Blix question for Photo Engineer and others
Even though blix is generally considered inferior to separate bleach and fix, I am wondering if you could use blix successfully (i.e. producing high quality) in the following way: 1) mix immediately before processing, and 2) use only in one shot mode.
Alan, I've used only Blix for the past 25+ years for C41, RA4 and E6 with absolutely no problems, as long as I followed the manufacturers instructions. I almost always used the (Johsons) Photocolor Kits, later sold by Paterson.
The ONLY time I had a slight problem was when I deliberately tried to exceed the manufacturers re-use recommendations, and a quick dunk in fresh Blix cleared up the problem of residual silver.
Ron (PE) has his own opinions on Blix, but all I can say is I've never heard of any problems using Photocolors Blix for C41 films colour or B&W - XP1/XP2.
Blix keeps reasonably well so no need to make up fresh each time, but a good shaking in a half filled bottle helps before use. Unfortunately Photocolor products are not currently manufactured.
Well, I have done analytical examination of the films processed in blix looking at retained silver, retained silver halide, grain, contrast and color reproduction and they all were inferior.
Here is a good reason. Lets say your bleach has 100 grams / liter of Ferric EDTA, and your fix has 100 grams / liter of Ammonium Hypo. Each works well. If you mix those to get 2 liters of blix, the concentration is now 1/2 of each ingredient, and they work less efficiently that way. So, you would have to mix the bleach to 1/2 liter and fix to 1/2 liter to get 1 liter of Blix, and that is sometimes impossible as the concentrate is already 1/2 liter in some cases, so you might be adding no water.
Then again, shaking a blix will certainly oxidize the Ferrous EDTA back to its original state as Ferric EDTA, but at the same time you oxidize the sulfite and the hypo.
In a blix, the sulfite is oxidized fast enough and is needed to remove color developer and is critical due to the blix being an oxidant. If you don't remove the CD fast enough you get colored stains.
Last but not least, a true blix must penetrate thick layers in film, 'scrub' grains of the inhibitors and it must remove 100% of the silver as metal in E6 films, as this process goes to completion. Therefore E6 and C41 films differ due to the balance of silver/silver halide remaining in the film. The blixes are interchangable, but you have to alter the times.
I have designed a film blix while at EK, but they judged it to be too expensive, and went with a concentrated bleach then fix after a panel reviewed all data. Our blix was second runner, and all other blixes failed in the judgment of the panel due to severe problems with the final processed film.
Now, I always say "do what works" and I respect Ian Grant's expertise, but I would wager that if he did some quantitative analyses on films processed both ways, he might change his mind. OTOH, he might accept the decrease in quality as within tolerable limits and he might feel that Kodak (and Fuji and Agfa for that matter) were being overly cautious.
I would go with the consensus of the 3 major manufacturers of color films. If it were not a problem, then we would have had a blix from one of them and a big AD campaign about the "new, shorter, better process". See my point?
In any event, I'm working on a true film blix usable for both C41 and E6 films based on my patent, but improved with what I have learned since those days. IDK if I will ever truly achieve perfection, but I'm still trying.
I've said it before Ron, the late Pip Pippard, the Johnsons photochemist was an acknowledged expert in B&W Colour processing chemistry and his Photocolor II C41 & Chrome 6 E6 kits were always thought to be the best independent colour chemistry available for small scale use.
Originally Posted by Photo Engineer
Pippards kits including the Blix's were well tried and tested when they were first released against the manufacturers own chemistry, and always highly praised for giving indistinguishable results to lab processed films.
So in saying you can design a Blix that works, you are also saying it can be done. I have used other Blix's for C41 films and don't trust them, they aren't as fast or as good as Pippards formulae. This is why I don't ever recommend other C41 or E6 chemistry that I haven't tried and have full faith in.
What about color negative paper processing? Usually RA-4 (and the old EP-2) use blix, including Kodak and any other brand I know of.
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The silver content of colour paper is far lower than film and Blixes work far better, also and very slight traces of residual silver would have no real or apparent effect.
Yes - I'm also curious as to why Blix works for RA-4, but not for film. Are there any advantages to doing a bleach followed by a fix stage for RA-4? For the Kodak RA-4 Blix, could I choose to not mix parts A and B and separate the Blix step into a Bleach followed by a fix step? I assume part B is the bleach and part A is the fix.
Originally Posted by fdisilvestro
Paper has about 100 - 200 mg / ft square of AgCl/I emulsion in it with no severe restrainers. There are 6 layers and they are very thin. The iodide level is probably less than 1% in current papers. The grains are about 0.2 microns.
C41 films contain in the range of 300 - 400 mg/ft square of AgBr/I emulsion with heavy restrainers called DIR couplers. The films have up to 14 layers. Iodide ranges up to 10% in grains up to 10 microns.
In film, the packing of coupler around silver halide results in a tight package of dye which forms when the silver halide grain develops, and as a result the dye cloud also insulates the silver and silver halide from the blix. In paper, the same is not true. This difference is due to the need for fine grain in film which is not so pressing in paper. In reversal, you have dye clouds packing silver on silver in higher density areas.
These differences makes it possible to blix paper to completion but not film. Even so, with any blix or even a ferricyanide bleach then fix, paper or film would retain up to about 1 or 2 mg /ft square of silver as silver sulfides and silver iodides which don't bleach or fix easily.
The result of retained silver in film, which can run high, such as > 50 mg/ft square, will result in a dark mask that obscures the color dye, and also a slight distortion of color if the silver is colored. It also adds a very slight patterning, or grain, that results from the combination of dye clouds and silver grain. Sometimes it is bad, and sometimes it is neutral to the image quality. There can also be degradation in sharpness.
In reversal products, where you have a combination of silver from a B&W developer and a color developer, you have 2 kinds of silver to bleach out and then fix. Essentially, since it goes to completion the bleach part has the heavier load as there is 100% silver development in Dmin areas. With a poor blix you can get veiled highlights or a yellow dmin when a blix is used in an E6 process.
We ran quantitative tests on retention plotted against factors such as dye purity, grain, sharpness and etc... The panels viewing the prints in blind tests judged the blix processes, the best we could make, to be inadequate except for the Ferric EDTA version that was eventually patented. It was rejected due to cost and to the fact that it was too late in the development cycle of the C41 process.
The current RA blix is based on a paper formula finished in October 1966, and was designed to avoid use of any currently in-force patents. It was the only blix approved by Kodak.
The red part is Ferric EDTA + Sodium or Ammonium EDTA, and the clear part is Sodium or Ammonium Sulfite + Sodium or Ammonium EDTA + Sodium or Ammonium Thiosulfate. The final pH is between 6.3 and 6.7 at 20 deg C.
I should add that Kodak is changing to NTA from EDTA in some products, and Kodak blixes and bleaches and fixes are all comprised of ammonium salts for greater effectiveness.
This cannot be said of some of the other products on the market.
Also, as I noted above, the guys at Fuji and Agfa must have agreed with the Kodak opinion that a bleach then fix was best or we would have seen an ad campaign for a new and improved process from one of them.
Also, powder blixes and bleach then fixes are generally less effective than liquid kits due to the need for using sodium salts rather than ammonium salts.
In addition, the patent for making Ammonium Ferric EDTA was a Kodak patent until it expired. All current ~60% solutions of Ammonium Ferric EDTA were made using the Kodak method AFAIK. Kodak originally made it in their own labs for product.
Well, here are some other items that I just thought of that should be in the above posts.
Any bleach, fix or blix must be designed for the most resistant product that will go through it. So, for example, a 160 speed negative color film is easier to bleach or fix when compared to an 800 speed film and therefore people will see variable results when reporting if they use different films.
Black and white C41 films are even easier to bleach and fix than any color film. In this case, you will observe a contrast increase in most cases and a change in grain. With color C41 films, with a blix, you often see nothing more than a contrast increase and a muting of colors.
A way to demonstrate this to yourself is to shoot two identical shots and process one normally and use bleach bypass on the other (no bleach just fix). This represents the two extremes that you can observe. The real blixes will fall somewhere in between. The actual appearance will vary with film type and blix brand.