RE: Adjacency Effects Again

There is a discussion of adjacency effects in the
"theory of the photographic process" by Mees & James.
A very brief summary:

- manifest adjacency effects are usually directional, and can be
  exesperating.
- adjacency effects are supressed by strong agitation
- "Hansson" found that they tend to be small for active,
  concentrated developers and for a high bromide concentration
- they can arise during washing because the bromide diffuses away
  rapidly in the wash water relative to the developer,
  which continues to act without the restraint of the bromide
  -> this is prevented by using a stop bath
- they decrease as development time increase and disapear with
  full development

There is also some information in the book "Image clarity" and
the indeed state:

"Adjacency developers are necessarily Metol based. Phenidone is not
restrained significantly by bromides. Hydroquinone is
affected only by large quantity of bromides."

But maybe pyro is similar to metol in that respect?

gregory

> -----Original Message-----
> From: Sandy King [mailto:sanking@clemson.edu]
> Sent: Friday, April 09, 2004 10:42 AM
> To: alt-photo-process-l@sask.usask.ca
> Subject: Adjacency Effects Again
>
>
> In a recent thread the subject of adjacency effects was discussed. I
> have some further questions about that I wonder if any of you might
> like to address.
>
> The literature on this subject appears somewhat contradictory.
> Richard Henry notes that since the creation of adjacency effects is
> via lateral diffusion the type of agitation should in principle not
> matter, and he observes that he obtained adjacency effects with very
> vigorous and constant agitation. Yet he notes that research quoted by
> Todd reached different conclusions on the importance of agitation.
>
> Also, some sources suggest that only metol based developers give
> adjacency effects since phenidone is highly resistant to the
> restraining action of bromide. And on this list Ryuji mentioned that
> the development by products of certain reducers (he mentioned
> hydroquinone, catechol and pyrogallol as I recall) reduce or
> eliminate adjacency effects.
>
> In spite of any of the above I have been able to get very extreme
> adjacency effects with Pyrocat-HD and minimal agitation procedures,
> and I do not get them with constant agitation. And I believe Judy
> mentioned that she was able to get adjacency effects using
> hydroquinone.
>
> I would welcome further comments on these issue from Ryuji or any
> others on the list who may wish to comment. Also, if there is any
> recent literature relevant to the subject it would be nice to have
> the source.
>
> Sandy King
>
>
>
>
Received on Fri Apr 9 09:13:02 2004