Over-fixing film?
Michael Johnson
Here's one (and a half)...
I'm aware of the problems caused by incomplete fixing but can one
"over-fix" film? I ask because kodak fixer didn't seem to clear Tmax
3200 in 5 minutes in a hand-agitated tank. Five more minutes did the
trick however.
On a parallel note, is it possible to "over-wash" film? I use good ol'
chlorinated tap water of the appropriate temperature and I'm talking
about reasonable (not days long) washing times. I finish the wash with
three tank exchanges of DI water to avoid water spots.
Thanks in advance,
Michael Johnson
Los Alamos, NM
Kamil Horák
shadows (lightest part of the negative) could be theoretically "eaten" by
the fixer. Normally the fixing time should be twice the time necessary to
clear the film, extending beyond this time does not make any sense.
Same for washing, over one hour you increase the risk of damaging the
emulsion either by something (rust) from the water pipes or by softening it
too much.
Kamil, Prague, CZ
Michael Johnson píše ve zprávě <3C17B156...@lanl.gov>…
>I'm aware of the problems caused by incomplete fixing but can one
>"over-fix" film?
>On a parallel note, is it possible to "over-wash" film? ..
Michael Gudzinowicz
> I'm getting started doing my own B&W processing and have many questions.
> Here's one (and a half)...
>
> 3200 in 5 minutes in a hand-agitated tank. Five more minutes did the
> trick however.
half of that determined for older emulsions. You might want to read
the TMax publication F32 on the EKC website <http://www.kodak.com>.
It is downloadable as a pdf file (F32.pdf).
I'd suggest that you two bath fixing with hardener if you intend to keep
the negatives for your lifetime. It is explained in detail in a long
article I had posted on the archival processing of film and paper. Rather
than repost it, go to google.com to find it by searching this newgroup for
the two words: gudzinowicz jarinb
Also, fixing times will increase with fixer use. I'd suggest that you
cut off the film leader prior to loading the reel, and check its clearing
time in fixer while you develop the film. Fix for a minumum of twice that
time.
"Over-fixing" might lead to a slight loss of density, however, if one
is consistent, the effect is never seen since it is part of the process.
Usually, reduction requires undiluted rapid fixer which has been
deliberately acidified with citric acid, and long immersion times. The
method is useful to remove dichroic fog.
> On a parallel note, is it possible to "over-wash" film? I use good ol'
> chlorinated tap water of the appropriate temperature and I'm talking
> about reasonable (not days long) washing times. I finish the wash with
> three tank exchanges of DI water to avoid water spots.
completely in 20-30 min. The only real danger is excessive temperature
which can soften the emulsion.
Rather than using three changes of distilled water, soak the film in
the following solution for a couple of minutes:
1 gallon distilled or deionized water
100 ml 70% isopropanol (pure rugging alcohol without additives)
10 ml Kodak Photoflo
After soaking, hang the film to dry without wiping it. Water will run off
to the bottom of the film in a sheet, and it won't leave droplets or spots.
Richard Knoppow
It is possible to overfix film but it takes a very long time even in
rapid fixer. The effect is to slightly reduce the density since hypo
will dissolve some metallic silver even thought its not a very good
solvent for it.
The extent to which the image can be bleached depends on its grain.
Fine grain silver dissolves faster than coarser grains. Film emulsions
are quite coarse grained compared to printing paper. So, where a warm
toned paper might show the effects of overfixing in half an hour film
will take a lot longer.
Film is much harder to fix than paper emulsions because nearly all
film contains some silver iodide in its makup. Silver Iodide is used
in combination with silver bromide because it results in much geater
speed than bromide alone. However, its not as easily changed to a
soluble compound by the fixer and the iodide ions cause the fixer to
work more slowly. Ammonium thiosulfate fixer (rapid fixer) is less
sensitive to Iodide than sodium fixer so it is recommended for fixing
film.
Some modern films, particularly T-Max, Delta, and Acros have much
more silver iodide in them than other films so take longer to fix.
The rule of thumb is to fix for twice the clearing time but some of
these films may need three times the clearing time. Its reqally hard
to overfix them.
Over washing is possible. About 1961 T.H.James, of Kodak
Laboratories, made the interesting discovery that a small residue of
Hypo left in an emulsion acted to stabilize it against the effects of
oxidants in the atmosphere. This was such heresy that Kodak didn't
publish anything about it until Fuji published similar results about a
year later.
Up til that time it was thought that _any_ hypo left in an emulsion
would eventually cause the image to fade by converting it to sulfide.
In fact, if the sulfiding is confined to a molecular layer at the
surface of the silver crystals they are given a substantial amount of
protection against further sulfiding and to oxidation.
---
Richard Knoppow
Los Angeles, CA, USA.
dick...@ix.netcom.com
Richard Knoppow
An incomplete version of this post was sent accidently.
It is possible to overfix film but it takes a very long time even in
rapid fixer. The effect is to slightly reduce the density since hypo
will dissolve some metallic silver even thought its not a very good
solvent for it.
The extent to which the image can be bleached depends on its grain.
Fine grain silver dissolves faster than coarser grains. Film emulsions
are quite coarse grained compared to printing paper. So, where a warm
toned paper might show the effects of overfixing in half an hour film
will take a lot longer.
Film is much harder to fix than paper emulsions because nearly all
film contains some silver iodide in its makup. Silver Iodide is used
in combination with silver bromide because it results in much geater
speed than bromide alone. However, its not as easily changed to a
soluble compound by the fixer and the iodide ions cause the fixer to
work more slowly. Ammonium thiosulfate fixer (rapid fixer) is less
sensitive to Iodide than sodium fixer so it is recommended for fixing
film.
Some modern films, particularly T-Max, Delta, and Acros have much
more silver iodide in them than other films so take longer to fix.
The rule of thumb is to fix for twice the clearing time but some of
these films may need three times the clearing time. Its reqally hard
to overfix them.
Because of the restraining effect of the Iodide a two bath fixing
system is particularly effective for high Iodide films. The Iodide
mostly comes out in the first bath leaving the second one working at
full speed. Two bath fixing is good practice generally but is an
especially good idea for modern films.
Over washing is possible. About 1961 T.H.James, of Kodak
Laboratories, made the interesting discovery that a small residue of
Hypo left in an emulsion acted to stabilize it against the effects of
oxidants in the atmosphere. This was such heresy that Kodak didn't
publish anything about it until Fuji published similar results about a
year later.
Up til that time it was thought that _any_ hypo left in an emulsion
would eventually cause the image to fade by converting it to sulfide.
In fact, if the sulfiding is confined to a molecular layer at the
surface of the silver crystals they are given a substantial amount of
protection against further sulfiding and to oxidation from polutants
in the atmosphers.
For this reason washing of film should be limited to about 30
minutes at 68F.
If a wash aid is used the wash time needed is only about five
minutes.
Film, because of the relatively coarse grain of negative type films
is less vulnerable to oxidation than prints or to very fine grain
films like microfilm, but the effect is still there; avoiding very
long washes is favorable to long image life.
The same thing is true of paper emulsions except that fiber base is
much more retentive of hypo than the emulsion, so relatively long wash
times become necessary. Nonetheless, very extended wash times for
paper, especially where a sulfite wash aid has been used, have the
same result of making the image more vulnerable to oxidation. In a
research paper on the effects of toners on image life, three
researchers from Kodak Labs reported that the protection from a slight
hypo residue was effective _even when the emulsion was toned with
Selenium Toner_.
Malcolm Smith
not the silver halide component. My experience is that to remove the purple
is made more difficult when hardener is used in the fixer (which I don't
believe is necessary for most film fixing) - I give my Tmax films agitation
for the first minute (one inversion every five seconds) and then two
inversions every 30 seconds thereafter a total time in the fixer of 5 min
seems to work.
My recommendation is not to use hardener with Tmax (even if you squeegee
water off like I do). Richards words in his posts (as usual) can be relied
on for the fixing process itself.
regards
Malcolm Smith
--
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Michael Johnson <mjoh...@lanl.gov> wrote in message
news:3C17B156...@lanl.gov...
Richard Knoppow
>I suspect your clearing of the film is removing the Tmax purple tinge and
>not the silver halide component. My experience is that to remove the purple
>is made more difficult when hardener is used in the fixer (which I don't
>believe is necessary for most film fixing) - I give my Tmax films agitation
>for the first minute (one inversion every five seconds) and then two
>inversions every 30 seconds thereafter a total time in the fixer of 5 min
>seems to work.
>
>My recommendation is not to use hardener with Tmax (even if you squeegee
>water off like I do). Richards words in his posts (as usual) can be relied
>on for the fixing process itself.
>
>regards
> Malcolm Smith
>
Thanks for the kind words:-)
Hardener does no damage. T-Max films are much harder than most other
films; they seem to be hardened like color films, which are designed
to be processed at 100F. They probably don't need the extra hardening
but it does no harm.
When an alum hardener is used there is a tendency for it to mordant
the hypo molecules to the gelatin. The effect takes place only over
over a narrow range of pH. When the emulsion is treated with a bath
which brings the pH to a higher value the mordanting effect no longer
works and the washing out rate is the same as for unhardened emulsion.
An alkali bath of 1% to 2% Carbonate or Kodalk will stop the
mordanting but also removes the hardening. Sulfite wash aid, buffered
with bisulfite, as is done in Kodak Hypo Clearing Agent, adjusts the
pH to about neutral, at which point the mordanting is gone but the
hardening is preserved.
The original paper announcing sulfite wash aid has the interesting
information that, beside hypo, the solution also tends to make
insoluble silver complexes soluble. In other words, it makes it
possibel to wash out some of the otherwise insoluble complexes left by
incomplete fixing.
If the sensitizing dye in T-Max is indeed mordanted to these silver
complexes this would explain why wash aid gets rid of it.
In any case it seems to me good practice to use the wash aid even if
a two-bath fixing system is used. If the insoluble complexes are left
in the emulsion they soon change to a form which can no longer be made
soluble by subsequent fixing and, given time, will attack and damage
the emulsion.
The use of a wash aid, with either film or paper, considerably
extends the capacity of the fixing bath since a higher level of
otherwise insoluble silver complexes following fixing can be
tolerated.
While alum hardener does substantially slow down washing when no
post fixing treatment is used, it makes absolutely no difference in
the rate of washing when a sulfite wash aid is used.
The wash rate with the wash aid is considerably faster than is
gotten even with a non-hardening and alkaline fixing bath because of
the ion-exchange property of the sulfite. It actually displaces the
hypo from the emulsion.
Its interesting that the pH of the film is not the important factor
in its washing. The effect with the commonly used alum (Potassium
Aluminum Sulfate) hardener is a function of the hardener. When Chrome
Alum (Potassium Chromium Sulfate) is used the pH required to make it
work is considerably lower (more acid) than is requied by plain alum
but wash rate is the same as for unhardened emulsion.
Chrome alum is a very effective hardener but is not commonly used in
fixing baths because it has a short and somewhat unpredictable life
and will leave green stains on paper. Its used mainly in emulsion
manufacture and in tropical stop baths and fixing baths. Its also a
Valence VI chromium compound, meaning its a carcinogen.
BTW, I strongly recommend the final rinse suggested by Mike
Gudzinowicz in his post. Its a good preventive for water spots and
mineral deposits. I've been using it since he first suggested it and
get very clean negatives without squeegeeing.
>----------------------------------------------------
>Click here for Free Video!!
>http://www.gohip.com/freevideo/
>
>Michael Johnson <mjoh...@lanl.gov> wrote in message
>news:3C17B156...@lanl.gov...
>> I'm getting started doing my own B&W processing and have many questions.
>> Here's one (and a half)...
>>
>> I'm aware of the problems caused by incomplete fixing but can one
>> "over-fix" film? I ask because kodak fixer didn't seem to clear Tmax
>> 3200 in 5 minutes in a hand-agitated tank. Five more minutes did the
>> trick however.
>>
>> On a parallel note, is it possible to "over-wash" film? I use good ol'
>> chlorinated tap water of the appropriate temperature and I'm talking
>> about reasonable (not days long) washing times. I finish the wash with
>> three tank exchanges of DI water to avoid water spots.
>>
>> Thanks in advance,
>>
>> Michael Johnson
>> Los Alamos, NM
>>
>>
>>
>
>
---
Malcolm Smith
Greetings from ustralia - good to hear from you again! I will try wash aid
next tine I process Tmax (I usually use Agfa APX 100 for ISO 100 B&W). My
comments re hardener and the purple dye in Tmax films doen not come from any
extensive testing but seems from my experience to be a very significant
factor which can be applied with no effort.
Have a good Christmas and New Year - we will have a Christmas family
gathering with traditional hot turkey dinner even though it is the height of
the Australian Summer!
regards
Malcolm Smith
Richard Knoppow <dick...@ix.netcom.com> wrote in message
news:3c1855b1....@news.mindspring.com...