determinated storage conditions)
So no fearyour slide films will N O T hold colors as long!
But K14 Films (without projection) will be more stable (Kodak was determining a value of projection time for E6 and K14 what gave E6 an massive advantage!
Thanks for the additional comments.Alan, the second example of our patent was preferred. But, it too lacked some degree of stability. You see, these chemicals are expensive and Kodak tasked us with low cost as well as good shelf life and tank life, and that was a problem with anything with an oxidant and hypo.
Chemistry aside, the competing blix formulas and patents all had problems of one sort or another, including the fact that if there was no excess EDTA, Ferric and Ferrous salts would precipitate out in the coating, and this led me of in a tangent to my work with Dequest (unpublished) which removed the Iron salt stains.
In the end, Kodak management did not feel that we had met the time goal for a formula and the cost goal for a blix, but had exceeded shelf life goals and open tank goals. They decided not to use it, but as noted above have recently added Thiocyanate to the fix and used a stronger oxidant in the bleach.
Yes, the data is very old, and the changes noted above reflect the changes to the current C41 process. They have reaped a small increase in bleach and fix rate.
PE
And the simple solution of just adding some excess EDTA was off-limits for Kodak, since there was already patent GB991412A which covered just that.Chemistry aside, the competing blix formulas and patents all had problems of one sort or another, including the fact that if there was no excess EDTA, Ferric and Ferrous salts would precipitate out in the coating, and this led me of in a tangent to my work with Dequest (unpublished) which removed the Iron salt stains.
Let me take a day or two to digest what you just wrote. However, just for clarity, are you sure you mean NH4? NH3 is a good ligand, but NH4 (I think you probably mean NH4+, since NH4 is not a stable molecule) is not a good ligand because it does not have a free electron pair to act as an electron pair donor for the ligand formation, whereas NH3 does have a free electron pair and is known to be a good ligand.Alan, sorry I did not answer your comment about Ligands, but it was late and I wanted to have a way to explain this area in a reply.
It is best, IMHO, to refer to NH4, SCN, Hypo (S2O3) and EDTA/PDTA/NTA as complexing agents as they can complex with metals in these situations. The metals include Fe+3, Fe+2 and Ag+. Complexation of Iron takes place at just about any pH with EDTA, NTA and PDTA, but the oxidation potential varies being far far stronger at more acidic pH values. These have multiple charges and sites for complexing. They can form both salts and complexes. Use of Ammonium ion adds another plus charge, and another pair of electrons and so you may say that NH4Fe(+3)EDTA is electrically balanced with 4+ and 4- charges. NTA is not balanced this way.
Hypo and SCN do not act with Iron to complex it in any meaningful way but can form "salts". NH4 does complex strongly with Iron salts. Silver OTOH does not complex meaningfully with EDTA, PDTA or NTA, but does complex with Hypo, SCN and NH4. These complexes are far more stable over a wide pH range than the Iron complexes but the rate of formation varies widely.
Silver can form as many as 5 complexes with Hypo itself, whereas Iron only forms one complex with EDTA as an example. I don't think it is known how many complexes Silver can form with SCN. As far as internal Kodak documents, we never found any studies.
PE
AFAIK Ferric Ammonium Sulfate is a mixed salt, not a complex. Also, as pH goes up, there will be a noticable supply of free Ammonia.Rudi, in water we can just refer to it as NH4+ or Ammonium ion. It does form a complex with Iron as in Ferric Ammonium Sulfate.
Logarithmic complex stability constant of EDTA and DTPA with silver are 7.32 and 8.70, respectively (NH3: 6.8). Obviously the complex of Ferric ion and EDTA/DTPA is much tighter (25.10 and 28.60), so FeCl3 will displace EDTA/DTPA bound silver ions at once. Since working bleaches have an excess of EDTA, there will be some uncomplexed EDTA in solution. However, the main competition for silver comes from Bromide (bleach) and Thiosulfate ions (BLIX), so I would not expect much Ag-EDTA.Under the conditions we are discussing here, Silver does not form a complex with EDTA/PDTA/NTA. A mix of AgNO3 and these complexing agents shows little complex formation as well. Add some FeCl3 and you see a complex form with Iron, the instant it is added.
Stability constants are somewhat equal, however, it is much easier to get multiple moles/liter of Ammonia dissolved in water, so I guess that's where Ammonia tips the balance.In an alkaline solution of AgNO3, you can dissolve the hydroxide formed by creating an Ammonium complex, but you cannot do this easily, if at all, with EDTA.
Rudi, Silver can be left behind in film when a blix is used. I know, I have run the Silver analyses and also checked grain and color. Colors are muted due to addition of a neutral density (Silver metal) and grain is up.
PE
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