C41 Bleach: Pot.Ferricyanide Vs. Ammonium Ferric EDTA

[trendland]

Hallo everybody,

there are many advantages by working
with c41 chemicals when you not
use bleach and fixer as one solution.

Also named as "Bix" - just like, for example, the tetenal c41 home-kits contains.

This is offen discused here on APUG.
One can find so many tread as one
would like to read aboud this theme.

You are alternatively in the position
to choose seperativly chemicals from
Kodak also as from Fuji in commercial
packages.

They are often in 5 liter kanisters or
you can buy 2x5 liter to make 2x40l.
working solution and so on. ....
Dont forget the starters and sometimes the prebleach solution.

It has bekome really expansive over
the last years - unles you have to
develope 75 rolls negative film a week.

Alternativ formulas give you the chance
to make your own bleach solution.

Often with less costs.

Also here - you have advantages and
disadvantages.

Between several methods of c41 bleaching.

If you use a bleach on the base of
Ammonium Ferric EDTA you need
additional Ammonium Bromide.

(there are a couple of formulation here on APUG all of them works realy fine
I would say)

An interisting and economical fact on these is - that Ammonium Bromide is
also the replenisher herefore! !!!

What is with a bleach on the base of :

Pottassium Ferricianyde ?

Therefore you use additional Potassium
Bromide.

Has anybody an idea what chemical
can use for replunishment of a bleach
witch is based on Potassium Ferricianyde?

........I guess, but i am not shure :-(

with regards to you

 

[Rudeofus]

Developed color film contains sensitive dyes, which are carefully designed to create accurate colors. Just look at those molecules in patent literature, they are extremely complex. Predictably these dyes are sensitive to strong oxidizers, strong reducers, strong acids, strong caustics, you name it. They have, of course, be able to withstand the process conditions they have been designed for, and that's what they are tested and validated for.

Ammonium Ferric EDTA is a very mild oxidizer, in fact it is barely strong enough to bleach metallic silver, even with a bleach accelerator. C-41/E-6 designers picked it, because it gives them more leeway with their dye choice, and as a result better film products. Recent C-41 products have also been validated against Ammonium Ferric PDTA, a somewhat stronger oxidizer. Compared to Ammonium Ferric EDTA and Ammonium Ferric PDTA, Potassium Ferricyanide is a violent thug. Many people use it to bleach their color film, but don't come weeping to Kodak/Fuji if their color films can't handle it.

 

[trendland]

yes, I knew this.

PE mentioned it in some older Posts here on APUG -
I guess 2009.

That Ammonium Ferric PDTA is the latest
compound witch in use of Kodak.


with regards to you

 

[David Lyga]

Compared to Ammonium Ferric EDTA and Ammonium Ferric PDTA, Potassium Ferricyanide is a violent thug. Many people use it to bleach their color film, but don't come weeping to Kodak/Fuji if their color films can't handle it.

Since beginning the use of Potassium Ferricyanide with fixer for my C-41 and RA4 blixes over a dozen years ago, I have yet to initiate the 'weeping episode'. - David Lyga

 

[trendland]

........ yes of cause.But what rudeofus sayd was quite clear.

I would certailnly agree with him - in the
concerning of quality aspects with newest, modern emultions.

They changed also the chemistry at that
time.PE stated this in many other treads.

I would say on my personal demand as
a bleach component
Ammonium Ferric PDTA is the best
chemical for modern reformulated
T grained emulsions.

Because there is no other way to do the
job in highest standard.

And it is an originally compound of the comercial Kodak bleach you can by at different stores.

But that is not realy cheep. And it will
become more and more expansive in
the future.

But could it be a good way to pay 19,-$
for one new roll of slide film in the next
months (thinking of ektachrome at the end of the year) and don't spend enove
money for the corect E6 chemical?

I wouldn't do that so.

On the other hand Ammonium Ferric EDTA will do the job as a component
of a C41bleach twice as well - thats
my personal conclusion.

So at least i am absolutey in an agrement
with you that Potassium Ferricyanide
works well with normal films and this
since years.
May be i will use it for many older emulsions i still have.

What chemical do you use for replunishment of your bleach bath
David?


with regards to you

 

[Photo Engineer]

Potassium Ferricyanide can be used as follows:

Develop
Clearing Stop (Acetic Acid + Sulfite)
wash
Ferricyanide bleach
Clearing bath (Sulfite)
wash
Fix
wash
Stabilzer or Final Rinse

The clearing baths are needed to prevent stain.

Now, this works fine, but I cannot speak to image stability. Some stabilizing agents are oxidizable by Ferricyanide. The lower stability may not be noticed for months or even years.

PE

 

[trendland]

............absolutely correct PE as I may would say. There are some hugely important facts due to image stability.

Have read with highly interest some posts of you about the need for aditional formalin in stabilizer bath cause of kodak`s reformulated emoulsions ( E6 ). 2003 as I remember - cant find the original post yet.

And the subtitude of Kodak for formalin ( enviromental reasons aso. ) in their reformulated new Final Rise.

So when Kodak says there is very less silver ( or no silver at all ) in the film after all of the original baths - and they have found a new chemical to provide
that bugs are feeling hungry -it will be nice.

But beware of the same bugs without that new compound ore without rest silver or without formalin - one of theese 3 is still necessary.

Thinking of one old Slide Process, can not remember the name of it now, it was before Agfa´s AP-41 somerwere between 1967 - 1969.
I thing it could be " Revue Chrome " with their own process nothing to do with agfa - but they slides oldered in at least a few month,
slides of an age of 2 years were absolutely destroyed. And after max. 1 1/2 years they killed their Process and were from the market for ever with their
stuff.

That have had nothing do thing with bugs or with fungus ( not in that short time ) I thought their Process were absolut inefficent due to image stability.

So as it could be here !

Outside the original specifications may be allways an experiment. Slides will be looking fine by visual inspection every 2 years up to what year....?????

In 6 years, ... in 14 years .... in 17 years..... nobody knows.

Therefore, because of thinging about possible trouble in many days from now I personally wil be cautious with excellent, new film stocks.

My older C41, some E6 stuff wich were refrighed some years, do not care about potassium ferricyanide, may be they do not care on bugs
outside the refright too .-)


thanks for lots of very usefull information


with regards to you

 

[Rudeofus]

I think that PhotoEngineer did not refer to Formalin, which is apparently just one of the compounds used to keep the dyes stable over decades. If I interpret his post correctly, there are dye stabilizers built into the emulsion, and there is a chance, that they will be destroyed by Potassium Ferricyanide or equally powerful oxidizers.

 

[RPC]

If that is what he meant, then if one uses ferricyanide bleach, then perhaps one might benefit from using the old stabilizer instead of final rinse?

 

[trendland]

Yes - you are right Rudeofus here it has gone about the strong oxidative potential
of Potassium Ferricyanide due to more
inresistence ( sensitive ) dyes in modern emulsions and that they can interact
with strong oxidizers in a way they aren't
designet for.
You named them as "violent thug" .
In conclusion with image stability I am just remembering at the last post the need
of formalin in final rise (aditional) - as
PE. mentioned in some older Posts.

As I have understood that corectly you
need no additional amound of formalin
in the final bath (where asked here by one others) - no of cause not.

2-3% should be quite enough therefore
but it is needed when you use Kodaks
new E6 chemestry with older slide emulsions (before 2003 ?) because they
banned formalin.

And the fact is thats this makes nothing
to c41 but to E6 cause of less silver in the emulsion afterr final rise.

Indeed very interesting if you use original new E6 chemicals from Kodak
with ektachrome100sw for exampel.

You will not see any difference - of cause
not.But after years?

Back to Potassium Ferricyanide it might
be to strong as modern sensitive dyes and complex color layers are designed for.

They love Ammonium Ferric PDTA,
and were not as bussy with Ammonium
Ferric EDTA because PDTA is a little stronger - whether Potassium Ferrycianide is the beast in that club -
the violent thug as you named it.

with regards to you

 

[Photo Engineer]

AFAIK, all E6 products require formalin. NO C41 products require formalin.

It can be used, but the new final rinse baths contain a better biocide than formalin.

It should be noted that formalin can be oxidized by ferricyanide to produce formic acid which is not a stabilzing agent.

PE

 

[Rudeofus]

There are two reasons for having Formalin in a final rinse:

1. to scavenge uncoupled dye couplers before they react with stuff from the atmosphere, thereby improving image stability
2. to kill bacteria/fungus/germs/...

The first purpose is no longer necessary with modern C-41 film, but still required in current E-6 products. Note, that 7-bath E-6 kits put formalin into the prebleach bath, but AFAIK 3-bath E-6 kits have formalin in their final rinse - if they even come with one.

The second task is necessary for both C-41 and E-6. There are more effective compounds for this, and some C-41 kits use just a bactericide instead of formalin. However, few here will (and should) get their (gloved) hands on modern bactericides as raw compounds. While dilute solutions of these bactericides may be mostly harmless to us humans, in concentrated form some of these are quite unpleasant compounds, not to be handled outside of a professionally equipped lab. Therefore most home brew final rinses for C-41 and E-6 will use formalin. PhotoEngineer has given formulas in many threads including his sticky thread on final rinses.

@RPC: Formalin scavenges unused color coupler, but does little to stabilize final dye molecules. If I interpret PhotoEngineer correctly, there are dye stabilizers built into the emulsion to prevent dye decay. Remember how unstable old color film products were, how stable these are (claimed to be) today, this kind of improvement did not come by accident. If these built in dye stabilizers are made ineffective by strong oxidizer, you will not see negative effects right away, but they may/will bite you at some point in time.

 

[Photo Engineer]

Unused coupler could yellow and also react with dye to form colorless compounds as the processed film aged. This degraded the image severly. The problem has been eliminated in all C41 films.

Dye fading due to oxidation was slowed by use of Tocopherols (vitamin E derivatives) such as described by Lestina et. al. These can be oxidized right off in the process if Ferricyanide is used improperly or just by natural course of use due to reactivity.

I leave it to you all to judge whether it is the right thing to do. However, remember that Ferricyanide is a worse pollutant than Ferric EDTA or PDTA.

PE

 

[trendland]

Yes PE. that is quite clear to me from the beginning - Ferricyanides are more
poisonous.

The use of formalin is quite clear too.
I have mixed some facts due to memory gabs.

Yesterday I have read your whole sticky treat
a second time - originaly I have it in
mind from last year.

It is 1 % ( 10ml to 1l ) of formalin in final rise you recomanded.

But some aditional aspects to potassium
ferricyanide.

When dyes faded out with strong constance to all colors over years.

It could have lots of possible reasions.

- 1. physicaly
- 2. chemicaly
- 3. envirentmentaly
- 4. biologicaly

1,3,4 would most have an effect as an inclusion of all layers.

What are the most chemical problems with dyes - therefore the importance
of stabilizers ? The lost of color/contrast of different layers should
be constantly but this is not so - it is
an ideal.

The most dangerous effect of potassium ferricyianide is not that it may damage
image stabilizer agents and there may
be lots of different agents - it may not
destroy parts of sensitive dyes - because
it will do this - the question is only how
much.

Do you agree with me that the very
largest damage is the destruction of
the sensitive ballance of all layers to
several stabilizers,with lots of different
impacts, and with the ballance to each other (layer).


with regards to you

 

[Photo Engineer]

Formalin is 37% here in the US. I use 3 - 10 ml of that to 1 liter of water with Photo Flo 200 in it. Therefore the dilution is quite a bit lower than you describe.

Each dye can fade by a different mechanism. And air pollution, humidity, temperature and ambient light all contribute to this. I cannot be more specific because this question is so complex. For example, the vitamin E type stabilizer works best on magenta dyes, but forming a crystalline dye by manipulation of the structure of the solvent and coupler is best for yellows.

These are just a few generalizations. Thats it. I could write a book on this subject and still not be finished with the nuances.

PE

 

[trendland]

Yes you are right - I can image the complex implications in regard of the design of modern film emulisions.

I yust wanted to cover out - that here on the theme for hombrew bleach , thinking on advantages and disadvantages, it is a question of years.


If you have a lost of 40 % color saturation/color contrast evenly distributed throughoug each color this could be the case after 25 years with simple
storage conditions - you may not notice this.

Slides were not so much saturated / for c 41 its allmost an aspect in color management for the prints in the darkrom.


That means you can afford the fade out of dye layers in quantities of an max. 40%. If you have a fade out with is higher - lets say you have a color saturation/contrast

with a rest of 30% ( after 31 years under worse storage conditions ) c41 stuff may have a digital color resauration, slides will looking extremly bad.


This will show that true color ballance over so many years needs an absolut maximum of scientific research and applys lots of scientificaly provement.

You have been involved in this.


The problem is an realy problem if one color is faded out much more than the others and this in smal quantities even at the beginning ( after development ) .


Everybody can imagine what this means especially with E 6 material.


Then the process is insufficient. Thinking on the oposite side to those kind of insufficiency : K 14 - Kodachrome



Potassium Ferricyanides may cause this effect - slides becomes therrible colors but the process of this will beginn not directly after devellopment.

It has an affect witch can described as follow : After an undefined period of time ( lets say 19years of storage under good conditions ) one color is

in a fade out quantity with has suddenly a rate quite a bit more than the others.

Thats the end of those film after 12 more years of storage.


The reason herefore is definitifly to search in an absolute, an extreme fine ballance of modern sensitive dyes with stabalizer agents and coupplers.

If this ballance is not upset for many years - this is the design criteria - am I right ? And Ferricyanides have only a smal affect on this fine ballanced system

but thats enough to destroy it.


By the time achivement experts stated out that color film ( and prints ) are not archivable. BW films and prints are durable archivable.

Wy is this so ?? Because professional archivists are thinking in terms of less than 200 years or more than 300 years.

80 years as a maximum for slides are not on their schedule. In most cases ( after 80 years ) they are bw with absolut less contrast then.

Accept Kodachrome !


with regads to you

 

[trendland]

.......sorry I forgot one thing - Kodak !

They anounced that E6 ( after some smal modifications in the mid. 90th ) have now a durability with an absolut max. of 125 years ( under extremly restricted
storage conditions ) - wether they give Kodachrome 200 years ?

And they give E6 the chance to have a lost of 35% saturation in that time - also they do it to with K 14 to compare it.

Thats theoratically and may be correct - otherwise Kodak would not say so.

But it is not the pratice in storage



with regards

 

[Photo Engineer]

Unfortunately, dyes do not all fade at the same rate.

PE

 

[trendland]

Especially agfas RSX II - i have that very good in mind

with regards