The definitive word (I hope) on color stabilzers!
I have gotten quite a few queries regarding color stabilizers and have therefore undertaken a project investigating them and trying to clarify them in one post.
Cyan and Magenta couplers react with their respective dyes causing brown stains and loss of dye. This makes a print, slide or negative turn red or green with a brownish border or light areas that brown up. In addition, color materials have all of the silver removed during processing, and since silver is a biostat killing microorganisms, color materials can be "eaten by bugs".
Traditionally, formaldehyde was used to combat both problems. Formalin (Formaldehyde gas in solutions) was the answer. E6, E4, C41 and C22 processes for film used this and Ektaprint C and Ektaprint 3 used it as well.
Formalin reacted with the left over coupler and also the gelatin to form substances that resisted both coupler induced degradation and the bug attacks. But, it was found to be harmful to humans doing the processing (and perhaps afterwards). Now, formalin is used in the sizing of new clothing and in the finish of new furniture, but that did not matter to those who safeguard our health by force! So, Kodak undertook a project to eliminate the formalin from all stabilizers (Film and paper)
In the 60s, a paper stabilizer was citric acid at pH 4.5 with benzoic acid and sorbitol + formalin. A film stabilizer was formalin + Photo Flo 200 or the equivalent. When E6 and C41 rolled around, they kept the same stabilizer but paper eliminated the stabilizer by incorporating some of the stabilizing agents into the paper itself. So, C22 stab = C41 stab = E6 stab = E4 stab at about 1970. Remember this!!!!
Along the way, the "people who control us all" decided that formalin must go. Well, a coupler R&D program is expensive but a process R&D project is not so expensive, so the product with the most "weight" in sales got the biggest R&D share. That was C-41. A new family of couplers was introduced around 2000 and this family of couplers no longer needed Formalin. It was exclusive to C41. E6 OTOH, used the old couplers and embedded formalin in a bleach pre-bath that imbibed in a harmless version of formalin which was activated during processing.
So, we now have 4 stabilzers/final rinses.
Stabilzers C41 = E6 (pre about 2000) which contain formalin.
Final rinses (C41) which is a biocide and the functional equivalent of Photo Flo 200 only and E6 which requires a formalin precursor and a biocide and also both an anionic (I think) and non-ionic surfactant (that good old Photo Flo 200 again). The current E6 final rinse has a new ingredient which looks like an anionic surfactant. That is all I can say at this time.
Older E6 and C41 Stabilizers can be used for all films but the modern versions cannot be used with early films (pre ~2000) or must be used with a pre-bleach such as used in E6 to release formalin during bleaching. The E6 bleach is designed to do so.
Anyhow, the oldest expiration date that I can find on Stabilizer III for C41 is about 2003 so that kind of dates this solution. After that, a final rinse was used for C41.
At the present time an RA4 final rinse is also made. It is intended for processes with low or no wash and IMHO is courting disaster.
What does this mean? ALL C41 films made before about 2000 and all E6 films need formalin in sole form or another. Leave it out and your negatives and slides will turn green or red and may show a brown stain. If your process for these films does not contain formalin you will have problems in months, days or years. I cannot predict the failure rate. E6 processes without formalin or a pre-bleach bath will cause eventual problems whatever the date the films were made.
This applies (apparently) to both Fuji and Kodak products.
This does not address motion picture films and I would ask that this subject no be brought up in subsequent posts. Thanks.
How to make a formalin stabilzer? Easy!
Mix up Photo Flo 200 as directed on the bottle. To one liter of this add 3 - 10 ml of 37% Formalin solution. That is it. The reason for the spread is that I have found several formulas with values like that. I use 10 ml to be on the safe side.
Oh, and this type of fade is dependent on density and therefore is non-linear. It cannot be corrected by filtration or in Photo Shop scans. Sorry.