Black and White Reversal Fail

[Athiril]

Success, third time lucky. Fomapan R seem to need a lot (12 min) of bleaching. Know i understand better the process I'll revert to FP4 as I really want to use a 120 film.
Thanks again, will post result when dry.

Just a fyi, don't use the same first development for Fomapan R (at least not at the same time, temp and dilution) as for B&W neg films in reversal process, B&W neg films require significantly more developing action, and potentially a silver halide solvent to help clear the highlights if the developer is not up to maxing out the dMax at the highlights.

Also the only reason I use 27 degrees C for the first developer, is because I like to keep my developing times reasonably short and not go too long. If you want more contrast, you can alter the metol:hydroquinone ratio (ie: less metol to more hydroquinone for more contrast).

I have a first dev formula I use for T-Max that uses the same components, but with added Sodium Thiosulphate crystals.

 

[SMBooth]

Shane if you want I can run you through all my good (and not so) learnings if you want. I'm free evenings mon-fri and most time through the weekend. PM me your number and I'll tee up a time. Needs to be after this coming weekend as out of town presently.

Thanks Andy, I got it sorted now, just need to try with some FP4 or plain jane Fomapan100 in 120. It took me a while to realise what bleached film looked like. I know Athiril note say a longer bleach time need for FomaR but I dint realise how much longer. Most other note say anywhere from 1 -4 min. I needed 12 min. But happy to hook up in late Nov or Dec to fine tune things and get a better understanding how thing change results.

 

[SMBooth]

Just a fyi, don't use the same first development for Fomapan R (at least not at the same time, temp and dilution) as for B&W neg films in reversal process, B&W neg films require significantly more developing action, and potentially a silver halide solvent to help clear the highlights if the developer is not up to maxing out the dMax at the highlights.

Also the only reason I use 27 degrees C for the first developer, is because I like to keep my developing times reasonably short and not go too long. If you want more contrast, you can alter the metol:hydroquinone ratio (ie: less metol to more hydroquinone for more contrast).

I have a first dev formula I use for T-Max that uses the same components, but with added Sodium Thiosulphate crystals.

No, I got that point Athiril, i use same developer but normal temp and times.
If using a normal film do you recommend the same style of first developer, i know your notes were specifically for Formapan R .

 

[Athiril]

This is what I have written down for T-Max 100, the temperatures chosen were just those that didn't give too long developing times. This should work for FP4+, but you'd have to bracket and choose a time and temp and see whether that needs to be increased or decreased for the desired shooting speed. Again you can modify the metol:hydroquinone ratio to change contrast, this may alter developing time for the same film speed though.



Metol 2g/L
Sodium Sulphite 36g/L
Hydroquinone 5g/L
Na2CO3, anh 50g/L
KBr 4/gL
Sodium Thiosulphate Pentahydrate 16g/L

The following times are for undiluted/stock

T-Max 100 @ 200
6 minutes @ 29 degrees celsius

T-Max 100 @ 100
8m 30s @ 24 degrees celsius

T-Max 100 @ 50
7m 15s @ 24 degrees celsius

 

[Europan]

Most other note say anywhere from 1 -4 min. I needed 12 min.

How do you agitate?

 

[Rudeofus]

I know this is slightly off topic, but, is there some alternative to Potassium dichromate or permanganate?
I can easily get ferric chloride (for etching printed circuit boards). Will it be useful as a bleach?

A B&W reversal bleach is a very special animal: it must not contain any silver solvent (or it eats your final image), but at the same time it must provide an anion for bleached silver that keeps it in solution. Ferric Chloride fails in both aspects: it will both dissolve some Silver (both bleached and image silver), but form a poorly soluble salt with the rest.

I wonder whether a Copper Sulfate bleach would work ...

 

[Athiril]

I have found copper sulphate with sulphuric acid to not have any bleaching action on silver in a film.

 

[Rudeofus]

I have found copper sulphate with sulphuric acid to not have any bleaching action on silver in a film.

I remember doing a bleach test once with a Copper Sulfate bleach. It worked quite well for E6 film, but I think I remember it did leave a faint magenta cast in the film. Copper residue is said to be the main issue with this type of bleach, and I didn't pursue this any further. I see no reason why it shouldn't work for B&W reversal, especially in times when Permanganate and Dichromate become harder and harder to obtain.

 

[Athiril]

I have tried it several ways, it simply doesn't work. CuSO4 is +2 and so is AgSO4

 

[pdeeh]

The query about alternatives came from someone for whom obtaining permanganate and dichromate is very difficult.

 

[Rudeofus]

Permanganate bleach works really well, why change it?

A number of issues have been reported or observed by myself about KMnO4 bleach:

• It doesn't last, you always have to mix it fresh.
• KMnO4 dissolves quite slowly, which makes the above issue even more pressing. My first batch of B&W reversal was trashed by undissolved pieces of KMnO4.
• My small container of KMnO4 shows a symbol that indicates that it can go kinetic on you. This makes it both undesirable to stock at home, and more likely to become unobtainium for non-professionals in the foreseeable future.
• KMnO4 is said to weaken unhardened emulsions, so you risk destroying your slides in the process of developing them

It seems to work for many people, but that doesn't mean we shouldn't look for viable alternatives.

 

[pdeeh]

As a matter of interest, what would a sensible formula for a dichromate reversal bleach ?

I've seen a few different versions quoted here and elsewhere, usually 1% dichromate in 1.2% Sulfuric acid.
But my copy of Mason suggests 2.5% dichromate in 2.5% Sulfuric ...

IS there a "definitive" formula or will anything in the range 1%-5% of each do the job well enough?

 

[pdeeh]

But the person wanting to know alternatives isn't in the EU, he's in Peru.

Just because something is easily available in your locale does not mean it is easily available everywhere, and it's extremely misleading to generalise from local situations to other countries.

For instance, the largest (I think) supplier of photographic materials in the UK - Silverprint - will no longer supply dichromate to individuals. To the best of my knowledge, I certainly can't go anywhere and "sign a sheet of paper" to buy permanganate - I have to buy it online.

 

[Photo Engineer]

I have tried it several ways, it simply doesn't work. CuSO4 is +2 and so is AgSO4

Ag = +1, Cu = +1 or +2, SO4 = -2.

If you consider the equation, you must have Cu +2 and this is reduced to +1 in the bleach reaction. The Sulfate must be in excess to carry away the Ag+1 formed during bleaching of Ag metal. Ag2SO4 is water soluble.

Copper blixes and bleaches were considered at EK instead of Iron bleaches, but did tend to leave a stain. If acid enough (thus the H2SO4), it gives an excess of SO4 (good) and acid, which prevents Copper ion from precipitating.

Of course, Permanganate in Sulfuric acid is your second (and only AFAIK) choice.

PE

 

[Rudeofus]

I have tried it several ways, it simply doesn't work. CuSO4 is +2 and so is AgSO4

The typical form of Silver Sulfate is Ag2SO4, not AgSO4.. In fact the latter compound is so uncommon, its existence was first Dead Link Removed, and its synthesis involves compounds that no photographer wants anywhere near ...

BTW the effectiveness of a bleach strongly depends on which anion it provides, and in the case of Copper Sulfate bleach the Sulfate anion alone might simply be too weak. The Copper Sulfate bleach which I tested with E6 film consisted of 100 g/l CuSO4 and 100 g/l KCl, and obviously we can't use this for B&W reversal. It looks like we need a stronger oxidizer than Cu2+, I wonder whether Ferric Nitrate or Ferric Sulfate would work, they're supposed to be stronger than K3Fe(CN)6.

 

[pdeeh]

pdeeh: please read the google book I posted on my previous post. You can find in there a new non-rehalogenating bleach using only persulfate and ferric sulfate in an acidic aqueous environment.

Alessandro, it's quite easy to find these formulae, and I have all the materials I need to hand, but I'm simply pointing out that materials used in some of the formulae are not as easy to find for everybody as they appear to be for you.

I've no idea where an individual in the UK would be able to buy persulfate, for instance. It would probably have to be imported from outside the country

Also, Sigma-Aldrich will only deal with commercial entities, not with private individuals, in the UK and many other territories.

 

[Athiril]

As a matter of interest, what would a sensible formula for a dichromate reversal bleach ?

I've seen a few different versions quoted here and elsewhere, usually 1% dichromate in 1.2% Sulfuric acid.
But my copy of Mason suggests 2.5% dichromate in 2.5% Sulfuric ...

IS there a "definitive" formula or will anything in the range 1%-5% of each do the job well enough?

I think there are alternatives, but probably harder to get.

Any tend to work, so much so, I've eye balled both without measuring, and just leave it in there till complete, it's not like permanganate where it's critical in formula, timing and temperature less you damage your film.


I've gotten permanganate in citric acid to work as a reversal bleach, the citric acid tends to reduce the bleach slowly though, but it works, it takes a long time to bleach though 20+ minutes, and had to change the bleach once to complete it iirc.

Too fiddly and annoying.

Ag = +1, Cu = +1 or +2, SO4 = -2.

If you consider the equation, you must have Cu +2 and this is reduced to +1 in the bleach reaction. The Sulfate must be in excess to carry away the Ag+1 formed during bleaching of Ag metal. Ag2SO4 is water soluble.

Copper blixes and bleaches were considered at EK instead of Iron bleaches, but did tend to leave a stain. If acid enough (thus the H2SO4), it gives an excess of SO4 (good) and acid, which prevents Copper ion from precipitating.

Of course, Permanganate in Sulfuric acid is your second (and only AFAIK) choice.

PE

Cheers, I guess my reasoning wasn't sound late at night

 

[Rudeofus]

Of course we have to deal with reagent availability and cost.
Cerium is outrageously expensive which rules out it's use.

Persulfates: http://www.fisher.co.uk/index.php/e...rchword=persulfate&ordering=&searchphrase=all

AFAIK, Persulfates won't oxidize Silver directly (despite their extremely strong oxidative power), they all need some intermediary to take Silver's electron. The Persulfate ion either oxidizes some other compound which can then oxidize Silver (e.g. persulfate quinone bleach), or it rapidly regenerates the primary oxidizer (e.g. Fe3+, cf. Fenton reaction).

 

[Athiril]

Out of a habit for double checking, I tried a copper sulphate + sulphuric acid bleach on Friday. On a fogged+developed piece of FP4+ in beaker, after 30+ minutes, no change was observed, I left it in there and came back just now (Monday) and have observed the film is clear.

Now I recall leaving processed negs in water for a few days and the silver 'falling off' the film leaving clear film as well, as it could be that, I'm thinking about trying this again and leaving one half of the test strip undeveloped and see if both are removed or just the silver and not the halide.

 

[Rudeofus]

As I said, if you add a suitable anion to your Copper Sulfate bleach, it should work much, much faster. Since B&W bleaches require that the bleached Silver goes into solution, we have no such option here, and it looks like Copper Sulfate bleaches can't be formulated for this purpose.

BTW if you want to test reliably whether all Silver was bleached or whether just the emulsion came off, you could try Selenium toning half of your test clip. I know that thoroughly toned photographic paper won't bleach in a strong Ferricyanide bleach.

 

[pdeeh]

Persulfates: http://www.fisher.co.uk/index.php/e...rchword=persulfate&ordering=&searchphrase=all

Cerium: http://www.fisher.co.uk/index.php/e...?searchword=cerium&ordering=&searchphrase=all

Sorry to bang on about this, but Fisher don't sell to private individuals either.

I'm not asking for any further sources of chemicals, by the way, simply pointing out that it sometimes is quite impossible to buy certain chemicals without making quite extreme and expensive efforts to do so ...

 

[Photo Engineer]

Try Sigma Aldrich.

 

[Athiril]

Sorry to bang on about this, but Fisher don't sell to private individuals either.

I'm not asking for any further sources of chemicals, by the way, simply pointing out that it sometimes is quite impossible to buy certain chemicals without making quite extreme and expensive efforts to do so ...

Silverprint carries potassium permanganate. They also sell potassium dichromate, but can't supply it via the website. "Potassium Dichromate (We cannot sell Potassium Dichromate on the website, but can supply it with an official purchase order. Please see Note on the Raw Chemicals page)".

Contact them to make such an order. I know some random arts & crafts place will have it too.

I also found it here - http://www.georgeweil.com/ProductDetail.aspx?Menu=1&Level1=75&Level2=1146&PID=4513

 

[Steve Roberts]

I'm surprised that (unless I've missed it) no-one's commented on issues surrounding the purchase of sulphuric acid. I've had no trouble buying potassium permanganate online (the last time it turned up from a place only a couple of miles away that I could have walked to!) but I don't know how I'd set about buying the acid. I can't imagine for a moment that anyone would send it through the post. The only way I could think of if I ever felt the urge to experiment was to approach a local supplier of car batteries, though how the quality/concentration of that would compare with what is required in photographic usage I have no idea.
Steve

 

[pdeeh]

Funnily enough that seems terribly easy to buy - B&Q, RObert Dyas etc will have "drain cleaner" which is a strong solution of Sulfuric, or as you say battery electrolyte (many people use that without problems and is marked with the concentration) or of course the ubiquitous eBay. I've got a litre of concentrated sulfuric that I bought online from APCPure - it gets delivered by Parcelforce with suitable hazard labels. I find handling it slightly terrifying tbh