----- 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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