Composition of film Anti-Halation Layer

[Raphael]

Hello All,

I am concerned about all the chemical effluents I throw in environment when I do lab (B&W, for the moment), and as many, I take care of bringing all my used chemical to a local collecting place, as hazardous (!) wastes.

Since a few months, I use often pre-soak for film or sheet-film, and in consequence produce heavily colored water. I collect and treat them exactly as the rest (and bringing them to the collecting place).

Do you think this is overkill ? What's exactly in film anti-halation layer ?

Regards to all,

Raphael


P.S : BTW, I saw something funny on a flask of these AHL colored water : on sunlight, water appears deep violet, and when changing light incidence, green reflections appeared, a kind of metamerism, I presume ? I guess this is certainly have to do with the properties needed for anti-halation, but I haven't noticed it before. :rolleyes:

 

[jp80874]

Raphael,
I believe this is a personal decision based on your views and your local laws. Disposal of chemicals, the law, ethics, septic systems, and city sewage systems have been discussed both here and the LF Forum. My understanding of what has been written is that the only chemical dangerous to the environment is the fixer. Everything else can be safely thrown out with the waste water.

In my own case, living in a rural area, using a septic system and a well, I send everything but the fixer through the septic system. The university where I take photo courses encourages photographic students with home darkrooms to bring in their fixer for proper disposal. They see this as a gesture toward a clean environment. Some may claim that they do this for the value of the reclaimed silver. They say it is only pennies or of little value. When I do not have access to the university I use a five gallon bucket with steel wool to leach out the silver. The liquid is then safe to dump. The steel wool is a small mass and can then go to safe garbage disposal.

I would encourage you to search both forums for further details and other opinions.

John Powers

 

[Raphael]

Hi John,

I am agree this a subject (dump sink or not) heavily disputed here, and my aim is not to start another discussion of this subject in his whole domain, and I believe that such subject can easily degenerate in flame war

I just want to focalize on the AH layer product, and want know the composition of the thing, if possible. If the AH layer is not more than, say, beet juice, it confirm me that I'd better dump it in the sink

Regards,

Raphael

 

[Photo Engineer]

The dyes that wash out are water soluable azo compounds akin to food dyes. One early dye used was Tartrazine, a yellow dye and another was an Oxonol dye.

But, that said, you must realize that minute quantities of sensitizing dyes wash out with the process when the emulsion is developed and fixed. These are complex organic dyes unrelated to the azo dyes mentioned above. However, they are present in such tiny quantities that they would go undetected except by very sensitive tests. Usually, they decompose rapidly on contact with sunlight.

PE

 

[AgX]

When trying to upload my reply I just realized that PE has given the answer already. But As I’ve written my reply already, I’ll send it anyway…


A simple answer would be hard to gice I guess, as many dyes could be used.
Most probably the kind of dye you are referring to belongs to the group of oxonols (if that would of any help to you), but I’m still guessing.

The initial task of the Antihalation-Layer is, as indicated in its name, to reduce backscatter from the film base. Especially repeated reflection from its back surface. The more distant that is, the larger in diameter its effect on emulsion could be.
To deal just with this would be sufficient if the film would be loaded in a darkroom into cassettes (like with sheet films, or with aero films).
But in any other case there would be the chance that light enters the film base via a the naked back, or even with a coated back via the edges (lightpiping)
Remedies:
Layer between emulsion and base
Dyed base
Backlayer on base
Sometimes both issues are coped with by employing one feature such such as a permanently dyed base.

If you restrict to the first scenario, a light absorber is brought in with a special AH layer between the actual emulsion and the base.
Used absorbers:
-) colloidal black silver (also used in a yellow configuration for a yellow filter) and bleached out in processes which contain a bleach.
-) a soluble dye (which could mean soluble in water or one of the processing chemicals.

Furthermore a (soluble?) dye can be used within the proper emulsion to reduce scatter.

 

[Raphael]

I secretly hoped that very knowledgeable persons, like PE and AgX, was so good as to answer my question, and I am now granted

Your answers are complementary, thanks to you both.

Regards,

Raphael