CuSO4 Bleach vs Flexicolor Bleach Test #1

[Athiril]

I decided to try it.

Short of it: Film I used was so crappy, fogged and dense, it wasn't a great test, but it demonstrates Copper Sulphate Bleach works 'just fine'.

CuSO4 Bleach Recipe: 100g/L CuSO4, 100g/L Table Salt (sea salt, anti-caking agent, I had no straight NaCl, didn't seem to matter as far as I can tell). Also I didn't filter or decant it, I forgot, didn't seem to matter either.

Film: Unknown/unbranded 12-exp 400 ISO old and expired (50 cents a roll!) and fogged.

Exposure: EI 50.

Process:: Flexicolor C-41 (2min 45sec, was intending a "N-2" development), thorough rinse, weak sulphite bath/clear (had no metabisulphite left), thorough rinse, bleach (one frame was in flexicolor bleach, the other CuSO4 bleach), thorough rinse, weak sulphite bath/clear, thorough rinse, fix, thorough rinse, stabiliser.

Bleach time was 17 min as I walked away and forgot about it.

Results upon inspection after bleaching: This stage demonstrated CuSO4 bleach works, back of the film turned green/blue just like the flexicolor frame, and allowed me to see the image on the back of the frame, just like the flexicolor frame.

Results after fix and stabiliser: Dense, can't see any retained silver, bleaching looks complete.

Results after scanning: Dense, both reach same basically same max density, retained silver negative would increase this density well beyond the end of my scanner. Colour seems fine and correctable, though both hard to correct due to density, it's beyond the normal "maximum" density/level setting and would be clipped out on auto.

Red, Green and Blue densities all seem to have the same general separation as flexicolor bleached negatives. Need to test with fresh film and normal process to see where the mid tone levels for each red, green and blue densities lay in relation to one anotehr compared to a flexicolor bleached negative.

CuSO4 bleached negative exhibits broader density range for individual Red, Green and Blue densities, but is a completely different image (not the best test I know, but this is Test #1).

Image grain is increased for this film but not significantly over normal (believe it not - its rather quite crap), but I am putting that down to the high density, probably scanner noise because of that density too (it's a negative, and it's a V500, meaning crap sensor (and crap lens) and high density = right in the shadows on the sensor with the worst part of the SNR).

Film Density: Both are about the same, and are two comletely different images. The maximum density on my V500 is quote at 3.4, so assumedly it'd be near that figure, but I know thats crap, it's under 3, I 'm sure it's around 2.8, maybe even 2.6.

Conclusions: CuSO4 bleach works "just fine" and is worth more investigation on a more thorough test, and I can't comment on colour balance until I do so.

Another test should be done on fresh film, normal exposure, normal development, same images/scene/subject, and add in my poor-man's colour checker with same exposure for a comparison of flexicolor bleach vs CuSO4 bleach vs bleach bypass.

Image:

CuSO4 Bleach vs Flexicolor Bleach Test #1 by athiril, on Flickr

 

[Athiril]

Just an update, someone said it was not a rehalogenating bleach, so I did another little test.


I took a sheet of 4x5" Fomapan 100, cut a square off.

Put it in a beaker in the light so its well fogged (the sheet is sitting my room in the light also), developed in some Rodinal until completely black.

Rinsed a few times, sat in a beaker with water for a few minutes and rinsed again.

Put it in the CuSO4 + NaCl bleach at the same strength used for the colour film, it rehalogenated the fomapan 100 square in well under a minute at 20-24c.

Rinsing well as above, I put it back in the Rodinal and dveloped it again, re-develops just fine.

The film wasn't any thinner upon inspect with a backlight after bleaching compared to before developing.

It is a rehalogenating bleach as assumed.

 

[brucemuir]

interesting
what form of copper sulfate did you use for that formula/amount?

I'd like to see some near fresh film to see how the color comes out...

 

[Photo Engineer]

Cupric Sulfate will bleach silver images but will also leave Cupric and Cuprous residue behind in the film giving it an orange blue Dmin. I wish I had my data, but Cupric bleaches and Blixes were among the solutions that I investigated in the 60s and we rejected due to problems. There are lots of Copper based bleaches and blixes in the patent literature.

Among other problems, you cannot go into the bleach or blix from the developer due to formation of Cupric and Cuprous Hydroxides which remain in the coating. Addition of EDTA helps, but slows bleach time.

This is a rehal bleach, but due to the solubility of AgCl, the end result will be loss of some of the image. Also, since the bleaching action forms soluble Ag2SO4, you lose additional original Silver image.

PE

 

[Athiril]

Pentahydrate as its the most common (blue powder).

I have no fresh film in 35mm, though I have some Kodak Gold 100 from 2000-2004 in the fridge which is probably be fine, heaps of fresh 120... but I never like sacrificing it for tests. Though itd be good to shoot a scene twice, one for flexicolor bleach the other for copper sulphate and take one half of each in PS and merge to one layer then colour correct and see diferences.


Photo Engineer: I will have to develop and fix some b&w of a pictorial scene, scan, and then rehal develop it with a copper sulphate bleach and compare histograms to give an indication of loss, I couldn't notice any loss on the Fomapan by eye, but obviously its not thorough.

As above I'll have to do a color comparison.


So, the clearing bath after should be metabislulphite, not sulphite?

 

[mts]

In my tests of Cu bleach (On Vericolor II from the 1980s and repeated in the last year or so using Portra 160NC and Fuji 160S) I did not find any Dmin problem, although there is surely Cu left in the emulsion that could adversely affect long-term dye stability. It's not at all surprising that Kodak looked for and found better bleaches for production chemistry. I NEVER go from developer to bleach. I always use a 2% acetic acid/2 bisulfite stop followed with a good wash before bleaching. No matter what the experts say I have long found safe better than sorry with regard to stops and washes before bleaches.

My source for copper sulfate pentahydrate has been the hardware store where it is sold for removing tree roots from sewer lines. What is for certain, is that there is no more economical bleach possible! One can only wish that CD-3,4 could be had at similar price.

 

[Athiril]

Shouldnt acidic conditions (or perhaps a weak HCl dilution) remove Cu?

 

[Photo Engineer]

Cupric Sulfate bleaching is like using Dichromate - Sulfuric acid bleaching. The bleach forms Silver Sulfate which dissolves in water and therefore there is image loss. With halide present, this is repressed, but not totally stopped depending on pH and what halide is used.

PE

 

[brucemuir]

What is for certain, is that there is no more economical bleach possible! One can only wish that CD-3,4 could be had at similar price.

This is my interest in finding/exploring alternatives.

It's next to impossible to get C41 bleach and I do have a supply but it may last me another year hopefully.

 

[Athiril]

This is my interest in finding/exploring alternatives.

It's next to impossible to get C41 bleach and I do have a supply but it may last me another year hopefully.

Well its quite readily available here... at least from one single place in Australia.. should be easy to get in the U.S.

If it is a problem, have a chat with a developing place and ask if you can split their chemical order, one shop here was willing to do that with me at one point. Though I ended up not needing to.

Potassium Ferricyanide is only available from that one same place here afaik... and the price recently jumped up $20/kg to nearly $50/kg.

Hydroquinone went up from like $12/500gm to $10/100gm too! They did have big discrepancies in price/gm between small amounts and larger amounts.. but now they removed the larger amounts of some of the cheaper chemicals, really quite annoying.

Cupric Sulfate bleaching is like using Dichromate - Sulfuric acid bleaching. The bleach forms Silver Sulfate which dissolves in water and therefore there is image loss. With halide present, this is repressed, but not totally stopped depending on pH and what halide is used.

PE

So would you say the loss is similar to a bleach that has a slight fixing action? (Obviously via a different method).

Personally my biggest concern would be archival quality of the negative, having to colour correct differently to a flexicolor bleach wouldn't be a concern thuogh.

Did Kodak ever try a weak solution of H2O2 + HCl or similar for bleaching?

 

[brucemuir]

Yea, that's my next strategy.
Problem is a lot of the labs around here are also curtailing the color processing they are offering.
I'll figure something out with the help of my friends

I definitely applaud your experimentation attitude and you sharing your findings.
I thank you for that.

 

[Photo Engineer]

I know nothing about image stability in the presence of Copper. All work stopped due to difficulties with the then-current coatings of both film and paper. Archival quality is based, in part, on the final pH as well as "contaminants" and so an acidic bleach may affect the image dye in some fashion. Cyan leuco dye is known to form at acidic pH which then gives the negative an overall red bias when viewed. Copper gives it a green bias, and the overall effect is misleading. We used metal analysis for this work.

A good bleach is Ferric Ammonium Sulfate or Nitrate + a 101% equivalent of EDTA with the pH adjusted to about 6.0. The excess of EDTA is needed to prevent stain from Iron salts and to prevent precipitation of Iron Hydroxides in the Bleach. It would also need some NaBr or NH4Br. This is much stronger than the C41 bleach and more resembles the E6 Bleach.

PE

 

[Athiril]

Yea, that's my next strategy.
Problem is a lot of the labs around here are also curtailing the color processing they are offering.
I'll figure something out with the help of my friends

I definitely applaud your experimentation attitude and you sharing your findings.
I thank you for that.

That should be an advantage, around here labs had to order in 40L quantities minimum iirc, if they are wanting to cut back... they may be happy to split

I know nothing about image stability in the presence of Copper. All work stopped due to difficulties with the then-current coatings of both film and paper. Archival quality is based, in part, on the final pH as well as "contaminants" and so an acidic bleach may affect the image dye in some fashion. Cyan leuco dye is known to form at acidic pH which then gives the negative an overall red bias when viewed. Copper gives it a green bias, and the overall effect is misleading. We used metal analysis for this work.

A good bleach is Ferric Ammonium Sulfate or Nitrate + a 101% equivalent of EDTA with the pH adjusted to about 6.0. The excess of EDTA is needed to prevent stain from Iron salts and to prevent precipitation of Iron Hydroxides in the Bleach. It would also need some NaBr or NH4Br. This is much stronger than the C41 bleach and more resembles the E6 Bleach.

PE

Copper would have to oxidise over time.. apparently its used in marine paints to prevent growths.


Anyway, I've seen somewhere where you say Cyan leuco dye can be removed by some method?

And the final pH should be set by fixer and stabiliser/rinse though?


Also this is interesting - http://en.wikipedia.org/wiki/Red_plague_(corrosion)


edit: The Agfa Vista 200 rolls I had in the fridge expired in only 2009 (I hate wasting 120), so should be pretty decent, shot a whole roll off on tripod with ceiling bounce flash @ EI 200. This should allow me to align flexicolor bleach and copper sulphate and compare, I'll do a test where I apply the same colour correction to both rather than individually.. should allow best to see differences.

 

[Photo Engineer]

The pH of all current color processes is maintained such that it is no lower than about 6.0 at any time (Bleach, Blix or Fix).

The dyes can change color or form leuco dyes if this pH is exceeded either way when the process has ended.

Cyan leuco dye (or any chromogenic dye) can be regenerated by a Ferricyanide bath.

PE

 

[Athiril]

The pH of all current color processes is maintained such that it is no lower than about 6.0 at any time (Bleach, Blix or Fix).

The dyes can change color or form leuco dyes if this pH is exceeded either way when the process has ended.

Cyan leuco dye (or any chromogenic dye) can be regenerated by a Ferricyanide bath.

PE

Guess I'll have to raise the pH a bit then, save some frames for a higher pH bleach test too.

Just potasium ferricyanide on its own?

 

[Photo Engineer]

A leuco dye regenerator is about 50 g/L Potassium Ferricyanide and about 1 g/L NaBr. Treat for up to 10 mins at RT and wash for about 10 - 20 mins at RT, then Stabilize or Final Rinse for about 2 mins at RT. This usually works if it is leuco dye.

The pH of the Ferri solution should be at about 6.5. You may need to treat with a pH 6.5 Na2EDTA solution after the bleach if there is any Iron stain.

PE

 

[Gerald C Koch]

The only time I used a copper sulfate bleach was many years ago. It caused the emulsion to soften so much that it began to come off the backing. This may not be a problem with today's prehardened films, but be careful.

 

[Athiril]

Okay the density problems.. initially I suspected the film.. but then I had some Agfa Vista 200 only expired in 2009... didnt do a sulphite bath... nope not sulphite clearing bath thats causing problems.

Mixed fresh fix.. not fixer, then I suspected contaminated developer... tipped it out mixed up a fresh batch.. nope no problem there.

There I got a bit more suspicious and thought that the CuSO4 bleach may be indeed absolutely terrible and my current mixed up flexicolor bleach in bad shape.. mixed that up from scratch too.... nope!

Only variable left was the film after all.

The Agfa Vista 200 (which I got from the same place as the unknown 400 for 50 cents/roll) expired in 2009... basically 'fresh'.. its in terrible condition for a '09 film. Must have been stored in a baker's oven.


Anyway, just used my last roll of Ektacolor Pro 160 (nice film, but real PITA to load on reels strangely, very difficult to thread, seems to be slightly shorter than normal by a hair, and is stubborn/grips the reel a lot) for the test which I know is good... came out brilliantly... not dry yet though.

Will post one from of that same subject/exposure (flash bounce) from the flexicolor bleach and one from the CuSO4 bleach once dry or after I wake up at least.

 

[Photo Engineer]

Athiril;

Some of the worst keeping of FROZEN color film that I have ever seen was Agfa film. It was beautiful when fresh though! So, maybe you are on to something.

PE

 

[Athiril]

They should have made their film last like one of their developers! Oh well.

I find it strange, I had some Konica 100 and 400 and some german supermarket (re)brand film (Paradies Fotowelt) that were sitting in a hot Aussie pawn shop for a few years, and they all came out fine and were like 1999-2003.

edit: I have some Kodak Gold 100 with the olympics logo on it, 1998-2000 that I think came from the same 'shop'... may have been another though, was at a large camera fair/market/meet.

 

[Photo Engineer]

I have a roll of Gold 400 that is in a special Kodak Park trade dress and was only given to EK people and project members. I also have 2 coffee mugs and some pins given out to project members or for special occasions. I may have to auction them off on APUG someday, proceeds to APUG of course.

PE

 

[Athiril]

Is it magically sharper than Royal Gold 25? Kept only as a secret for those on the inside?

 

[Photo Engineer]

I wish. It is only in a special box.

PE

 

[Athiril]

Flexicolor on the left, CuSO4 bleach on the right.

Density still appears high, and dMax - dMinx needs to be broader/larger (I mixed my own Flexicolor C-41 starter from some old notes and I think I've only put in 1/3rd of the Bromide needed which would explain a lot, but otherwise everything done to these two frames is identical down to the scanning and correcting, only variable is the bleach), but significantly better than the other films I used.

Identical processing apart from bleach.

Scan levels were reset and widened to ensure no clipping, same settings for both. No correction during scan at all apart from inversion (so frames were blue).

Both images put in Photoshop and merged to one layer, black point set to the 'black' box on the card' and white to the white box on the card on the Flexicolor image (left) just to see a general colour correct image with corrections applied to both frames identically, to see difference between the two bleaches in terms of colour.

This test also did not use clearing baths as I was still keeping variables to the minimum for other troubleshooting.

So this is what you might expect from the difference in colour if printing it exactly the same as regular C-41 processed film, or scanned with same settings/colour corrections (eg: A profile set up for x film)


CuSO4 vs Flexicolor Bleach Test #2 by athiril, on Flickr

 

[Athiril]

Used the unknown 400 film again. After pulling my hair out and mixing up all chemicals AGAIN. I used a stop bath straight after development made of apple cider vinegar found in the cupboard at 1+2 (I didn't have anything else.. need some more supplies).


Results are significantly better, dMin is reasonable looking at the histogram but could definately be better, though the image is similar to above.. ceiling bounce flash.. not much of a contrast range in the scene, probably 3 stops at best, so it could probably be lower with a higher range? Something to test. That and it is the crappy unknown brand 400 ISO film, that also I suspect is quite old given where I got it from the place and the date of the other films being sold along with it.



Weird that I never had this problem before, it might be something to do with my water at my new house being pH ~8.5.


Another bleach test will come next week.


edit: Using a blank frame from a lab developed Reala negative, I compared it to blank frames of the cheap 400 ISO negative processed earlier, and then also the cheap 400 ISO negative processed with a stop bath after.

The cheap 400 ISO negative (no stop) blank frame from what I can work out is 0.616 density over the Reala blank frame.
The cheap 400 ISO negative (with stop bath) blank frame is 0.39 density over the Reala blank frame.

And then also compared to one of my Rodinal rehal neg (Pro 400H) which was 0.195 density over the Reala blank frame.