Ilford Wash Procedue
Steven Woody
invised wahs procedure which use three tanks of fresh water with
agitation rather than using all the time running water.
i think i like the method because it save water and don't ask for any
washing gear. but it seems the method is designed for non-hardening
fixer. so i want to ask:
1, does the method still valid if what i used is a fixer such as
Kodak F-6a. should i modify the procedure?
2, if i switch to use non-harding fixer, such as Ilford's rapid
fixer, will it bring any harm on those legendary films such as kodak
Tri-X ?
another question is, if i also want to use washaid in the overall
process, how do i modify the Ilford's procedure?
thanks in advance.
-
woody
Geoffrey S. Mendelson
> by searching the net, i've got know that the Ilford introduced a
> invised wahs procedure which use three tanks of fresh water with
> agitation rather than using all the time running water.
>
> i think i like the method because it save water and don't ask for any
> washing gear. but it seems the method is designed for non-hardening
> fixer. so i want to ask:
Wash aids, as you called them were invented after someone found that
washing film in salt (ocean) water worked a lot better than washing
them in regular water. Probably someone on a ship. :-)
I've used various ones since the 1960's with all sorts of film and
fixers.
I think the bottle I currently have was made by Tetnal. Kodak makes (made?)
one called "Hypo Clearing Agent". There are lots of them around and they
all basicly work the same way.
Rinse the film for 1 minute, soak in chemical for a minute, was for 5
minutes. I think that was for "archival" processing, for "regular",
it was 30sec rinse, 30sec soak, 1 minute wash.
The new low water methods are not much different. Instead of constant flowing
water, they are fill and drain, fill and drain. This makes it more reliable
than guessuing the flow rate of the running water.
Geoff.
--
Geoffrey S. Mendelson, Jerusalem, Israel g...@mendelson.com N3OWJ/4X1GM
IL Voice: (07)-7424-1667 U.S. Voice: 1-215-821-1838
Visit my 'blog at http://geoffstechno.livejournal.com/
David Nebenzahl
> Steven Woody wrote:
>
>>by searching the net, i've got know that the Ilford introduced a
>>invised wahs procedure which use three tanks of fresh water with
>>agitation rather than using all the time running water.
>>
>>i think i like the method because it save water and don't ask for any
>>washing gear. but it seems the method is designed for non-hardening
>>fixer. so i want to ask:
>
> Wash aids, as you called them were invented after someone found that
> washing film in salt (ocean) water worked a lot better than washing
> them in regular water. Probably someone on a ship. :-)
Yes; U.S. Navy, WWII. (Right, Richard?)
> I think the bottle I currently have was made by Tetnal. Kodak makes (made?)
> one called "Hypo Clearing Agent". There are lots of them around and they
> all basicly work the same way.
The simplest, if you can get it, is plain old sodium sulfite. Cheap &
easy to use. That's what most HCA is, anyhow.
--
Any system of knowledge that is capable of listing films in order
of use of the word "fuck" is incapable of writing a good summary
and analysis of the Philippine-American War. And vice-versa.
This is an inviolable rule.
- Matthew White, referring to Wikipedia on his WikiWatch site
(http://users.erols.com/mwhite28/wikiwoo.htm)
Richard Knoppow
"Steven Woody" <narke...@gmail.com> wrote in message
news:1181990174.1...@i13g2000prf.googlegroups.com...
Both Kodak and Ilford have instructions for washing
using successive baths of water. This is quite useful when
there is no running water and is conservative of the water.
Kodak uses about 6 baths of constant time, Ilford uses fewer
baths with the time in each bath starting out short and
becomming longer. The total time for either is about the
same but the Ilford method probably uses less water while
the Kodak system is easier to keep track of. The overall
time is about the same as it would be for a running water
wash.
The use of a sulfite wash aid like Kodak Hypo Clearing
Agent reduces the wash time for film by about 6 times. The
normal wash time for untreated film in running water is
about 30 minutes. After a two minute treatment in KHCA the
required time is only 5 minutes.
Kodak HCA and the current Ilford product are probably
identical or nearly so. Kodak has published a technical
paper on KHCA and there is some additional information in
the patent. While the solution is mostly Sodium Sulfite
Kodak has added Sodium Bisulfite as a buffer and two
sequestering agents: EDTA Tetra-sodium salt, and Sodium
Citrate. The solution is buffered to neutral pH. At this
value the hardening produced by white alum hardening fixing
baths is not destroyed but the mordanting effect of the alum
for thiosulfate is. Also, at neutral pH the electric charges
in the gelatin are such as to repel the thiosulfate ions
rather than to attract them as it does when acid. The
Sulfite acts as an ion exchange agent displacing the
thiosulfate ions and fixer reaction products which may not
wash out without it. This compensates to some degree for
partially exhausted fixing baths. The purpose of the
sequestering agents is to prevent the deposition of Calcium
and Magnesium salts from hard water on the film and to
prevent sludging from carried over alum.
The research leading to KHCA was an extension of work
done to discover why sea water was more efficient than fresh
for washing photographic material. While this fact was known
before 1900 the reasons remained something of a mystery
until the middle 1950's. Sea water washing was extensively
used, especially by the Navy aboard ship, during WW-2. A
fresh water rinse is necessary after the use of sea water
because the halides remaining in the emulsion will quickly
destroy the image. However, little water is needed for this
rinse so the method is very conservative of fresh water. The
use of a sulfite wash aid like KHCA is even more effective
than sea water and much more effective than the old trick of
treating film or paper with a mild alkaline bath.
Check the Kodak and Ilford sites for specific
instructions about the sequential bath washing but for the
Kodak method the time is about 5 minutes in each bath with
constant agitation in each. If KHCA is used I suggest at
least two shorter baths to a total time of about 5 minutes.
This same system will work for paper. RC paper washes out
very quickly without a wash aid so probably two or three
short baths with a total time of around 5 minutes will do.
Fiber should be treated in KHCA and washed for the total
times recommended using about 5 minute baths.
The sucessive bath method is fully as effective as
running water washing.
--
---
Richard Knoppow
Los Angeles, CA, USA
dick...@ix.netcom.com
dan.c...@att.net
>
> i think i like the method because it save water and don't ask for any
> washing gear. but it seems the method is designed for non-hardening
> fixer. so i want to ask:
>
> process, how do i modify the Ilford's procedure?
>
>
I use the Ilford sequence in a relaxed manner. The 5-10-20 inversion
sequence is done a few inversions at each fill up and at least those
number of inversions are completed prior to the next fill-up. Some
still time is allowed while I clean-up around the darkroom. Photo
Flo rinses of film and eight blade film squeegee are last.
Films have been pre-hardened for many years. IMO, do without
hardener. A fresh fix of sodium thiosulfate alone will do the job.
Try a good half ounce, 16 grams, of the anhydrous in 500ml
of water. Allow 10 minutes with more of less continuous
agitation. Easy fresh fix each film or films. Dan
Richard Knoppow
<dan.c...@att.net> wrote in message
news:1182037762.1...@z28g2000prd.googlegroups.com...
shorter fixing times required by "rapid" fixers probably
don't give the hardener enough time to work anyway.
If a sulfite wash aid is used there is no difference
between wash time for hardening or non-hardening fixing
baths. Its not the "hardness" of the emulsion but the
mordanting effect of the common White Alum hardener which
causes the increase in washing time plus the acid condition
needed for the hardener to work. The pH adjustment made by a
Sulfite wash aid affects both of these factors as I
mentioned in my last post. Ideally, the pH of the emulsion
should be about neutral. At neutral pH the hardening is
preserved (sometimes it _is_ desirable) and the emulsion is
raised above its isoelectric point where the thiosulfate is
no longer attracted to the emulsion by charge.
A non-hardening or "plain" fixing bath should have some
Sodium sulfite in it to act as a preservative for the
thiosulfate and also to counteract staining from any carried
over developer. In an acid fixing bath the developer is
immediately inactivated but it will remain active for a time
even in a neutral fixer and especially in an alkaline fixing
bath. Film or paper to be fixed in a non-acid bath should be
very well rinsed after developing. Again, there is an
advantage to the use of an acid fixing bath because it
allows the use of an acid stop bath instead of a plain water
rinse. The acid stop bath immediately stops development
without any chance of staining from diluted developing
agents as is possible in a plain water stop bath.
For a plain fixing bath about 5 grams/liter of Sodium
Sulfite is enough. The much larger amount, typically 15
grams/liter, found in acid fixers is because the Sulfite
must also preserve the thiosulfate from being decomposed by
the acid. It is the reaction between the sulfite and acid
which results in the odor of Sulfur dioxide which is common
for fixers and which many people find very irritating.
Non-acid, non-hardening fixing baths are perfectly
satisfactory provided that an adequate rinse is given
between developer and fixer, an actual short wash rather
than just a few seconds in a tray of water.
Even though a neutral fixing bath will result in
significantly shorter wash times than an acid hardening
fixing bath the use of a wash aid will further shorten the
wash because of the specific ion exchange property of
Sulfite for thiosulfate and some fixer reaction products.
Steven Woody
> <dan.c.qu...@att.net> wrote in message
thanks for replies from all you folks! but i still get below
questions not so clear:
1, you folks tend to think hardening fixer is not neccessary for
films because most of modern films are already pre-hardened. is it
true for traditional Kodak 400TX roll films? and, is it true for RC
and FB papers?
2, i still got bottles of Kodak F-5 which is a kind of hardening
fixer, and i still want to use it. below are a fill-and-drain style
of prededure i designed after study your replies and Ilford's method,
would you give opinions about if it is okay?
step 1, fix using Kodak F-5
step 2, rinse using clear water, 30 secs.
step 3, washaid ( Ilford washaid or Kodak's Hypo-Clearing Agent ), 1
to 2 minutes
step 4, drain and fill tank with clean water, invert it 5 times
step 5, drain and fill tank with clearn water, invert it 10 times
step 6, drain and fill tank with clean water, invert it 20 times.
step 7, Kodak phot-flo, 30 secs.
some notes about above precedue,
a, step 4 to step 6 are directly copied from ILford's method which
assumes that fixer is non-hardening and no washaid was used.
b, the time for step 3 is directly copied from Kodak's publish for
some films including 400TX.
c, if i use non-hardening fixer, step 1 and step 3 can be skipped, am
i right?
3, Richard, after searched Kodak's site, i've not yet found publishes
about what you menthioned the wash method Kodak introduced which, you
said, is similar to Ilford's method. would you please give me an URL?
thanks.
5, about the one-shot plain fixer, would anyone please give me an
exact formular? i like to try it some times later.
Digitaltruth
> films because most of modern films are already pre-hardened. is it
> true for traditional Kodak 400TX roll films? and, is it true for RC
> and FB papers?
Unless a material or process specifically recommends use of a
hardener, you should avoid using one. Kodak Tri-X 400 does not require
a hardener.
Steven Woody
thanks a lot. i still looking for replies on the others questions.
Toni Nikkanen
> Unless a material or process specifically recommends use of a
> hardener, you should avoid using one. Kodak Tri-X 400 does not require
> a hardener.
What would be the negative effects of using a hardener for a film that
does not recommend the use of hardener? I'm asking because I mixed a
fixer with hardener for EFKE KB25 and I'd like to use the same fixer
for Tri-X 400 (135mm) that I'm going to develop next, but of course if
it's going to cause problems I'll have to make another fixer for
Tri-X.
John Boy
t-stick and stick it in the toilet. Flush six times with one minute
between flushes. Done.
I'll bet the archive fanatics are rolling over in their soup now.
dan.c...@att.net
>
> > <dan.c.qu...@att.net> wrote in message
>
>
> > > without
> > > hardener. A fresh fix of sodium thiosulfate alone will do
> > > the job.
> > > Try a good half ounce, 16 grams, of the anhydrous in 500ml
> > > of water. Allow 10 minutes with more of less continuous
> > > agitation. Easy fresh fix each film or films. Dan
>
> exact formular? i like to try it some times later.
>
>
One-shot plain fix. There are two versions of plain fixer, plain
and
very plain. Plain has a little sulfite added while very plain is
nothing but
sodium or ammonium thiosulfate.
The 16 gram or half ounce plus suggestion I made is a good starting
point. I intend to use that on a first roll of Acros 120 and expect
good results.
May take 10-12 minutes with off and on agitation. It will be used
fresh so
I don't bother with the sulfite. Also no stop of any sort; one-shot
fixer.
If you've a usual sort of rapid concentrate on hand try 20ml. All
solution
volumes are 500ml, one roll of film. After fixing it's down the drain.
One-shots can be prepared ahead in some quantity and amount each.
This evening I've four small prints to make. I'll prepare a print fix
ready for
a four way dilution. No used or ageing fix hanging around. Dan
Richard Knoppow
"Toni Nikkanen" <to...@morgoth.tuug.fi> wrote in message
news:rlpvedm...@morgoth.tuug.fi...
Hardening fixers became standard practice in the
early 1930s because emulsions were soft enough to have
problems with frilling and other damage during washing. Note
that the hardener works only when the film is wet.
Essentially, it reduces the amount of swelling. Methods of
improving the resistance of emulsions to mechanical damage
were made continuously from the 1930s (if not before) until
nearly the present. Up to about 1940 the standard processing
temperature was 65F, improvements in emulsion hardness
allowed that to be increased to the familiar 68 f about that
time. Some current B&W emulsions are hardened like color
film to withstand 100F processing. Among these films are the
Kodak T-Max series.
This hardening is partially due to the addition of
plastics to the emulsion. Even though research has been
carried out for a century to find a substitute for animal
gelatin for emulsions nothing has been found which works
nearly as well but other substances have been found which
can be added to it for improving, for instance, mechanical
properties.
Not all films and papers will withstand high
temperature processing or are resistant to damage when wet.
Hardeners in the fixing bath really do not do any
damage and can be used routinely. However, the fact that the
fixing bath must be acid for the hardener to work, and the
properties of the usual White Alum (to distinguish it from
Chrome Alum, a non-related chemical also used as a hardener)
result in the gelatin binding Thiosulfate ions and some
fixer reaction products.
Gelatin is amphoretic, that is, it is neither acid or
alkaline but has properties of both. Gelatin takes on the pH
of the last bath it was in. However, it has a sort of
preferred pH called the isoelectric point. This is the pH
where the gelatin molecules have no net elecrical charge.
For most photographic gelatin the isoelectric point is very
slightly on the acid side of neutral. At the isoelectic
point the swelling of the gelatin is minimum.
When an acid hardening fixing bath is used the residual
Alum binds thiosulfate and fixer reaction complexes in a
fasion known as mordanting. This is the way dyes are bound
in fabrics to keep them from bleading. The mordanting effect
takes place only in a window of pH on the acid side of
neutral. At neutral or alkaline pH the mordanting is no
longer effective. If the emulsion is made more than slightly
alkaline the hardening effect of the alum is lost. The
gelatin pH is also important in binding thiosulfate and
complexes due to electric charges in the atomic structure of
the gelatin. Everyone knows that opposite charges attract
and similar charges repel. The electric charge in gelatin is
related to its pH. As stated above at the isoelectric point
the charges are balanced so there is no net charge. On the
acid side the charges are so as to attract the thiosulfate
ions and some complexes. If the gelatin is made slightly
more alkaline than its isoelectric point the charges will be
such as to repel so washing out is accellerated. The charge
effect takes place even if a hardener is not used.
It has long been known that treating an emulsion in a
weak alkaline bath accellerates washing. It does so by
breaking the mordanting of alum hardener (when it is used)
and adjusting the pH of the gelatin to the alkaline side of
the isoelectric point. However, the gelatin needs only to be
made neutral to obtain both of these advantages and,
further, will have minimum swelling at that point.
The use of Sodium Sulfite and other Sulfites as wash
aids was discovered at Kodak Reserach Labs in the mid 1950's
as the result of research into sea-water washing. Sea water
will wash out Hypo in about half the time of fresh water but
itself must be washed out with fresh water. Sea water
accellerates washing more than a simple aklaline solution
such as a 2% solution of Sodium carbonate or Borax so they
decided something else beyond simple pH change was occoring.
This was discovered to be an ion exchange effect. Some ions
will actively displace others. Kodak discovered that
sulfites have a very strong ion exchange action for
thiosulfates and thiosulfate-silver complexes. The basic
wash aid was a 2% solution of Sodium sulfite. However, it
was also found that by neutralizing the solution the gelatin
was brought close to its point of minimum swelling.
According to Kodak this results in the shortest diffusion
path for the unwanted ions to reach the surface and be
washed away. Also at neutral pH the hardening effect of
white alum is preserved but its mordanting effect is broken.
So, there is good reason to buffer the solution.
Because the fixing properties of hypo are not affected
by pH it is possible to make a neutral or alkaline fixing
bath. Either results in faster washing than an acid fixing
bath whether hardening or not. However, a neutral or
alkaline fixer will still result in longer washing than if a
sulfite wash aid is used because of the ion exchange
property of the sulfite.
Since treatment in a sulfite wash aid will give the
shortest wash times regardless of the type of fixing bath
used it is, in general, a good practice to use it.
Acid fixing baths do have one virtue, they allow the
use of an acid stop bath which stops developing action
instantly and even if there is developer carried over to the
fixing bath it is inactive. While many have perfectly good
results using a neutral or alkaline fixing bath and a water
rinse stop this still has a slight risk of increased
development and staining. The last is probaby more a risk of
the water stop than of the fixing bath since any fixing bath
should contain some sulfite to preserve the hypo and that is
usually sufficient to prevent staining from developer
reaction products.
In short (I seem to be running very long today) there is
NO damage done by using a hardening fixing bath. The longer
wash times can be eliminated by the use of a sulfite wash
aid. There may also be no advantage to the use of a
hardening fixing bath especially for already well hardened
films and most modern papers.
If one looks at the recommendations for fixing time
given in old books one finds times like 15 or 20 minutes
recommended. These long times were partially due to the
assumption that partially exhausted fixer would be used but
also it was to give the hardener a long enough period to
work. Where relatively short fixing times are used a
hardening fixing bath probably does not do much hardening
anyway.
Of this slightly but it should be mentioned: The
capacity of a single fixing bath, whether Sodium or Ammonium
thiosulfate is quite limited. The use of two successive
baths is strongly recommended. It is important to the
permanence of a negative or print that _all_ the unused
halide in the emulsion be washed out. The purpose of the
fixing bath is to convert the insoluble halides to a soluble
form. Some of this comes out in the fixing bath and some in
washing. The conversion is a step-wise process the halides
becoming progressively more soluble. Incompletely converted
complexes will not wash out and remain in the emulsion where
they will eventually destroy the image. The ability of the
fixer to complete the conversion depends on the number of
free thiosulfate ions available. It takes about three
thiosulfate ions to convert one molecule of silver halide.
Once the complexing occurs the thiosulfate ions are no
longer available. By using two baths the bulk of the
conversion is done in the first bath leaving the second one
relatively free of dissolved silver and in condition to
complete the conversion of any halide left over from the
fist bath.
Since a sulfite wash aid will also eliminate the binding
of some insoluble complexes it gives further assurance of
complete fixing.
A further note: Compete fixing is more important to
image life than complete washing. It was discovered about
1960 (simutaneously at Kodak and Fuji) that a very small
residue of thiosufate remaining in the emulsion protected
the image from oxidation from air-borne peroxides. While
this is hard to quantify it is taken into account in the
wash times recommended by Kodak when its wash aid is used.
The heroic overnight soaks, etc, suggested in some older
books in not necessary and should be avoided. These long
washes actually reduce image life plus they can damage the
emulsion and, in the case of fiber paper, the support.
--
---
Richard Knoppow
Los Angeles, CA, USA
Nicholas O. Lindan
Most of my work is on DW fibre. I fix with rapid fix
(Arista/Ammonium Thiosulfate). Fix for 1 minute, holding
water bath for a few hours, second fix bath, Farmer's
(sometimes), Selenium, Rinse and hypo clear. I wash in a tray
with warm water, a water change every 1-10 minutes. I test
for washing with Kodak's HT-2 residual fixer test and
wash until there is _no_ stain on a test print.
With Kodak brand KHCA the prints wash out in 20 minutes or so,
~5-10 changes.
With Perma Wash it takes 1 hour+, ~10-20 changes, and
there is still a very faint stain.
I am rather surprised by this, but it has been the
case on two bottles of the stuff.
I notice most www'ers use Perma Wash only for film,
without much reason stated.
Anyone else with similar/different results?
--
Nicholas O. Lindan, Cleveland, Ohio
Darkroom Automation: F-Stop Timers, Enlarging Meters
http://www.darkroomautomation.com/index.htm
n o lindan at ix dot netcom dot com
Steven Woody
hi, dan
did you mean 16 gram sodium thiosulfate in 500ml for one roll of 120
film? how did you calculate that? i like to know any reasoning.
and, for one sheet of 8x10 paper, what's the amount for sodium
thiosulfate and water?
on the other hand, you said 10-12 minutes of fixing time, you know,
Kodak F-5 suggests 9 minutes. again, why you think the one shot fixer
need 10-12 minutes?
thanks.
-
woody
Steven Woody
> "Toni Nikkanen" <t...@morgoth.tuug.fi> wrote in message
Hi, Richard
thanks for your inputs, it's very in-depth coverage of the subject.
up to my understanding, you points are mainly:
1, hardening fixing makes no damage in any way;
2, hardening fixing makes no advantage on most modern films and
papers;
3, hardening fixing will take longer time to wash unless wash aid is
used;
4, acid is necessary for two reasons: (a) it is necessary when using
hardening fixer because the hardener has to be work in acid solution.
(b) it allow using of acid stop bath
5, wash aid is useful not only because it can shorten fixing time but
also i give further assurance of compete fixing.
to me, because i most likely process no more than 3 rolls one moth, so
i still look for one shot solution of fixing. because it is for one
shot usage, i think the formula should as simple as possible and the
amount of each ingredient should be as less as possible.
after study your inputs, i think i can decide,
1, use no hardening fixer because this will elminate at least one
ingredient --- alum.
2, use wash aid
3, because there will be no hardener in the formula, so i tend to
remove acid too. but, you said the acid solution allow using of acid
stop bath which is important in preventing incresed development from
happening, so i want to ask you, if i decide tol use acid stop bath,
what do i do to still use non-acid fixer? will it work if i insert 5
seconds of wather rinse after stop bath and before fix bath?
5, because i dont store the fixer, so i think i can further remove the
sodium sulfite. now only one thing left in the formula, that is sodium
thiosulfate only.
is the above okay? if so, how many sodium thiosulfate do i need for
fixing one roll of 120 film in 600 ml solution? and, how many the
same thing do i need for fixing a sheet of 8x10 paper in 900ml
solution?
thanks in advacne.
-
woody
Richard Knoppow
> n o lindan at ix dot netcom dot com
The MSDS for Permawash claims a trade secret for its principle
ingredient. It does contain Ammonium sulfite. By memory, this is one
of the salts mentioned in the Kodak patent. It is the anion rather
than the cation which is important and the patent lists several
sulfite salts.
I don't know why Permawash should be innefective but its
interesting to read your experience with it. The ingredients of KHCA
are pretty well known. The formula in the patent is not quite the same
as the MSDS mainly in that it does not have sodium citrate, a
sequestering agent. The patent formula lists only EDTA tetra-sodium
salt but the commercial product also has sodium citrate. The purpose
of the sequestering agents is to preclude the deposition of mineral
salts from hard water or a sludge of aluminum salt from alum hardener
on the emulsion. Otherwise KHCA is a neutral solution of Sodium
sulfite and Sodium bisulfite. The amount of the bisulfate might have
to be adjusted to account for the sequestering agents although they
are present in relatively small amounts.
I will post the patent number later for those interested. I am
away from home at the moment and do not have access to my references.
Nicholas O. Lindan
> The MSDS for Permawash claims a trade secret for its principle
> ingredient.
Better than filing for a patent. But the 'trade secret' doesn't
have to be anything but a secret. It doesn't have to work - could
be table salt or wetting agent.
> It does contain Ammonium sulfite. By memory, this is one
> of the salts mentioned in the Kodak patent.
Which tells you (or is supposed to tell you) just how to make
KHCA. The purpose of patents is to reveal what would otherwise
be trade secrets (a purpose I agree with), not 'protect the inventor'
(a purpose that makes no sense at all). "My invention is protected
by a patent!" - yeah, right...
> I don't know why Permawash should be innefective
It appears to contain 1/2 the amount of sulfites, with Ammonium
Sulfite instead of Sodium Metabisulfite.
Jean-David Beyer
> Otherwise KHCA is a neutral solution of Sodium
> sulfite and Sodium bisulfite. The amount of the _bisulfate_ might have
> to be adjusted to account for the sequestering agents although they
> are present in relatively small amounts.
Must be a typo. Sodium bisulfate would make the solution quite acidic, IIRC.
Is that not the active ingredient in toilet bowl cleaners?
--
.~. Jean-David Beyer Registered Linux User 85642.
/V\ PGP-Key: 9A2FC99A Registered Machine 241939.
/( )\ Shrewsbury, New Jersey http://counter.li.org
^^-^^ 10:25:01 up 6 days, 15:25, 3 users, load average: 4.58, 4.62, 4.36
Steven Woody
hei richard, please help :-)
jch
> interesting to read your experience with it. The ingredients of KHCA
> are pretty well known. The formula in the patent is not quite the same
> as the MSDS mainly in that it does not have sodium citrate, a
> sequestering agent. The patent formula lists only EDTA tetra-sodium
> salt but the commercial product also has sodium citrate. The purpose
> of the sequestering agents is to preclude the deposition of mineral
> salts from hard water or a sludge of aluminum salt from alum hardener
> on the emulsion. Otherwise KHCA is a neutral solution of Sodium
> sulfite and Sodium bisulfite. The amount of the bisulfate might have
> to be adjusted to account for the sequestering agents although they
> are present in relatively small amounts.
> I will post the patent number later for those interested. I am
> away from home at the moment and do not have access to my references.
For those of you who enjoy compounding your own solutions, i found this
substitute formula for Kodak's Hypo Clearing Agent in an old photo book:
SUBSTITUTE FORMULAS FOR KODAK'S HYPO CLEARING AGENT
The following formulas are used by the larger labs that mix
their own solutions:
WORKING SOLUTION - (not concentrate)
Water 1.0 liter
Sodium Sulfite 20.0 grams
Sodium Bisulfite 0.2 gram
The Sodium Bisulfite is in the formula only to lower the pH
to 7 - 7.5 to prevent softening the emulsion of film. If
papers are to be used, leave out the Bisulfite to deliberately
get more softening to improve the gloss. Also, to improve the
paper gloss, leave out all hardening agents in the fixing baths~
A concentrate of the above would be as follows:
Hot water 1.0 liter Dilute 1 part conc.
Sodium Sulfite 200.0 grams with 9 parts water.
Sodium Bisulfite 2.0 grams
DIRECTIONS FOR USE
After normal fixing, transfer prints or films to the clearing
agent solution with or without a water rinse. The water rinse
increases the capacity. 200 8x10 (or equivalent) papers or
150 to 200 8x10 (or equivalent) films per gallon of clearing
agent solution.
Water AT 65 to 70 F (18.5 to 21 C)
Papers Rinse Running
and After Hypo Clearing Agent Water
Films Fixer* (With Agitation) Wash
PAPERS
SW 1 min. 2 min. 10 min.
DW 1 min. 3 min. 20 min.
FILMS 30 sec. 1 to 2 mm. 5 min.
*Rinse after fixer may be eliminated. Capacity per gallon of
clearing agent solution will then be reduced to 80 8x10's or
equivalent for papers and 50 to 60 8x10's or equivalent for
films.
--
Regards / JCH
Nicholas O. Lindan
> I found this substitute formula for Kodak's Hypo Clearing Agent in an old
> photo book:
>
> WORKING SOLUTION - (not concentrate)
> Water 1.0 liter
> Sodium Sulfite 20.0 grams
> Sodium Bisulfite 0.2 gram
Interesting. For working solution, the formula
in Anchell works out to:
S. Sulfite 20 g / l
S. Bisulfite 5 g / l
and claims the Bisulfite should be eliminated when
glossing prints.
The formula I use to make concentrate, pinned to
the corkboard in the darkroom for the past ??? years:
S. Sulfite 15 g/l 2 tsp/l
S. Bisulfite 5 g/l 1 tsp/l
I mix it as a concentrate to dilute to 1:9
EDTA 1 Tbsp
S. Sulfite 300 g
S. Bisulfite 100 g
Water to 2 l
The EDTA amount is a WAG (Wild Arsed Guess) based loosely
on the observation that 1/2 tsp per liter keeps precipitate
from forming in D-72 stock solution.
Richard Knoppow
"Jean-David Beyer" <jeand...@verizon.net> wrote in message
news:8Ewdi.2726$Zh6.842@trnddc04...
My early morning typo, Sodium bisulFITE is the correct
substance. FWIW, it turns out that when Kodak specifies the
bisulfite they really mean an impure commercial version of
this substance which is at least half Sodium Metabisulfite
which will work in any of the formulas. Actual bisulfite is
evidently hard to package for some reason.
--
---
Richard Knoppow
Los Angeles, CA, USA
Richard Knoppow
"Richard Knoppow" <dick...@ix.netcom.com> wrote in message
news:1182174376.8...@n15g2000prd.googlegroups.com...
> On Jun 17, 10:00 pm, "Nicholas O. Lindan" <s...@sig.com>
> wrote:
>> FWIW -- my paper washing experience.
>>
>
BisulFITE, my typing error.
The patent for KHCA is USP 2,860,978 issued to Richard
Henn and John I. Crabtree and assigned to Eastman Kodak. The
formula given in it is:
Wash Aid Patent Formula (working solution)
Sodium Sulfite 20.0 grams
Sodium Bisulfite 5.0 grams
Sequesterine Na-4 0.5 grams
Water to 1.0 liter
Sequestrine is a brand name for EDTA Tetra-sodium salt.
The MSDS indicates the commercial product also contains
Sodium Citrate in an amount approximatelly equal to the EDTA
but MSDS quantities are in ranges of percents rather than
exact amounts so the amount of citrate might be anywhere
from 0.1% to 0.5% in solution. The commercial product is a
powder to make a concentrate. The concentrate is 5 times the
concentration of the working solution so its formula should
be:
Sodium Sulfite 100.0 grams
Sodium Bisulfite 20.0 grams
EDTA Na-4 2.5 grams
Sodium Citrate (probably) 2.5 grams
Water to make 1.0 liter
The instructions for KHCA suggest beginning with 750.0 ml of
water.
Sodium Metabisulfite will do instead of the Bisulfite.
According to Kodak and others commercial Bisulfite is mostly
Metabisulfite and this has been the case practically
forever.
It is probable that the sequestering agents can be left
out, it will depend on the water supply where you are. I
don't know how serious the problem wtih precipitation of
sulfite by the aluminum hardener is, perhaps not very. If
you try the formula without the sequestering agents and get
a deposit of mineral material on the film or paper then you
must add them.
--
---
Richard Knoppow
Los Angeles, CA, USA
dan.c...@att.net
>
> hi, dan
>
> Did you mean 16 gram sodium thiosulfate in 500ml for
> one roll of 120 film? how did you calculate that? I like to
> know any reasoning. And, for one sheet of 8x10 paper,
> what's the amount for sodium thiosulfate and water?
>
Sodium thiosulfate anhydrous 16 grams or sodium
thiosulfate pentahydrate 25 grams in 500ml H2O for one
roll of 120. That is not a calculated amount. That amount
was determinded by trial and error. I went through several
rolls of unexposed film arriving at that amount. Unexposed
film is worse case for fixer. Be sure and test a roll of your
film worst case using your procedures.
Currently I'm testing four DW FB papers; Slavich, Emaks,
Kentmere, and Arista. At present a 1% solution of sodium
thiosulfate anhydrous of 320 ml volume looks to do the job.
>
> on the other hand, you said 10-12 minutes of fixing time,
> you know, Kodak F-5 suggests 9 minutes. again, why you
> think the one shot fixer need 10-12 minutes?
>
The one-shot is very dilute. Perhaps 9 minutes will do;
depends some what upon the film. I may spend most of a
day exposing a roll of film. A few minutes more for processing
means nothing. Besides I don't wish to waste chemistry. Dan
>
> thanks. woody
>
Richard Knoppow
crystaline Sodium Thiosulfate or about 153 grams/liter of
anhydrous thiosulfate. I am quite skeptical about the
ability of a dilute fixer solution to provide adequate
fixing even if used only once.
I was going to refer you to an old post to this group by
Michael Gudzinowicz where he explains the fixing process
quite thoroughly, however, I find Google groups search to be
a bit of a pain these days to will copy and attach that post
to this one.
Mike's post begins here
-------------------------------------------------------------
This is part of one of my old replies on fixing, which
should cover your
concerns. BTW, use an acid stop bath, since any developer
carry-over
(still alkaline) to fixer will results in reduction of
soluble silver as
fixing begins, with possible staining and/or fogging as
likely results.
(The following are some of my notes on fixing film and
papers for
your personal use - not for distribution. Copyright (c)1995
by
Michael Gudzinowicz.)
The basis of fixation and accompanying problems aren't
treated in
depth in most texts. This oversight often leads to postponed
"accidents" whenever people are tempted by a sense of false
economy to save time or materials. An introduction to the
underlying chemistry should help to define a more critical
approach to film and paper preservation, which doesn't rely
on
rumor and the advertising literature. The following notes
were
taken from Grant Haist's "Modern Photographic Processing,
Vol.1"
(Wiley, 1979), "The Theory of the Photographic Process"
edited by
T. H. James (3rd & 4th ed., 1st & 2nd edited by C. E. K.
Mees;
Macmillan, 1966 (3rd)), "Ilford Monochrome Darkroom
Practice" by
Jack Coote, and the research and technical literature.
Stop Bath:
Compared to a water rinse, a dilute acidic stop bath will
stop
development very rapidly (15 sec) due to the pH change and
rapid
tunneling of protons compared, to a water bath where
developer
diffusion takes minutes (the basis of water bath
development).
The acid stop minimizes developer oxidation in fixers with
dissolved silver, which prevents soluble silver reduction
and the
formation of dichroic fog. Likewise, the pH change retards
aerial
oxidation of the developer and oxidation of fixer in the
emulsion
by radicals generated from the developer, which degrades
fixer
complexes to partially oxidized insoluble products which
stain
films and papers, and eventually cause fading and sulfiding.
Also, acid helps to maintain the pH of the fixer in a region
where it's stable, and where the hardeners are effective and
don't precipitate.
In addition, the use of a stop bath rather than water
reduces the
osmotic shock and resultant swelling of the emulsion which
is
seen when emulsions with high solute concentrations are
placed
into water, and thereby may reduce grain clumping.
Fixation:
The common notion is that the fixer removes undeveloped
silver
halide by a simple reaction involving the replacement of the
halide by thiosulfate to form a soluble silver complex, and
then
if the film or paper looks or tests "clear", the only
problem is
fixer removal. Unfortunately, this is not the case. When a
film
is "fixed", a number of complexes are formed between silver
and
thiosulfate, and all are in dynamic equilibrium. In
addition, the
accumulation of halide during fixation reduces fixer
capacity
with use when free silver and halide levels approach their
limits
of free, non-complexed solubility.
A simple table outlining the dissolution of silver in fixer,
and
equilibria with fixer is outlined below. The silver halide
may
dissociate to a very small degree in aqueous solutions, and
the
thiosulfate anion will form a 1:1 complex with the silver
cation
(Rxn 1) or the thiosulfate may react directly with the solid
silver halide crystal (Rxn 1). In either case, the first
complex
(I) is >very insoluble< and remains tightly adsorbed to the
surface of the solid silver halide.
A second thiosulfate anion may react with the first complex
(I),
to form a soluble product (II) with a silver to thiosulfate
ratio
of 1:2 (Rxn 2); and then if "free" thiosulfate
concentrations are
high, a third thiosulfate anion may react with the soluble
second
complex (II), creating a third complex (III) with one atom
of
silver and three molecules of thiosulfate which is quite
soluble
(Rxn 3).
Sequence of Complex Formation:
Note: Charge of ions in () brackets; # of molecules []# in
the
complex follows brackets; TS is thiosulfate (hypo) anion;
Ag,
silver; Br, bromide. <-> shows equilibrium reactions.
Rxn 1) Ag (+) + TS (-2) <-> AgTS (-) (first complex (I),
monoargentomonothiosulate; insoluble - remains adsorbed to
the
crystal as it forms)
Rxn 2) AgTS (-) + TS (-2) <-> Ag[TS]2 (-3) (aq) (second
complex
(II), monoargentodithiosulfate; soluble - removed from
emulsion
by diffusion)
Rxn 3) Ag[TS]2 (-3) (aq) + TS (-2) <-> Ag[TS]3 (-5) (aq)
(third
complex (III), monoargentotrithiosulfate; very soluble in
aqueous
solutions)
In solution, these reactions are reversible, so all
complexes are
present, and a small amount of Ag+ cation is not complexed
in
solution. The following equilibria occur:
Rxn 4) Ag (+) (aq) + TS (-2) <-> AgTS(-) (aq), where all
components are in solution (aq) and adsorption doesn't
occur.
Rxn 5) AgTS (-) (aq) + TS (-2) <-> Ag[TS]2 (-3) (aq) where
the
monoargentomonothiosulfate is in solution and not adsorbed.
Rxn 6) Ag[TS]2 (-3) (aq) + TS (-2) <-> Ag[TS]3 (-5) (aq)
where
both the monoargentodithiosulfate and
monoargentotrithiosulfate
complexes are in solution.
As more silver is put into solution with fixer use, more
complex
II & III are formed, and the level of the less soluble 1:1
complex (I) and free silver ion are also increased. After a
few
uses of fresh fixer, the less soluble complex (I) and silver
halide are left in the paper or film at low, but destructive
levels, although the film appears to clear. Also,
thiosulfate is
adsorbed to developed silver grains in papers (iodide tends
to
displace it from films). Residual complex I and residual
thiosulfate adsorbed to silver grains are converted to
trithionite and higher thionites in a few days, and degrade
and
react with silver giving stains (sulfiding) and fog. (Brown
silver sulfide is seen after bleaching the silver grains,
and is
proportional to the developed silver.)
With progressive use of the fixer, levels of bromide rise,
as
well as chloride from papers and iodide from films. Silver
halides have low solubility, and as the level of bromide or
iodide rises, it forms silver halide in solution and the
fixer
will no longer dissolve silver halide. A number of complexes
and
equilibria occur with each halide and mixtures. On a
relative
basis, silver chloride is more soluble than bromide and has
little effect on fixer capacity; silver bromide is less
soluble
and determines fixer activity to a significant degree,
unless
films with low levels of iodide are fixed, in which case
fixer
capacity is reduced significantly due to silver iodide
insolubility (a problem with T-Max films, treated later). In
instances where silver is removed to "regenerate" fixers,
iodide
accumulation may interfere. Also, in two-bath fixation which
follows, carry-over occurs, which requires periodic
replacement
of both baths.
The only way to ensure that little AgBr or the insoluble
first
complex is left in the paper, is to use fresh fixer with
little
accumulated silver and halide, and an excess of
non-complexed
thiosulfate to remove it. This approach to archival fixing
when
used with one bath is fairly wasteful, though effective.
Rather
than using one bath, the same results can be obtained with
two
baths, and the capacity of the fixer is far greater.
Essentially,
the first bath removes the bulk of the silver and halide,
and
leaves traces in the emulsion and paper. This amount when
carried
over to a second bath, is insignificant, so the second bath
always acts as "fresh" fixer with high non-complexed
thiosulfate
levels to react with the small amounts of silver halide and
less
soluble complexes to speed their complete removal.
More on Fixing - One and Two Bath Fixation:
Haist cites the following maximal permissible values for
one-bath
film and paper fixers for commercial and archival
processing:
One-bath fixation: Commercial Archival
Film:
Max. Ag conc.: 1.5g/l 0.2g/l
Max rolls/gal: 25 rolls/gal 2 rolls/gal
Non-image Ag in film: 0.01mg/in^2 0
Paper:
Max. Ag conc.: 0.3g/l 0.05g/l
Max. sheets/gal: 30 8x10 5 8x10
Non-image Ag in paper: 0.005mg/in^2 0
Essentially, as fixer total silver (free and complexes) and
halide concentrations rise, the fixer's ability to remove
all of
the silver from the paper diminishes markedly, as indicated
by
the very limited capacity of one-bath to remove silver to
archival levels.
The solution to the limited capacity is to use a fresh
second
fixer bath to maintain a very low total silver level, with a
water rinse between the first and second baths to minimize
fixer/silver carry-over.
Two bath fixation: Commercial Archival
Film:
Bath 1:
Max. Ag conc.: 6g/l 3.5g/l
Max. rolls/gal: 60-70 40
Bath 2:
Max. Ag conc.: 0 .5-1.5g/l 0.02g/l
after 60-70 after 40
Non-image Ag in film: 0.01mg/in^2 0
Paper:
Bath 1:Max. Ag conc.: 2g/l 0.8g/l
Max. sheets/gal: 200 8x10 70 8x10
Bath 2:
Max. Ag conc.: 0.3g/l 0.05g/l
after 200 after 70
Non-image Ag in paper: 0.005mg/in^2 0
The first fixer gets rid of most of the silver, and the
second
maintains a very low silver concentration and relatively
high
free thiosulfate concentration to remove the remainder of
the
insoluble complexes and non-image silver present in the
emulsion
after the first fixation.
The first bath is used for the maximum number of sheets or
rolls
indicated, and then discarded after silver recovery. The
second
bath is substituted for the first, and a fresh second bath
is
prepared. After 5 cycles (substitutions), or one week if
exposed
to air in tanks, both baths are replaced. Compare the
capacity
for commercial or archival standards using two baths to that
for
one... it is far more economical than using one bath, but
also
avoids the temptation to over-use fixer, resulting in under-
fixation and difficult removal of insoluble complexes.
Films:
With films, the fixation time in the first fixer should be
at
least twice the clearing time... likewise for the second
bath.
The clearing time should be checked often if that approach
is
used, however, Kodak recommends 5-10 minute fixation with
non-
rapid fixers and most films. Since there is no danger in
longer
fixing times, incorporating a five minute fix in each bath
into a
"normal" development procedure may avoid problems and
provide
some security. Agitation should be constant to remove fixer
from
the surface of the film to facilitate diffusion, however,
increased agitation never can replace adequate fixing time
or
counteract the cumulative effects of re-using fixer. With
rapid
fixers, there is little "danger" of bleaching film with 5-10
minute fixation... also, if standard procedures are used,
any
minimal bleaching would never be noticed, since it would be
incorporated into tests for contrast and development time.
With
T-Max films, Kodak recommends longer times. For instance,
they
suggest that it is "safe" to check clearing at five minutes
with
standard fixers or three minutes with rapid fixers... and
total
fixing time should be twice the clearing time. (Kodak's
"advice"
on T-Max varies from simplistic on 35 mm film boxes, to
warnings
in detailed technical literature, not only on times, but
also on
fixer replenishment rates for processors.)
T-Max Films:
With some films, such as Kodak's T-Max series, fixer
capacity is
reduced to one-half of what one normally expect, and fixing
times
are extended to twice the usual time, since silver iodide is
resistant to fixation. In Kodak publication F-32 on T-Max
films,
Kodak indicates that a magenta stain may be left in the
emulsion
with inadequate fixing, and recommends further fixing with
fresh
fixer to remedy the problem. (The magenta sensitizing dye is
adsorbed to the silver halide (EKC statement - not
speculation);
when the halide is fully dissolved, the dye is removed.) In
some
instances, the dye can be removed by treatment with
hypo-clear,
which may contain sulfite or high salt concentrations which
can
act as weak fixers in addition to displacing hypo, or with
prolonged water washes. The "stain" problem isn't whether it
will
interfere with variable contrast paper filtration or not,
but its
indication that the film isn't fixed properly.
Papers:
For paper fixation, do not use fixer which has been used for
film. It is difficult to track capacity accurately (see
table
above... silver capacity differs for film and paper), fixer
dilution may vary between paper and film fixers, and the
"sudden"
accumulation of iodide after developing films may greatly
prolong
paper fixation or may leave insoluble silver iodide behind
unless
one tests clearing times at every session.
The clearing time for papers may be determined
experimentally or
by manufacturer recommendation (for Ilford, see below).
Fixing
times for most fiber papers is on the order of five minutes
for
each bath, with an intervening water rinse and storage in
water.
To save time, prints can be fixed in the first bath, rinsed
and
held in water, then fixed in the second bath at the end of a
session. As mentioned, long contact with fixer can cause
problems
if fixer enters the paper fibers (not between them). Papers
and
fixers vary, and it is best to use at least the minimum time
recommended by the paper manufacturer. Kodak recommends 10
min
for fiber base and 2 min for RC in one bath, or half that
time
for each of two baths. The RC time is optimistic, though
five
minutes per bath is reasonable for fiber papers. Prolonged
contact with rapid fixers will slowly bleach an image or
cause
uneven bleaching if prints remain in rapid fix without
agitation
for prolonged times (1/2 hr+).
In any case, paper and film should be promptly removed from
the
second fixer, rinsed, and placed in a water bath until
treated
with a hypo clearing solution to displace free thiosulfate.
Rapid Fixer:
Rapid fix has the advantage of a shorter contact time, and
that
may minimize the penetration or degradation of fixer in the
paper's fibers. Also, the useful capacity of rapid fixers is
fairly high... 10-15 g/l silver vs. 6g/l for films or 2 g/l
for
papers using regular fixers (James; Haist table above for
bath 1
of a two bath sequence). However, there is little data to
extrapolate those numbers into increased capacity _without
risk_
of problems. In that regard, Kodak's recommendation for
capacity
of rapid fix and other fixers is nearly the same (100-120
sheets
or rolls), which is optimistic for one bath commercial
processing.
Hardeners:
For film, a hardening fixer is often preferred to minimize
any
emulsion damage in handling. The only advantage of rapid fix
with
film is decreased processing time and perhaps, decreased
rinse
time. Non-hardening fixers are also preferred for
development of
the stain with pyro developers.
For paper, rapid fix without hardener is often preferred,
and
gives better results with toning. Paper curl seems to be
minimized and there is less danger of "breaking" the
emulsion
when prints are flattened or mounted. Also, the avoidance of
alum
may reduce silver complexes bound in the emulsion. (To
remove
hardener for toning: household ammonia diluted 1:10 (0.3%)
for 2
min with 45 min wash; or 5 min in 2% solution of Kodalk or
sodium
carbonate, then wash).
------------------------------------------------------------------------
Mike's post ends here
--
---
Richard Knoppow
Los Angeles, CA, USA
Nicholas O. Lindan
to happen.
Steven Woody
> RE: On Jun 17, 11:59 pm, Steven Woody wrote:
>
>
>
> > hi, dan
>
> > Did you mean 16 gram sodium thiosulfate in 500ml for
> > one roll of 120 film? how did you calculate that? I like to
> > know any reasoning. And, for one sheet of 8x10 paper,
> > what's the amount for sodium thiosulfate and water?
>
> Sodium thiosulfate anhydrous 16 grams or sodium
> thiosulfate pentahydrate 25 grams in 500ml H2O for one
> roll of 120. That is not a calculated amount. That amount
> was determinded by trial and error. I went through several
> rolls of unexposed film arriving at that amount. Unexposed
> film is worse case for fixer. Be sure and test a roll of your
> film worst case using your procedures.
>
> Currently I'm testing four DW FB papers; Slavich, Emaks,
> Kentmere, and Arista. At present a 1% solution of sodium
> thiosulfate anhydrous of 320 ml volume looks to do the job.
what size of paper and how many sheets of these papers will a 320ml 1%
hypo solution do?
dan.c...@att.net
>
> what size of paper and how many sheets of these
> papers will a 320ml 1% hypo solution do?
>
That 3.2 grams of sodium thiosulfate anhydrous
will fix one 8x10. I'm ready to start a new series of
tests on the four papers I mentioned. I messed up on
a first series of test by introducing more than one
variable through the series of tests.
I've had more than one indication that carbonating the
fix noticeably speeds fixation and washing. I'll post back
in a few days with some results and additional confirmation
of what already has been claimed. Dan
at @the-wire.dotcom Lloyd Erlick
I've been operating my darkroom without acid
for years now, and I find Richard's comments
(below) absolutely accurate. In fact, his
first paragraph is essential.
I have to add something important, though --
the incredible ease and simplicity of it all.
Plain fixer is easy and quick to make up,
rinsing in tap water is a lot easier than
preparing acid stop, never mind smelling it.
Shorter wash time requirements from non-acid
fix, coupled with sulfite washaid, can very
easily result in rigourously correct,
'archival' prints. It's just easier and less
effort without acid.
My hatred of sulfur dioxide and hydrogen
sulfide made my decision!
regards,
--le
________________________________
Lloyd Erlick Portraits, Toronto.
website: www.heylloyd.com
telephone: 416-686-0326
email: port...@heylloyd.com
________________________________
--
On Sun, 17 Jun 2007 00:59:16 GMT, "Richard
Knoppow" <dick...@ix.netcom.com> wrote:
...
Richard Knoppow
"Lloyd Erlick" <Lloyd at @the-wire. dot com> wrote in
message news:3f8i73h9skafgfeno...@4ax.com...
The evolved gas is important. If you are sensitive to
Sulfur dioxide that can be enough to justify using an all
neutral process. The problem is that acid fixing baths
constantly emmit a small amount of Sulfur dioxide. Some
people are very sensitive to this gas which can set off
Asthmatic attacks and cause a choking sensation even in
those without asthma. Hydrogen sulfide is the gas with the
rotten-egg odor. It can result from fixing baths which are
nearing exhaustion but is not usual. It is more often
encountered when using certain kinds of sulfiding toners.
Any solution which emmits Hydrogen sulfide should be used in
a very well ventillated place, even outdoors and should be
kept away from unprocessed sensitive materials because the
gas is a prolific fogging agent.
A non-hardening fixing bath can still be acid but can be
less so than a hardening bath. The acid condition of the
hardening bath must be right for the hardener to work.
Without the hardener the fixer can be just acid enough to
inactivate carried over developer. Low acid fixer is much
less likely to produce irritating gasses.
at @the-wire.dotcom Lloyd Erlick
O. Lindan" <s...@sig.com> wrote:
>> I don't know why Permawash should be innefective
>
>It appears to contain 1/2 the amount of sulfites,
June 24, 2007, from Lloyd Erlick,
Maybe PW mixed at twice the recommended
concentration??
I've always just used a two percent solution
of sodium sulfite.
regards,
--le
________________________________
Lloyd Erlick Portraits, Toronto.
website: www.heylloyd.com
telephone: 416-686-0326
email: port...@heylloyd.com
________________________________
--
dan.c...@att.net
>
> I've always just used a two percent solution
> of sodium sulfite.
>
And I've been plugging Agfa's recommended
sodium carbonate. What happened? Dan
Richard Knoppow
<dan.c...@att.net> wrote in message
news:1182731913.0...@e9g2000prf.googlegroups.com...
anyway. The Agfa recommendation is based on work done in its
labs in the 1930's. Its well known that treating film in a
mild alkaline bath will increase washing rate especially
when its been fixed in an acid fixing bath. As I stated in a
previous reply the pH change affects the electric charges in
the gelatin so that they do not attract the Thiosulfate ions
but rather repel them. It also breaks the bond caused by
Aluminum sulfate hardener, however, it also destroys the
hardening effect. A plain alkaline bath, however, does not
have the ion-exchange properties of Sodium Sulfite. It is
this ion exchange effect which causes Sulfite to have such a
strong accelerating effect on washing. Of course, sulfite is
also mildly alkaline. The buffering to neutral pH in Kodak
Hypo Clearing Agent is about optimum for washing because it
eliminates the bonding caused by aluminum hardener without
destroying the hardening action.
While Agfa recommends 2% Carbonate nearly any mild
alkali, such as 2% Borax, will do if one wants only the pH
adjustment. However none will be as effective as the Sulfite
bath.
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Richard Knoppow
Los Angeles, CA, USA