Ferricyanide before Developer

[Peter Rockstroh01]

Does anyone routinely use Ferricyanide bleach before developer to improve contrast and shadow value separation in B&W prints? The impact is amazing, but the process is incredibly sensitive to concentration. While a 1 minute inmersion in a 50ppm solution of Ferricyanide followed by 2 min in Dektol will produce a great improvement, the same test with a 100ppm solution will bleach the image completely. The problem is producing stable and precise solutions, as these dilutions are all one shot.

 

[Donald Qualls]

The reason this is so sensitive is that you're effectively "erasing" the exposure, along with undeveloped fog.

To oversimplify, when silver halide grains are exposed to light, they develop "latent image specks" -- nanoscale specks of metallic silver, directly reduced by light exposure. These specks catalyze the reduction effect of developing agents, so that only halide grains with latent image specks on them will develop.

Your pre-development ferricyanide bath is bleaching (some of) these latent image specks back to effectively unexposed halide, and/or directly dissolving them (if you use a bleach that includes fixer, like Farmer's Reducer). Because these latent image specks are so tiny, there's a very fine line between "improved contrast and shadow value separation" and "no image remaining". There's both very little silver present, and a rather high ratio of reactive area to mass in each individual speck -- hence the small window between "does nothing" and "leaves nothing" in which you're getting an effect you want.

Generally, you'll gain more with less risk of undoing all your dodging, burning, and contrast filtering by developing and fixing, then bleaching as needed to clean up highlights or, as you note, improve shadow values separation.

 

[Peter Rockstroh01]

That clarified the chemistry of FeCn. Thank you. The big difference between bleaching before and after developing, is that bleaching before
acts first and mainly on the shadows, while bleaching after developing acts first and mainly on the highlights. Bleaching an already
developed print removes the same number of units of metallic silver from each area. While the highlights show a notorious improvement
when your remove, lets say, 4 out of 12 silver units, removing the same 4 units from a very dark area won´t be noticed.
I assume that the Ferricyanide has an affinity and reacts first with the heavily energy-loaded image specks, where at low concentrations
the reaction suffocates the active ingredient, showing a stronger effect in shadows than in highlights. Several authors have published on
this technique and I´m attaching David Kachel´s approach. The trick I haven´t mastered, must be preparing the solution of homeopathic
concentration with such consistency and precision that I can print a series of identical copies.

 

[newcan1]

I would not use ferricyanide-bromide bleach this way. It's only going to be of use if the paper is fogged. If it is fogged, treat it with the bleach before even exposing it. And bear in mind that upon treatment, multigrade paper will become single grade.

 

[NB23]

Just be careful not to dip your print directly in the fixer, right from the bleach.

As it happened to me; once I was happy with the bleach look, I immediately dropped the prints in the fixer and Boom! The fixer accelerated the bleaching instead of stopping it. Hours of work vanished right there.

So this is a reminder: after you bleach, wash the prints in water for a few minutes before the final fixing.

 

[mshchem]

That clarified the chemistry of FeCn. Thank you. The big difference between bleaching before and after developing, is that bleaching before
acts first and mainly on the shadows, while bleaching after developing acts first and mainly on the highlights. Bleaching an already
developed print removes the same number of units of metallic silver from each area. While the highlights show a notorious improvement
when your remove, lets say, 4 out of 12 silver units, removing the same 4 units from a very dark area won´t be noticed.
I assume that the Ferricyanide has an affinity and reacts first with the heavily energy-loaded image specks, where at low concentrations
the reaction suffocates the active ingredient, showing a stronger effect in shadows than in highlights. Several authors have published on
this technique and I´m attaching David Kachel´s approach. The trick I haven´t mastered, must be preparing the solution of homeopathic
concentration with such consistency and precision that I can print a series of identical copies.

There's many a printer that uses very dilute bleach and a cotton ball to work on individual prints.
A proper glass medicine dropper, with a black rubber bulb, in the good old days . One drop of water equalled 1/19 - 1/20th of a cc, or in modern 1/19th of a milliliter.
So a liter would contain 19,000 drops. You might go on Ebay or if you have a old drug store and try to find a real non-plastic medicine dropper. If you can find a really old copy of Remingtons Practice of Pharmacy, I have my Dad's, printed in the late 30's the book is enormous, I wouldn't sell it for a thousand dollars. Goes through every thing how to prepare ointments, tintures, all the compounding, vegetable drugs, homeopathic nonsense.

If you could find a proper dropper "USP Medicine dropper" glass with rubber bulb made in the US before 1980.

This sounds fascinating but you need, pure, dry, chemicals. Precise weighing (a old reloading powder scale) or a 10 dollar electronic scale from a coin shop. Fit in the palm of your hand.

 

[AgX]

This sounds fascinating but you need, pure, dry, chemicals. Precise weighing (a old reloading powder scale) or a 10 dollar electronic scale from a coin shop. Fit in the palm of your hand.

One should be very considerate with such cheap scales. They typically do not indicate their error, nor a minimum load. Best avoid any metering in the decimal range. Thus prepare a solution in a way that one can except sufficient precision at the scale and the graduated cylinder. For homeopathic amounts then use a micropipette fed with that solution.

As one then has a large stock solution, this again should be stable with no chemical disintegration over time, or to be disposed.

 

[grain elevator]

There have been heated discussions about it here, for example https://www.photrio.com/forum/threads/slimt-and-why-you-should-be-using-it.64135/ . Maybe people with strong opinions on it are too war-weary to come out of the woodwork now. You'll find more if you search the forum for SLIMT.

 

[Peter Rockstroh01]

I would not use ferricyanide-bromide bleach this way. It's only going to be of use if the paper is fogged. If it is fogged, treat it with the bleach before even exposing it. And bear in mind that upon treatment, multigrade paper will become single grade.

Thanks for your comment. Why and how will bleach turn multigrado into single grade paper ?

 

[Peter Rockstroh01]

Just be careful not to dip your print directly in the fixer, right from the bleach.

As it happened to me; once I was happy with the bleach look, I immediately dropped the prints in the fixer and Boom! The fixer accelerated the bleaching instead of stopping it. Hours of work vanished right there.

So this is a reminder: after you bleach, wash the prints in water for a few minutes before the final fixing.

Thank you ! Now I understand at least one of the images I lost.

 

[Peter Rockstroh01]

Thank you all for your comments. It seems to be a useful tool for certain images, although not something I would plan to use as SOP.
Looking back at my images from 20 years ago, I took and printed heavier and darker than today and this method looks like an
interesting approach to improve those photos. If I find a consistent and predictable method to improve those photo, I´ll post them here.

 

[Alan9940]

I have used Mr. Kachel's SLIMT technique for paper on both Adox Lupex and Ilford Ilfobrom Galerie with great success. However, I find the general dilution and time recommended for paper to be too strong and fast acting for me. I will say that I've only ever used it to reduce contrast by, at most, one-half grade. Once you get a dilution/time dialed in that provides the results you're looking for, it's a nice additional tool in your arsenal.

 

[john_s]

One should be very considerate with such cheap scales. They typically do not indicate their error, nor a minimum load. Best avoid any metering in the decimal range. Thus prepare a solution in a way that one can except sufficient precision at the scale and the graduated cylinder. For homeopathic amounts then use a micropipette fed with that solution.

As one then has a large stock solution, this again should be stable with no chemical disintegration over time, or to be disposed.

I will not use a cheap electronic balance without checking it with some calibration masses ("weights"). The only chemical that I need to weigh small quantities of is phenidone, and the stock solution does not work well there (some people have had success with some solvents I know).

 

[Donald Qualls]

FWIW, phenidone keeps well as a 1% (10g/L) solution in 91% isopropyl alcohol (likely also true in similar strength ethanol, though denaturants add an unknown to the formula). It does not keep well in a water solution, or in other solvents that contain much water, from what I recall. The isopropyl is, like most short-chain alcohols, completely miscible with water, and with the phenidone already dissolved in the alcohol, there's no fuss getting it dissolved. Some developers (like H&W Control) have carried suggestions that the phenidone not be added to the developer as such, but rather the correct amount of 1% phenidone in 91% isopropyl be added immediately before use.

 

[john_s]

Donald, I have read this and have done it with ethanol (food grade) without success. Someone suggested propylene glycol. I will stick with adding the powder (actually Dimezone-S which probably dissolves more easily)

 

[Donald Qualls]

Donald, I have read this and have done it with ethanol (food grade) without success. Someone suggested propylene glycol. I will stick with adding the powder (actually Dimezone-S which probably dissolves more easily)

What percentage strength of alcohol? Yes, it's much more expensive than solvent grade (or even ordinary vodka or double strength vodka), but a bottle a year is more than you'll need for your darkroom unless you're shooting a lot more film than my budget will take. Ordinary vodka is 60% water by volume. Double Tvarscki, if you can get that, is only 20% water, and that's still too much. From what I understand, it's water that causes the problems with keeping; you need your alcohol to be 90% or higher (95% if you can get it -- Everclear should work as a 95% food grade ethanol, if they sell it where you are).

Dimezone-S was specifically chosen for a lot of developers because it works almost identically to phenidone, and is much more easily soluble in water. If that's what you have, it should sub perfectly well for phenidone in any formula, and not need to be stored as an alcohol solution.

 

[john_s]

It was over 90% alcohol.

 

[Donald Qualls]

It was over 90% alcohol.

Okay. There must be something more to this than I understand. As I note, I have used phenidone (not dimezone-S) as 10 g/L solution in 91% isopropyl for addition to H&W Control no-phenidone stock solution, and it kept for at least several months before I used it up.

 

[Bormental]

Very interesting! Having read @Donald Qualls explanation I must ask: what's the advantage of doing this instead of just reducing exposure? The OP cites enhanced contrast, but that can be controlled by development time and agitation.

 

[Donald Qualls]

According to the OP, it seems like this is more or less the opposite of preflashing. Post-exposure bleaching, it's claimed, cleans up hightlights at the same time it enhances shadow contrast, while preflashing enhances highlight contrast with little effect on shadow values.

I'm inclined to believe the same or very similar effect can be had with careful split-grade printing -- but clearing out detail from highlights would usually seem opposite to what I want in a print; for most subjects I'd rather compress the dynamic range to avoid either highlight or shadow areas devoid of texture.

 

[Raghu Kuvempunagar]

Very interesting! Having read @Donald Qualls explanation I must ask: what's the advantage of doing this instead of just reducing exposure? The OP cites enhanced contrast, but that can be controlled by development time and agitation.

You may want to read David Kachel's detailed exposition on SLIMT and also @Doremus Scudder's insightful posts on the same.

 

[Anon Ymous]

Donald, I have read this and have done it with ethanol (food grade) without success. Someone suggested propylene glycol. I will stick with adding the powder (actually Dimezone-S which probably dissolves more easily)

I still use a 1% phenidone in propylene glycol solution that I mixed back in 2016...

 

[john_s]

I still use a 1% phenidone in propylene glycol solution that I mixed back in 2016...

That's promising. Does it absorb moisture from the atmosphere? If so, maybe a little doesn't matter.

 

[Anon Ymous]

That's promising. Does it absorb moisture from the atmosphere? If so, maybe a little doesn't matter.

I honestly don't know, but doesn't seem to matter anyway. I store mine in a tightly capped glass bottle, so it doesn't really have much of a chance.

 

[newcan1]

Thanks for your comment. Why and how will bleach turn multigrado into single grade paper ?

Because the multigrade quality of the paper is dependent on dyes within the paper separating how the exposure affects two different layers within the paper. The water in the bleach will dissolve away those dyes.