[pure-silver] Re: holes in emulsion and temperature
- From: "BOB KISS" <bobkiss@xxxxxxxxxxxxx>
- To: <pure-silver@xxxxxxxxxxxxx>
- Date: Thu, 6 Dec 2007 15:59:39 -0400
DEAR RICHARD,
Two questions:
1) I had also read that modern films don't reticulate easily but it
was suggested that sudden changes in temperature from solution to solution
might cause "grain clumping" yielding a coarser grain pattern. Is this
true?
2) I live in the tropics here in Barbados. Those of us who use
darkrooms have the expense of air-conditioning because a closed room here
can get VERY hot. I have always taught my students to keep the temperatures
of all of the processing chems near the same temp. I also suggested that
processing at higher temperatures required some extra care. We bought a 20
pack of T-max 120 film and we shared it. We all used the same chemistry
("Rodinal Special" aka Studional) indicator stop bath, Kodak fix, hypo
clear, wash and Photoflo. One student worked at home (using the same chems)
and refused to cool his chemistry below 85 F but adjusted dev times
accordingly. He is the only one who got pinholes in his negs. When I
convinced him to cool his processing chems to 68 F, he didn't get any more
pinholes. Is there something in Rodinal Special/Studional that might cause
this?
CHEERS!
BOB
-----Original Message-----
From: pure-silver-bounce@xxxxxxxxxxxxx
[mailto:pure-silver-bounce@xxxxxxxxxxxxx] On Behalf Of Richard Knoppow
Sent: Wednesday, December 05, 2007 9:31 PM
To: pure-silver@xxxxxxxxxxxxx
Subject: [pure-silver] Re: holes in emulsion and temperature
----- Original Message -----
From: "Nicholas O. Lindan" <nolindan@xxxxxxxxxxxxx>
To: <pure-silver@xxxxxxxxxxxxx>
Sent: Wednesday, December 05, 2007 5:09 PM
Subject: [pure-silver] Re: holes in emulsion and temperature
> "Shannon Stoney" <shannonstoney@xxxxxxxxxxxxxxx>
>> holes in the emulsion of my recent negatives (120 roll
>> film)
>
> The usual suspects are:
>
> o An active developer - HC110b, say - followed by a too
> strong (made per Kodak's directions) stop-bath. Most
> people use a dilute stop bath or a plain water rinse.
> o Film made in Eastern/Comcon/Evil Empire
> Europe/Russia/China.
> These are/were given to pinholing. If you are using
> recent Arista film it is from former Eastern Europe.
>
> I had a brick (er bag) of old (~10 yr.) Arista branded
> Ilford FP4 that pinholed. The film was used in a Holga or
> Diana so
> the defects just added to the general je ne sais quoi; and
> it was well past any 'return before' date.
>
> I have had the odd pinhole with just about any film and
> process,
> but always with 120 (IIRC).
>
> re. Stopbath:
>
> You have to keep active developer from showing up in the
> fix as
> it can stain and shorten fixer life. A water rinse will
> wash away most of the developer still in a film emulsion.
>
> With fibre base paper you need either a stop bath or a
> _really_ good rinse.
>
> ==
> Nicholas O. Lindan
> Cleveland Engineering Design, LLC
> Cleveland, Ohio 44121
In the past pin-holes were blames on the generation of
carbon dioxide gas in the stop bath. This takes place when
the developer contains an alkali that causes effervescence.
About the only common alkali that does that is sodium or
potassium carbonate. HC-110 contains Diethanolamine-sulfur
dioxide complex which AFAIK does not cause gas to be formed.
Kodak's formula for stop bath is the same as given by
most other manufacturers, i.e. about 2%, usually stated as
one to one and a half ounces of 28% acetic acid per quart,
or about 50ml per liter of water. This should not cause
problems.
Pin holes in modern film is generally a result of
coating problems in manufacture. Ilford had a problem with
this some ten years ago and even Kodak has had occasional
problems. I have no idea what level of technology or quality
control applies to the former east block manufacturers but I
am suspicious that its far behind the state that Kodak,
Ilford, and Agfa got us used to.
Pin holes can also sometimes be the result of particles
of grit deposited on the film during processing as some
point where the emulsion is fairly soft but again I think
this was mostly a problem in the past. Nonetheless, its
worth filtering all solutions before use to see if that
helps.
Using a hardening fixing bath may help.
Real pinholes are actual disruptions in the emulsion.
They are visible on the surface using rather high
magnification. they can be mimicked by small clear spots
caused by dust on the negative when exposed or by small dark
spots usually the result of undissolved chemistry in the
developer. Not a chance of this with HC-110.
---
Richard Knoppow
Los Angeles, CA, USA
dickburk@xxxxxxxxxxxxx
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