Reversal print processing video..new approach

[DonF]

+1 !

really great stuff you have been doing, and it seems a bit less finicky than tintypes ( either wet or dry )

Definitely less finicky with some of the slow-speed and creative appeal of dry plate. Being able to meter reliably is a definite plus! Safelight processing is nice. Paper is really cheap. Shooting 10 exposures with our five unmodded film holders without a trip back to the darkroom is a luxury!

Don

 

[Joe VanCleave]

I haven't posted in some time, but have been conducting numerous experiments. I've been attempting to reduce the variability in the process, by using a one-shot developer and bleach. Here are the details of today's experiments:

Image 1:
Paper: Arista grade 2 RC, semi-matte finish. Rated ISO=0.8. Exposure = 1/4sec @ f/5.6. Developed in Ilford Universal paper developer diluted 1+10 (100mL H2O + 10mL concentrate). Developed to "completion", i.e. 5 minutes. Bleach: 4.5% solution (100ml H2O + 15mL of 35% H2O2 +1 TSP citric acid, for 45 minutes). Second exposure under enlarger until midtones appear. Result:

Reversal001 by Joe Van Cleave, on Flickr

The print looks pretty good, except for the center 3rd being lighter than the outer 3rds. This was a one-shot process, the next print used fresh chemistry.

Image 2:
Paper: Arista grade 2 RC, semi-matte finish. Rated ISO=0.4 (3 stops over ISO3 - it was later in the afternoon, less UV light, hence more exposure). Exposure = 1/2 second @ f/5.6. Developed in Ilford Universal paper developer diluted 1 +10 (100mL H2O + 10mL concentrate). New one-shot batch. Developed to "completion", i.e. 5 minutes. Almost black coming out of first developer. Bleach: 9% solution (100mL H2O + 25mL H2O2 + 1 TSP citric acid). Second exposure under enlarger until the midtones appear. Result:

Reversal002 by Joe Van Cleave, on Flickr

The print appeared totally black coming out of the first developer. After bleaching, the center 3rd was cleared white but the outer 3rd on each side appeared uncleared. Not sure why. I'm using 5x7 trays, so the liquid level was rather low. I agitated continuously. I'm attempting to use these chemicals as a one-shot process, to reduce variability caused by chemical exhaustion. But somehow the center 3rd cleared. I had the print face-up in the tray, continuous agitation, ensuring the paper was immersed in liquid. The paper's natural curl means the center was closer to the surface, more shallow chemical. Yet the center cleared better than the edges. Another mystery I can't explain. Why would the center clear better than the edges when it was immersed less in the bleach?

Later, I made another exposure at ISO 0.8, new one-shot developer of 200mL H2O + 15mL concentrate, then the bleach at 200mL H2O + 50mL H2O2 + 2 TSP citric acid, for a concentration of 9%. Bleached for several hours. The print didn't clear, it's mottled badly. I doubled the volumes to compensate for any agitation issues from minimal volumes. Fresh chemistry, temperatures constant. Constant agitation for the first development. Agitated in the bleach numerous times, flipped front and back sides up. Nothing seems to help. I'm leaving the print in the bleach overnight to see what happens.

My conclusion thus far is that the way I'm doing this process is unmanageable. Not able to repeat two prints with the same result, exposed identically in-camera within a minute of each other; each print processed identically with fresh chemicals, constant darkroom temperature, same dilutions, etc. I'm seriously considering giving up on this process. I can't figure out where the uncontrolled variability is coming from. I've been working in the darkroom for +25 years, always have had good darkroom discipline, can make great paper negatives. There's something going on with this process that I don't understand. Help needed.

EDIT: On the second print, note the two vertical scratches near the middle of the image. I've seen these in several prints. I'm good with darkroom discipline, developing these one at a time, using tongs to handle the paper. I'm suspecting this new batch of paper I recently ordered from Freestyle Photo has scratches from the manufacturing process.

 

[Joe VanCleave]

On a positive note, the first image shows no sign of mottling in the highlights. I developed to completion on the first development, then ensured adequate exposure under the enlarger for the second exposure, on the theory that the highlight mottling I've seen before is inadequate development of the highlights from the first step. This seems to confirm that theory.

The single biggest issue remaining is the huge variability in bleaching, using fresh chemicals mixed identically, at the same temperatures. Obviously the process needs adequate exposure and development in the first step, else the highlights won't bleach properly.

I've tried mixing the bleach two ways: adding the citric acid to the H2O first, then adding the H2O2; and adding the citric acid to the already diluted H2O2. Still not able to get repeatable results using identically exposed negatives.

I also don't have a good understanding of how much citric acid to add to a given quantity of peroxide at a particular dilution. Perhaps I need a pH meter. Does too much CA:H2O2 cause one problem, like mottling, while too little CA:H2O2 cause inadequate bleaching? Not certain. The process seems to have an extraordinarily narrow sweet spot. Unmanageable by my experience thus far.

I'd like to make this process work, but am not certain how to proceed.

 

[Gerald C Koch]

Hydrogen peroxide is not toxic. The 3% strength diluted 1+1 is used as a mouth rinse particularly for gum disease. However the 35% can cause serious chemical burns if it contacts the skin. This is in addition to causing fires if it contacts organic materials.

 

[DonF]

Joe, thanks for publishing these latest tests. The unbleached areas on the prints look a lot like the mottled patches on the last portrait shot I posted. These were due to first developer underdevelopment, as I mentioned.

I am using Dektol at twice the normal 1+2 concentration (1+1). I wonder if a stronger concentration of developer would help. I read that reversal processing of films often uses some potassium thiocyanate or hypo in the first developer only to "remove excess silver halides". I also read that use of a stronger developer and longer development times reduced or eliminated the need for the solvent.

I tried using 1+3 Dektol early in my dichromate bleach tests. All the prints came out with the same uneven cast shown in your last examples. Just a thought.

I have some concentrated Phosphoric Acid I was going to try with the peroxide, diluting for a similar ph (2.0 ???), but am uncertain of the role of citric acid in the chemical reaction in the bleach, so there may be more involved than simply lowering ph.

Regards,

Don

 

[himself]

Hey Joe,

thanks for the update!

It's interesting that you're not getting consistent results. To preface this I'll say that I'll admit to sometimes being a bit sloppy in the darkroom (reusing old dev, bleach until it appears not to work, and never as one-shot) - but I'm getting fairly consistent results from the process.. that's not to say consistently good - some, as I've posted before, have been consistently awful, but as long as my process has been the same, the results have been similar for those conditions.

one thing I did notice is that while I was working through the strips I was cutting off the same image, and as those strips got smaller, it was getting harder to bleach them evenly - even if they looked even (basically the strips would float). So maybe, if you want to continue experimenting, I'd ditch the one-shot and go for a higher volume of bleach, more even than the "normal" standard of dev for that size paper.

also, a thought has just occurred to me, can you buy your peroxide at a lower %, rather at a higher concentration and then diluting it yourself, could your water be effecting the final solution somehow?

best,
dafydd

 

[Joe VanCleave]

Don: Thank you for your feedback. I used the Ilford concentrated liquid developer at a strength of 1:10, which is more concentrated than I've used in the past. I also developed it for 5 minutes, which is intended to develop to completion. I could use an even stronger solution, perhaps.

Regarding the role of citric acid, somewhere I read that it combines with the silver to form silver citrate; the role of the peroxide is to help the citric acid and silver to combine through some ionic bonding ... I'm not a chemist, so this is mere layman's understanding.

Dafydd: There's something mysterious going on with this process, for certain. I've found that if the print doesn't begin to bleach within a minute or two, it doesn't seem to matter if you add more peroxide and/or citric acid. The latest test from last night was a total failure, the print was very dark coming out of the first developer, but the center of the print lightened somewhat in the bleach, with the rest of the print still dark. After the second exposure and development there was not evidence of the original image, just a mottled mess and the middle third lighter than the edges. I have another print exposed at the same time from yesterday that I'll try processing this morning.

Your thoughts regarding water quality are worth considering. I'll try using distilled water for the bleach solution.

The unevenness of yesterday's results could be related to the low volume of chemistry in the trays. Perhaps there is some minimum quantity of active chemical required for a certain surface area of paper. I'll try using the 300mL volume like I started with several weeks ago, and use the 9% concentration by using a 1:4 ratio of 35% H2O2 to water. Still not certain how much citric acid to use. I'll use 1 teaspoon for every 100mL of solution and see what happens. If this works, it means using 75mL of 35% H2O2 for every 4x5 print. A bit costly and wasteful of chemicals, but perhaps that's what this process requires. I'll keep you updated.

 

[DonF]

I wonder if using a traditional stop bath might help. Could the higher ph of the developer be affecting the action of the low ph bleach? I have been using a weak Kodak acetic acid indicator stop bath.

 

[nmp]

This might be useful, if not seen already...

http://www.filmlabs.org/docs/citric-hydrogen-peroxide-bleach.pdf

:Niranjan

 

[himself]

The latest test from last night was a total failure, the print was very dark coming out of the first developer, but the center of the print lightened somewhat in the bleach, with the rest of the print still dark. After the second exposure and development there was not evidence of the original image, just a mottled mess and the middle third lighter than the edges.

that does sound really quite strange.

the final image I posted (an 8x10) was bleached in only 300ml 12% peroxide + 2 tspns citric acid with constant agitation. It didn't bleach perfectly (because it had become weaker after test prints), but it was even. So it seems like your 200ml in 5x7 should be enough. Besides, if it weren't, wouldn't the centre bleach less because of the bow of the paper?.. having said that, looking again at the first image in post #77, it looks like the ends have lifted and the liquid has settled in the middle.

could it be that some papers work better than others? I've had a similar problem with Lith, where the centre of the paper didn't develop as well as the edges.

 

[Joe VanCleave]

Today I decided to increase the volumes of the developer and bleach to 300mL. The developer was 300mL H2O + 30mL Ilford concentrate. Bleach was 225mL distilled water + 75mL 35% H2O2 + 3tsp citric acid (about a 9% concentration of H2O2).

Based on the prints attempted yesterday and last night, I had a hunch that my assumed paper speed of ISO 0.8 was just too much, the bleach couldn't clear all that silver, hence the mottled appearance. So the two prints attempted today were at ISO 3 & 6, exposed in-camera within seconds of each other. My experience of using the glossy version of this Arista grade 2 RC paper is that it's faster than Ilford multigrade RC paper (I've used it at ISO 12 for paper negatives).

ISO 3 print: exposure = 1/15s @ f/5.6. Subject was daylight landscape of my front yard. Developed for 3 minutes. My darkroom had a space heater running to ensure temperatures were in upper 60's F. Chemical temps were also checked in the trays with a thermometer. Post the first developer the image had discernible shadows near paper white, with highlights very dense. The rinse step between the first developer and bleach was 400mL H2O + 2 tsp citric acid. Bleaching was face-up, continuous agitation for first 5 minutes, then periodically until image was as bleached as it would get, about an hour's duration. I used a black tray covered with another, larger black tray face down, so I could exit the darkroom without fogging the print. Post-bleaching the image was very faded, bleached highlights a cream color, barely discernible midtones in some areas. Thorough water rinse, squeegee front side, then second exposure was under enlarger, 16" height at f/22 for about 30 seconds, or until some tone began to appear in previously unexposed areas of print. Second development for about 2.5 minutes or until shadows were stable.

Reversal003 by Joe Van Cleave, on Flickr

The center of the image, where the path is located, is bleached much more, the tones also more neutral gray. I suspect this was from the paper curl, being face up in the tray, the center of the paper was closer to the surface. Note the tong mark upper left edge, and scratches upper right. Not certain where scratches are occurring. I use the same tongs for the same trays, perhaps some residual contamination. Need to rinse tongs between steps.

ISO 6 print: exposure = 1/30s @ f/5.6. Same processing as above, in same chemicals (not replenished). I weighted down both long edges of the print in the bleach with thin strips of glass (leftovers from a stained glass project - I figured the glass would be somewhat chemically neutral). Bleaching much more even, though there's some brown tones in part of the sky at upper right. No scratches seen. Note tong mark again upper middle.

Reversal004 by Joe Van Cleave, on Flickr

Going forward, next week I'm going to repeat these steps, at ISO 3 for daylight landscapes. No more than two 4x5's for 30mL of developer concentrate, 75mL of 35% H2O2 and 3 tsp citric acid. I need to prove the results are reliable before attempting 8x10's.

I contacted Ricardo Leite, the author of this process mentioned in the link above, and he suggested acetic acid is a better, more stable choice than citric acid, because the citric acid tends to break down the peroxide over time. I'm going to try this next week, also.

~Joe

 

[Joe VanCleave]

The phenomenon of the center of the print bleaching faster than the sides has me intrigued. It seems to be because the paper is closer to the surface, perhaps with less volume of chemistry to replenish the reaction. Is it due to some oxidation due to proximity to the surface? Is there some natural restraining action happening between various chemical reactions? Whatever the cause, it has me thinking (and hoping) that this could lead to a process change that uses less volume of chemicals with a better end result. Perhaps weigh all four sides with thin strips of glass, then pour only as much chemicals to cover the glass.

I'm also excited about trying this with acetic acid instead of citric acid. Ricardo, in his email reply to me, indicated that the pH needs to be around 2.

~Joe

 

[Joe VanCleave]

This Arista RC grade 2 semi-matte finish looks lovely in person, a wonderful smooth sheen with the warm tones from this process. I like the look, and convenience of quick rinsing and drying, better than the fiber glossy Harman DPP.

If I repeat this experiment with 8x10's, logic would dictate quadrupling the volumes (because of 4x the surface area) with the same concentrations, which would imply 120mL of developer concentrate and 300mL of 35% peroxide for each print - a lot of chemical usage for one print. However, given that today's experiment showed I can get at least two 4x5's from this quantity, perhaps I'll just double the volumes for 8x10's and see what happens. What's the worse that could happen? Answer: waste paper at 4x the cost, that's what!

~Joe

 

[NedL]

FWIW, mine always seem to bleach from the center, with a strip in the middle bleaching first and the edges finishing last. I have several times used acetic acid stop prior to bleaching, but am worried that carryover could form peracetic acid and harm the gelatin. When I did use the acetic stop, I rinsed well before bleaching. Now I'm using weak citric acid ( ~ 0.5% ) stop prior to bleaching and no rinse between. I think I've seen indications that the bleaching will slow or even stop with too much citric acid added. A tentative non-chemist hypothesis/guess is that too much citric acid lowers the pH too much, so that the H2O2 becomes too strong an oxidizer and there is not enough citrate ion to keep up.

Also, without using stop, even with some rinsing, the initial bleaching can start very fast ( easily visible in the first 30 seconds ) accompanied by fizzing. I think this is related to some tiny bubbles or blisters that are visible in dark areas of the final print. These blisters went away when I started using stop before bleaching... and so did the fast initial bleaching and fizzing. In fact, the first time I tried it, I thought the bleach wasn't working because the progress was no longer soon visible, but it did work when left an hour or two.

There is something delicate about the process during the bleach ( maybe it is a thin film of Ag Citrate on the surface? ) and it is susceptible to scratches or fingerprints...anything that touches the surface will leave a white mark on the final print.

I can tell by reading that we are all approaching this somewhat differently ( type of paper, amount of 1st exposure, development, w or w/o stop, bleach H2O2 and CA concentrations and time, amount and contrast filtering of re-exposure )... so we should be cautious about generalizing. I think I'm at a repeatable process... but I suppose I could have had a run of luck that will run out!

 

[Joe VanCleave]

I think my early experiments saw immediate bleaching within the first minute, but not in these last few weeks. Perhaps I'm using too much citric acid. What I should do is start with a very small quantity, then have a ready supply of pre-dissolved citric acid solution, to add to the bleaching agent if things are going too slow. Like titrating in a bit at a time, with good agitation, with the print temporarily removed.

 

[NedL]

That's pretty similar to how I started. I keep an eyedropper bottle of 20% CA here for various things, and I used that and added a small amount ( < 1 ml ). Later I added more bit by bit and noticed the bleaching went a little faster each time. When I switched to using dry CA ( my eyedropper ran out! ) I started at a point about twice as concentrated, and it didn't speed things up much if at all... then I tried one with twice as much CA and it failed completely. Right now I'm using 0.4 grams of CA in 120 ml of 3% H2O2, and it's taking between 1 and 2 hours to bleach completely. Every one I've made so far was either 5x7 or 5x8 inches.

Hopefully I'll make some more soon, things have been chaotic here lately.

 

[nmp]

There is something delicate about the process during the bleach ( maybe it is a thin film of Ag Citrate on the surface? ) and it is susceptible to scratches or fingerprints...anything that touches the surface will leave a white mark on the final print.

More likely that it is the peroxide that is the culprit for softening/degradation of the gelatin. After all it is the active ingredient in the so-called etch-bleach process. It is also the basic component in the Mordançage process that involves messing up the gelatin layer.

:Niranjan.

 

[nmp]

A patent that describes the mechanism behind the use of citric acid this way:

All photographic bleaches are solutions of oxidizing agents capable of converting metallic silver to silver ions. Specifically, the oxidizing (bleaching) agents convert silver from an oxidation state of zero (silver metal) to silver in an oxidation state of +1. Simultaneously, the oxidizing agent is reduced. As discussed by Levenson in the cited reference, the oxidizing power required of the bleach may be quantified in terms of an electrochemical potential whose value depends on the concentration of free silver ions in the material being bleached. The higher the free silver ion concentration, the greater the oxidizing power required of the bleaching agent.

After chemical development, silver is present in a photographic material as metallic silver and as undeveloped silver halide. Since the solubility of each of these materials is negligible in water, the concentration of free silver ions in the material is negligible, and bleaching will begin if the material is exposed to a bleach solution containing even a weak oxidant. As the oxidation of metallic silver proceeds and free silver ion increase, the electrochemical potential needed to continue silver oxidation increases. Only bleaches containing oxidants with very high electrochemical potentials will be able to oxidize all of the metallic silver in a developed photographic material in the presence of the free silver ion products of bleaching. A table showing the electrochemical potentials of oxidants useful in photographic bleaches is given on page 448 of the Levenson reference. If the level of free silver ion is kept low, oxidants of weaker oxidizing power are useful in photographic bleaches. One way to maintain a low concentration of free silver ion in a bleaching photographic material is to include in the bleach composition chemical species that will combine with free silver ion as it is generated by the oxidation of developed (metallic) silver.

more at : http://www.google.co.in/patents/US5641616

:Niranjan.

 

[DonF]

Based upon my Chem 101 course-level understanding, the bleach (Peroxide, Dichromate or Permanganate) oxidizes metallic silver into silver ions. The bleach alone will work until the solution becomes saturated with ions. Adding a reducing agent (like sulfuric acid, phosphoric acid or citric acid) removes the silver ions from the solution and produces soluble silver compounds that are not light sensitive and can be washed away. It also allows more silver to be oxidized into silver ions by removing those ions from the solution.

Something like that?

The patent is actually very instructive. The background section gives a very readable explanation of the bleaching process.

Don

 

[DonF]

More likely that it is the peroxide that is the culprit for softening/degradation of the gelatin. After all it is the active ingredient in the so-called etch-bleach process. It is also the basic component in the Mordançage process that involves messing up the gelatin layer.

:Niranjan.

Potassium permanganate bleach has a reputation as well for softening or even dissolving the emulsion if left in too long.

The Potassium Dichromate bleach actually has a hardening effect on the emulsion, a good thing.

Don

 

[nmp]

Based upon my Chem 101 course-level understanding, the bleach (Peroxide, Dichromate or Permanganate) oxidizes metallic silver into silver ions. The bleach alone will work until the solution becomes saturated with ions. Adding a reducing agent (like sulfuric acid, phosphoric acid or citric acid) removes the silver ions from the solution and produces soluble silver compounds that are not light sensitive and can be washed away. It also allows more silver to be oxidized into silver ions by removing those ions from the solution.

Something like that?

The patent is actually very instructive. The background section gives a very readable explanation of the bleaching process.

Don

Yeah, that sounds about right. You can look at it as an equilibrium reaction. Initially there is are no products so the forward reaction is the dominant one. As more ionic Ag forms it can revert back at a finite rate until the backward and forward rates are equal, at which point no more bleaching occurs. Then using the LeChatelier's principle, if you remove any of the products, the reaction can be pushed forward. That is what citric acid would do by forming solid Ag citrate and taking the ionic Ag out of the solution, so the peroxide can oxidize more of the silver metal. I guess one can not increase the citric acid content of the bleach in an unlimited fashion as the oxidation reaction then will become kinetically suppressed by reducing the accessibility of the Ag to fresh peroxide. Thus, there is probably an optimum ratio of the peroxide to citric acid in the starting formula.

Silver citrate has a low solubility in water so it won't be washed out in the post bleach wash step. It will require the fixer to finally take it out of the paper. It is also photosensitive but mostly to UV. My guess is it does not appreciably convert to silver during the second exposure with a normal lamp to re-darken those areas. Or does it? If it does, then using a bulb that has a very low UV component might be helpful. Sunlight exposure, not so.

:Niranjan.

 

[NedL]

Based upon my Chem 101 course-level understanding, the bleach (Peroxide, Dichromate or Permanganate) oxidizes metallic silver into silver ions. The bleach alone will work until the solution becomes saturated with ions. Adding a reducing agent (like sulfuric acid, phosphoric acid or citric acid) removes the silver ions from the solution and produces soluble silver compounds that are not light sensitive and can be washed away. It also allows more silver to be oxidized into silver ions by removing those ions from the solution.

Something like that?

The patent is actually very instructive. The background section gives a very readable explanation of the bleaching process.

Don

Yes except that I don't think the reducing needs to produce soluble silver compounds, only non-actinic. In your dichromate bleach, the silver sulfate is soluble ( in sulfuric acid ) and being washed away. I suspect in the H2O2 process, the silver citrate is formed in the paper and removed later by the final fixing step. And I suspect this is the main reason the two processes behave somewhat differently. It's even possible that something complicated is happening during re-exposure: it could be that some of the silver citrate can contribute silver to the freed-up Br, forming new light sensitive AgBr.

Edit: Niranjan and I were typing at the same time, but I see he's thinking along the same lines I am.

 

[removed account4]

LOL im glad you guys have a clue what is going on
im just doing it without much attention to the mechanics of
how and what is dissolving and changing something else ...
i've been rather busy the past couple of days but tomorro i might
have a free bit of time to fiddle around a litte more ...

 

[nmp]

LOL im glad you guys have a clue what is going on
im just doing it without much attention to the mechanics of
how and what is dissolving and changing something else ...
i've been rather busy the past couple of days but tomorro i might
have a free bit of time to fiddle around a litte more ...

I am on the opposite side of John....trying to understand a process that I might probably will never do myself.

 

[DonF]

Yeah, that sounds about right. You can look at it as an equilibrium reaction. Initially there is are no products so the forward reaction is the dominant one. As more ionic Ag forms it can revert back at a finite rate until the backward and forward rates are equal, at which point no more bleaching occurs. Then using the LeChatelier's principle, if you remove any of the products, the reaction can be pushed forward. That is what citric acid would do by forming solid Ag citrate and taking the ionic Ag out of the solution, so the peroxide can oxidize more of the silver metal. I guess one can not increase the citric acid content of the bleach in an unlimited fashion as the oxidation reaction then will become kinetically suppressed by reducing the accessibility of the Ag to fresh peroxide. Thus, there is probably an optimum ratio of the peroxide to citric acid in the starting formula.

Silver citrate has a low solubility in water so it won't be washed out in the post bleach wash step. It will require the fixer to finally take it out of the paper. It is also photosensitive but mostly to UV. My guess is it does not appreciably convert to silver during the second exposure with a normal lamp to re-darken those areas. Or does it? If it does, then using a bulb that has a very low UV component might be helpful. Sunlight exposure, not so.

:Niranjan.

Great stuff, Ed and Niranjan. That all makes perfect sense.

I was thinking of trying some phosphoric acid (I have some 35% on hand for making acid phosphate old fashioned beverage "phosphate soda" additive) to replace the citric. I read that the acid in a non-halogenating simple bleach needs to be non-organic, which rules out acetic acid, but phosphoric is a mineral acid, like sulfuric. Would the reduction reaction with phosphoric acid form a fixable or washable silver compound?

Best,

Don