Photo-Flo substitute?

The nonesense continues...

Photo Engineer said:

You see, when a gelatin is hardened, fewer sites for cross linking are left behind so formalin reacts with one strand of gelatin rather than cross linking to two strands. The singly linked formalin is easily split off and releases with time giving a small but real presence of formaldehyde in the coating. So, over time you have the free formalin which kills the initial bugs present in the process solutions (if any), those that land on the film during drying and storage (if any) and those introduced by handling (if any). (This slow release of formalin can be measured and takes place with any material that contains formalin including clothing, finished wood and leather. The slow release of formalin in the household is what can cause problems with color films as the formalin can infiltrate the film container and react with the couplers.)

Click to expand...

Ron, do you know how many sites of primary amino residues are present in a gram of gelatin? And do you know how much hardener is actually reacted to harden the gelatin? So what's the fraction of amines that are consumed by hardening in film manufacturing and what's the remainder? You are playing with words not the actual meaning of what the crosslinking is.

It is true that the bond between formaldehyde and gelatin is easily reversible and not as strong as in the case of gluataldehyde, but the concentration of formaldehyde present in the final rinse bath is way too low in order for your argument to be meaningful in this context.

As I said above, benzoic acid is ineffective as a fungicide.

We also know that you often switch the point to vague ones, such as "experience at Eastman Kodak" and such, but I must say that your statement of using formaldehyde and benzoate as biocides in dry film is not very well thought out and has many flaws as I pointed out above. And it is hardly original. Tetenal makes a product called Mirasol 2000, which incorporates isothiazolinone biocide in addition to Triton X-100 surfactant. Whether isothiazolinone is very effective against fungi and mold is another issue, but at least nonchlorinated alkyl isothiazolinones are a better choice for this application.

Ryuji;

As I said, the difference between what you say and I say is in theory vs practice. You have read this all in books, but I not only have studied many of the things you have, I have carried them out in practice.

In theory, there are lots of sites left to 'crosslink' but they are made difficult, in practice, for formalin to complete reacting with by either the swell of gelatin when wet carrying them too far apart for formalin to 'reach across' or making the matrix too stiff when dry for formalin to 'reach across'. Either way, you get formalin only partially reacted with the gelatin and liable to release on keeping.

So, in practice, you would observe an unexpectedly large quantity of free formalin in film over an unexpectedly long time and the studies I have seen bear it out.

Benzoic acid has been proven to protect photographic materials from attack by 'bugs' by acting as a biocide. It was used for years in color paper stabilzers, and was tried in film stabilzers and final rinses but never released.

In any event, the formalin bath will still serve to sterilize the film before storage, during drydown, and any trapped formalin will degas from the film slowly with time.

It may interest you to know that the current E6 and RA paper stabilizers use a proprietary isothiazoline in them. It is hardly new. The interesting thing about this is that when EK and Fuji fixed the color film problems that required formalin, they replaced the formalin in the final rinse with a biocide.

This is the final culmination and proof of the effectiveness of formalin and the proof in fact of what I have been saying here! Get rid of formalin in processes that use it, and you need a biocide. Therefore, formalin was acting as a biocide.

Before others point out the obvious, that is, why only use it in color processes. I can answer that as well. Color materials needed formalin for dye stability and as a biocide both. They needed it as a biocide due to the thicker gelatin layers and the higher organic content. B&W products were deemed less prone to attack by 'bugs' due to being thinner, containing silver (a natural biocide to some extent so to speak - silver nitrate was used as an anticeptic for years) and the lower gelatin content compared to synthetic materials. EK and other manufacturers apparently did not want to use formalin unless absolutely necessary.

PE

Photo Engineer said:

As I said, the difference between what you say and I say is in theory vs practice. You have read this all in books, but I not only have studied many of the things you have, I have carried them out in practice.

Click to expand...

Ron,

...

Some of what you wrote are outright incorrect. Aldehyde hardeners crosslink gelatin more rapidly and efficiently when the gelatin is more concentrated or dry, when they come in contact, exactly because the average distance between available amino goups is shortened. Your story of aldehyde being less efficient in crosslinking when gelatin is dry because they have difficulty in getting into gelatin matrix is only laughable.

Also, the reason why biocide is sometimes used in final rinse is because the final rinse water is reused for a long time in processing machine after London dumping convention came in effect. The final rinse water is reused over and over by removing thiosulfate and other chemicals by resin or other means. Bacterial growth is a common problem in this part of the processing machine. When color material is processed in conventional small tank or dish method, manufacturers no longer require a special final rinse bath because of increased stability of the dye formed by modern couplers.

These are just two points showing how your arguments are flawed.

sanking said:

Can someone recommend a substitute for Photo-Flo that can be mixed up with things that many darkroom enthusiasts might have on hand, or pick up at the grocery store?

Sandy

Click to expand...

Well you can't pick it up at a grocery store but I am partial to Edwal LFN. The dropper and minute quantities needed is very convenient and makes one-time use seem less wasteful.

Sincerely,

Hany.

Ryuji;

The C41 process, in spite of the convention you cite is still available with formalin in its dual role as both a stabilzer (for older films) and biocide. But you miss the logic of the need for a biocide and the fact that formalin acted in a dual role. If it was not a typo, you even believe that the dye stabilization role of formalin is due to reaction with dyes as you stated above. Formalin is not reacting with dyes, only with couplers to form the methylene bis coupler. It also acts as a biocide and the newer stabilzers have replaced formalin with just the biocide function.

The full crosslinking action of formalin is limited if the number of sites is reduced by the presence of other hardners introduced at the time of manufacture. It is also limited by the flexibility of the gelatin, the swell of the gelatin and etc. You are not entilrely correct (see below), when you say that gelatin reacts with formalin rapidly when dry. That statement only holds somewhat, and then only if the formalin is added during coating, but must be mitigated by the fact that we are talking about coatings already hardened and then treated during the process with formalin. This is a different case.

There is a condition called after-hardening observed in formalin hardened coatings where the formalin hardening continues for several months to a year after coating. This argues for the theory that formalin is still present in coatings after one year. Analysis shows this is correct. Early type "C" and type "R" papers used formalin hardening and showed changes over years due to after hardening by formalin wich only partially crosslinked and continued to link gelatin over time if not refrigerated. This is one reason why early color papers required refrigeration. Some B&W and color papers also showed fog due to the presence of formalin up to a year or more after coating. This is one reason why the new hardeners gave better keeping. (a fact you seem to ignore readily in the above arguments)

Now, I feel that you are not writing science fiction, but you are limited in your actual practice of photographic engineering. Your theory is just fine. OTOH, I feel that you lack practical experience and are attacking me personally. We could both benefit if you ceased these attacks and discussed things without this anger that you display. We both know things that the other could benefit from. I have tried to illustrate for you some of the things that you may never have heard of before, but you consider it to be fiction. Well, I assure you it is fact.

If you cannot get around your anger and hostility we will never be able to communicate and benefit the other members of APUG. This is not a seemly interaction between professionals.

I apologize again to other APUG members. My intent was to put forth some additional post process treatments for film and paper to point directions for improved image stability, but I guess our resident "expert" has decided that I'm totally off base or worse. In the interests of the other members, I am terminating my responses to this thread. If you wish more information send me a PM or e-mail. Many thanks to those who have already messaged me.

PE

Decades ago, far from camera stores, I had access to a wetting agent trademarked Aerosol. We diluted it in trichloroethane for cleaning big Ampex tape recorders. Diluted in water it seemed to work much like Photoflo on film. An old Photo-Lab-Index recommends a .1% dilution, which isn't critical. I'm satisfied with Photo-Flo. Since one bottle lasts a very long time, I see little reason for most of us to use substitutes.

Dear all;

I hate to ressurect an old topic, but when I am told I am not correct, I try to correct the situation. To do this, I hit the books to look for references.

In this case, I have found information in Mees, Mees and James and Haist that support the position that formaldehyde in coatings lingers for up to a year or more in coatings in their dry state. In addition, I find that silver and its salts is a powerful biocide. It does not react immediately either during coating or during stabilization.

Therefore, B&W films with silver in them require no formalin in the process and can maintain gelatin integrety for years due to the 'support' of silver in eliminating attack by bacteria, mold, and fungus. Color flim cannot, due to the removal of silver and therefore rely on formalin or other biocides to keep them clear of attack by biological agents.

Hardening in films or papers with formalin or other aldehydes does continue for several years due to the action of residual hardener (formain) and contributes to loss of speed, loss of contrast, and increase in fog of the raw stock.

This information is all in the references above and also derived from personal experience.

PE

Many metals are biocides, which is why ships have used various metals over the years to inhibit biological growth. Silver has not been used in the marine environment for obviou$$ reasons, but I seem to recall some medical applications. Is there a doctor (MD) in the house?

DBP said:

Many metals are biocides, which is why ships have used various metals over the years to inhibit biological growth. Silver has not been used in the marine environment for obviou$$ reasons, but I seem to recall some medical applications. Is there a doctor (MD) in the house?

Click to expand...

In the early 20th century, silver nitrate was an anticeptic of choice for many occasions.

PE

Until quite recently, silver nitrate drops were placed in the eyes of the newborn to avoid infection. Largely replaced with other antibiotics today. I expect anyone old enough to be reading this board, born in the US in a hospital, had silver nitrate administered.
see http://www.nlm.nih.gov/medlineplus/ency/article/001606.htm for more info.
Bart

I do use a product called "Drywell" by Fuji, but I don't really need it because everytime I print, I clean the neg with a film cleaner and put a fair amount of nose oil on it.

that´s the way to go, i heard that oil nose will improve acutance, reduce grain, correct distortion, and even cut flare

firecracker said:

I do use a product called "Drywell" by Fuji, but I don't really need it because everytime I print, I clean the neg with a film cleaner and put a fair amount of nose oil on it.

Click to expand...

??? from inside or outside the nose???

You would think we could have a civilized discussion about Photo-Flo, though now that I look more closely, it seems the abusive posts were from 2006, so maybe we can just avoid resurrecting this dispute at the moment.

J Marion Sims successfully used silver wire suture to repair vesico-vaginal fistulae in 1852. Silk, cotton or flax would cause breakdown of the repair in the absence of surgical sterility.