Topic: FomaPan question

[astrobeck]

this may be a bit silly, but what exactly is the green dye that washes out of the rinse water during development of FomaPan?
Is it just dye, does it affect the pH of the mixture?
After developing this stuff for many years, even in the Arista version, I have this question.
Is it actually changing the developer if I don't rinse/soak first, which I sometimes don't do.

It's quite an impressive colour green too.

thanks!
B

[Bryan]

It shouldn't affect the chemistry, it's just an anti-halation layer on the back of the film.  It's designed to wash off during development.  If you're doing a pre-rinse, it may come off at that point.  Some films don't have it and it's different colors on other films.  From what I understand, it prevents light from reflecting off the pressure plate back onto the film.   

[Francois]

Yep, anti halation.
It's there to prevent the blooming highlights.
Luckily on the Foma, it comes off quite easily.
T-Max's dyes are much more stubborn and require extended washing times.
But they're all designed to be safe for chemistry.

Also, some chemicals are probably better at stripping the stuff out than others.

[Kai-san]

I always do a pre-wash of all B&W films; fill the tank with water that holds the same temperature as your developer and let it sit for 5 minutes before you dump it. When I do this with T-Max the pink colour disappears. Besides the pink T-Max I've seen films with yellow, green, black and blue anti-halation chemicals. Some people say that a pre-wash gives better developing results, but I have not done any tests to check it out.

[Indofunk]

I always do a pre-wash of all B&W films; fill the tank with water that holds the same temperature as your developer and let it sit for 5 minutes before you dump it. When I do this with T-Max the pink colour disappears. Besides the pink T-Max I've seen films with yellow, green, black and blue anti-halation chemicals. Some people say that a pre-wash gives better developing results, but I have not done any tests to check it out.

I've seen purple too. Maybe it was the time I developed Ilford XP2 in B&W chems?

[Francois]

Some people say that a pre-wash gives better developing results, but I have not done any tests to check it out.

It does, especially when using short development times.
Pre-soaking allows the emulsion to swell-up completely so that the chems penetrate the layers evenly.
Also, it buffers a bit so that the chemicals slowly start to develop (they get slightly diluted at the start) and makes the emulsion get to the proper temperature before starting.
That's why you have to do that with C-41.