Stop Using Stop? - Pinhole Frustrations

[Ranger Bob]

I haven't used acid stop for film since art school 10 years ago. Had a few pinholes on an important roll, talked to some of my photographer friends in Colorado Springs, said use plain water, three changes with agitation for 30 secs and have never had a problem since. I do use acid stop for paper though. Does my info count since I had been making photographs for 10 years before that and quit art school after 3 semesters?

 

[Photo Engineer]

I have been using an acid stop for over 50 years!

Never saw a pinhole from an acid stop!

Saw pinholes for other reasons.

PE

 

[Ranger Bob]

I'll be quiet now...

 

[dancqu]

Dan; Just FYI, the diffusion of the hydrogen
ion (the smallest ion of them all) is rapid.
That is why a stop is fast! PE

I've given that some thought.
First I do not believe an electric field of any
extent can exist across such a permeable
medium as an emulsion in solution. That
is, migration of positively charged ions
is very little ahead of any negative
ions. And that at an atomic scale.

Second, the usual acid stop is 98% or 49
parts H20 and 1 part acetic acid. Dan

 

[Photo Engineer]

Dan;

The film is alkaline at about pH 9 in dmin regions and about pH 7 or less at dmax. The diffusion gradidient of hydrogen ion is driven by the pH gradient and through a gelatin lattice is rather rapid.

It depends on developer, development rate, and film.

Generally, diffusion of the whole content of a solution is complete within 15" which is normally considered the minimum time of full wetting of a dry emulsion. Hydrogen ion can move faster than that, usually taking on the order of 5 - 10 seconds in a wetted film or paper.

PE