Stop Bath.. How important?

Don_ih · Wednesday at 6:33 PM

Photodegree said:
Stop bath is an absolute requirement.

Go read the preceding 1300 comments. It's not a requirement for film at all and it's only marginally beneficial for rc paper. It's a "requirement" for fb paper - particularly porous fb paper (like Ilford Art).

koraks · Thursday at 3:02 AM

Photodegree said:
Basically the change in pH from base to acid literally squeezes all the developer out of the emulsion. This means the stop bath not only neutralizes the developer it rids the emulsion of the chemical as well, to make room in the emulsion to absorb your fixer.

Welcome to Photrio! There's some merit to this very simple and clear way of putting it. It also aligns well with what @Photo Engineer (RIP) said in the past about ECN2 stop bath needing to be very acidic for this specific reason.
Whether stop bath is an 'absolute requirement' - well, we've not quite been able to figure that one out in 20 years. Let's see how we stand on the matter by 2045.

Augustus Caesar · Thursday at 9:55 PM

IOWA CAMERA GUY said:
"On the long edges of each frame is a subtle area of increased density which runs the length of the frame. "

It's very hard to say definitively. There can be some excess density added around the sprocket holes with over-agitation. The developer slows in handout through the sprocket holes more than across the rest of the film.

STOP BATH VS WATER: This is pretty obvious, but here goes: Stop bath "stops" the developer action with a chemical reaction which is essentially instantaneous. Think baking soda and vinegar, instant action, also bubbles formed by the chemical reaction. If the acid-base reaction is strong enough - you put in too much stop bath (too strong), then bubbles can form and pop the emulsion right off the film base. I've used plain developer temp water, which stops the development by dilution, fill, shake, dump, and you are probably OK but if you want, do a second fill, shake, dump, just a few seconds is all you need.

Someboddy's gonna take exception to this, probably, but I've been processing film since the mid-1960's and owned a camera store which did enormous amounts of processing of all sorts, including a well-equipped b/w darkroom operation, that's how we did it, nearly fool proof.

***** I received the info from a friend, and assumed it was 'current'. Joke's on me, I guess. OH well, no matter, answer's still the same. Thanks for pointing out my delayed response. -)

BTW: It would be good to see a sample of what the problem looks like, that may help more than 1000 lines of text in reply.

Yes. Use stop bath!

grain elevator · 2025-08-15T05:16:17-0400

Photodegree said:
Stop bath is an absolute requirement. Basically the change in pH from base to acid literally squeezes all the developer out of the emulsion. This means the stop bath not only neutralizes the developer it rids the emulsion of the chemical as well, to make room in the emulsion to absorb your fixer.

Can you elaborate please? I can't imagine how this works

MattKing · 2025-08-15T12:33:09-0400

If you are running film high speed through something like a roller processor, and process times are closely controlled and really short, something like stop bath is critical. For hand processing, there are other effective choices for film.
I use stop bath.

Stop Bath.. How important?

Don_ih

koraks

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Augustus Caesar

grain elevator

MattKing

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Stop Bath.. How important?

Don_ih

koraks

Moderator

Augustus Caesar

grain elevator

MattKing

Moderator

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