Reversal print processing video..new approach

[DavidJRobertson]

Might be interesting to try using EDTA instead of citric acid. Both are chelating agents, but EDTA is a much more powerful chelating agent. EDTA (Ethylenediaminetetraacetic acid) is fairly widely used, non-toxic and can be bought on eBay among other places.

EDTA (disodium salt) + H2O2 definitely works as a bleach but I haven't tried using it as part of a reversal process.

 

[NedL]

and it's often listed as an H2O2 stabilizer.

 

[bernard_L]

Please let me intrude into this thread, as an onlooker.

• Congratulations to the recurring contributors, both for their systematic and persistent work, and for producing a truly informative thread (as opposed to so many threads that are just exchanges of opinions).
  
• Now I'm tempted to try in-camera positives myself. But I think I'll go the dichromate route: from what I see it gives readily and consistently nice results, while the peroxide process seems to be a never-ending challenge (well, maybe some like the challenge?).
  
• I guess some of you want to stay away from dichromate because of toxicity. When I used dichromate for intensification, and before discarding the used solution, I "neutralized" it by adding sodium sulfite to convert Cr(+6) to Cr(+3) (green). If I do my sums right, one mole of potassium dichromate (294g) releases 6 electrons when the Chromium is reduced to the (+3) oxidation state. Each mole (126g) of sodium sulfite accepts 2 electrons being oxidized to sulfate, so one needs 3 moles (378g) of sodium sulfite for each mole (294g) of potassium dichromate, i.e. 1.285:1.00. Including some margin, and easy to remember: sulfite 1.5 times the mass amount of dichromate. As for toxicity, I have next to me a package of good ol' ID-11; the USA safety warning is terrifying: "harmful... allergic skin reaction... serious eye damage... genetic defects... cancer... damage to organs...".
  Seriously, when handling dichromate, I avoid sneezing and wear gloves.
  
• I've seen a passing mention of multigrade paper being too contrasty. I've had the same issue in my limited incursions into pinhole photography with paper negatives. As mentioned, grade paper is a possibility. I used, with multigrade, a yellow filter (gel) taped permanently behind the pinhole.
  
• And, if I would be allowed a dumb question, why cannot one use, in reversal processing of paper, just pot ferricyanide + pot bromide? Certainly there is a reason, and I hope a distinguished chemist might explain.

 

[Anon Ymous]

You can't use a ferricyanide + bromide bleach, because it's a rehalogenating one. It means that it converts metallic silver back to the silver bromide form it came from. If you do use it, then you'll get a totally black image as a final photo.

 

[bernard_L]

You can't use a ferricyanide + bromide bleach, because it's a rehalogenating one. It means that it converts metallic silver back to the silver bromide form it came from. If you do use it, then you'll get a totally black image as a final photo.

Duh! thank you.

 

[himself]

Please let me intrude into this thread, as an onlooker.

• I've seen a passing mention of multigrade paper being too contrasty. I've had the same issue in my limited incursions into pinhole photography with paper negatives. As mentioned, grade paper is a possibility. I used, with multigrade, a yellow filter (gel) taped permanently behind the pinhole.

Hi Bernard,

I think it was me that brought this up, but since then I've been doing some research and it looks like the Ilford MG I'm using is supposed to be grade 2 when used without any filters, and as it appears to be hard (here at least) to get graded paper lower than that anyway, I've decided to stick with the graded paper and try to control the contrast with filters as you've done in the past.

It should be possible to get it down to grade 0 (or the equivalent) with filtering, but given the (very low) asa rating of the paper it will depend on how much exposure compensation would be needed too.

It's definitely an interesting technique to use, and I would recommend trying the peroxide just for sake of it.

 

[himself]

I've been working on a different project over the last week, but I've also been thinking about the potential of this and I've had some thoughts on further ways I'd like experiment further.

So first, I have some old Ilford glass plates I've been wanting to use and was wondering if it were possible. Obviously the easiest way is to just do it, but before I do I'd like to have some sort of ballpark rating for the first exposure. It looks like, thanks to Joe, that we're all rating the paper 3 stops slower than we would be if we were using it for paper negs, so with that in mind, should I just go for 3 stops on top of what I'd rate the plates (previous experiments) when used as negatives?

And so secondly, which might be less predictable, what do you all think of the idea of using a lith developer for the second development (using a lith-able paper)? There are a few more variables I guess, but I was thinking that because of the extra exposure needed when making lith prints, the second stage could be done in daylight, plus the possibility of being able to make lith prints from 8x10 paper negs just seems like a really, really good thing : )

As always, any thoughts are welcome..

 

[removed account4]

i never really find paper negatives to be uber contrasty.
often times i process them in coffee developer which helps
often times i use expired ppaer which helps
and
often times i photograph on days where there isn't
excessive / drastic shadow and sun, so open shade or overcast light ..

 

[nmp]

You can't use a ferricyanide + bromide bleach, because it's a rehalogenating one. It means that it converts metallic silver back to the silver bromide form it came from. If you do use it, then you'll get a totally black image as a final photo.

I asked a similar question earlier on the thread, however that was about K ferricyanide by itself - not in conjunction with KBr, like it is used in Farmer's reducer. Later upon reading some more literature (particularly the EK patent I linked earlier,) my thinking is that K ferricyanide is just not strong enough an oxidizing agent to complete the bleaching. KBr will aid in pushing the reaction further (solubility constant of AgBr is orders of magnitude lower than Ag ferrocyanide.) But then you end up with something that will photo-reduce/darken in the second exposure/developer, as you pointed out. So that is a catch-22.

I wonder what would happen if you use potasssium citrate instead. If it helps with bleaching to achieve completion, the end product will be similar to peroxide/cirtic acid. This is also the basis for Cu toning chemistry, incidentally. With Ag citrate being sensitive only/mostly in the UV region, it would not participate appreciably in the reversal steps.

Unfortunately, I don't have the means to test out (debunk) these theories...so they stay as such.

:Niranjan.

 

[NedL]

I suspect there are different Ag citrate complexes with varying amounts of light sensitivity. At least some of them are sensitive all the way down into green and possibly yellow.

Silver acts as a catalyst for decomposition of H2O2 into water and O2. The reaction is interesting because it proceeds via two different pathways through unstable silver oxides. If you make a test strip of fully developed silver ( "max black" ) and wash it carefully, and put it into H2O2, it will sit there happily bubbling away and do nothing. The silver is being constantly oxidized and then reduced with no net change. If there are any impurities ( e.g. Cl ) it will lighten as silver salts are formed. Both citric acid and sodium citrate will "stabilize" the H2O2 and slow down the catalytic decomposition, and if you use sodium citrate it will "bleach" to white, but the result is quite light sensitive. I've also tried NaCl and KCl in 3% H2O2 and both will completely rehalogenate in a minute or two... so the original image will re-develop, even if the bleaching is done in the dark ( and can make a nice warmer tone image, so this could be of interest outside of reversal processing )

H2O2 mostly leaves the AgBr alone, I'm not sure that EDTA or other choices will do that ( or pot-ferri ) we need it to be left mostly unchanged so that it can be used in the re-exposure.... I found a century-old reference on using H2O2 for silver bromide papers and it mentions that the H2O2 does not leave the AgBr completely unchanged... it makes it susceptible to physical development. If you mix one of the rehalogenating combinations, I think you can observe this: in the light tones, you can see darkening... this doesn't happen in areas unexposed to light and it's not visible in areas with more developed silver... on my test strips there are always one or two steps where this happens. I suspect this accounts for the "reversal" that Don sees. Anyway... all my attempts to regulate the activity of this bleach by adding Na-citrate ( to make a constant pH buffer ) have failed... some of them "bleach" very quickly, in less than one minute... but those are the ones that form very light sensitive Ag Citrate complexes. ( BTW Ag citrates are soluble in citric acid, but very little at the concentrations we are using ).

I'm a few hundred test strips into this, and still don't understand it....
If you slow down the decomposition of H2O2 too much, by adding too much citric acid... the bleaching does not stop, but it does change... it relies on dissolved air ( I think likely O2, but not sure )... which becomes locally exhausted very quickly and then the bleaching proceeds only as fast as the air can dissolve into solution, and if not agitated, faster near the surface. If you take a test strip like this out and let it sit on you desk and dry, it will bleach very quickly as the air becomes available. I think this explains part of the reason Joe finds different kinds of agitation work better. Right now... my working hypothesis is that our citric acid - H2O2 bleach is usually in some middle ground, where it is a combination of the reactions driven by H2O2 decomposition and dissolved air. The final result of these two are different: the dissolved air one leaves a cream or light tan "white" and it is more sensitive to light..... ( BTW it's important to note that BOTH are light sensitive, just that the Ag compound produced w/ only weak CA is much less so... this is why everyone is finding the amount of re-exposure matters ).

I'm still holding off writing more about my tests because I haven't started the final part yet. I've only been looking at bleaching and then how fast the bleached area prints out in light ( I did re-develop a few that included a halogen just to prove they act as expected, including a few produced with Na-citrate as the "pseudo-halogen". ). I suspect that the two forms of CA bleaching will re-develop differently because trying to make real photographs I've seen some come out with light tan highlights and others come out with nearly neutral highlights. I haven't proved it yet but I suspect what we'll find is that unfortunately these go in the wrong direction from each other: I think if we keep CA concentrations low enough that the rx is mainly driven by H2O2 decomposition, we'll get low sensitivity whites that develop into a rather ugly light tan color... and if we increase the CA until it's mostly dissolved gas driving the reaction, we'll get much more light-sensitive whites that take on a light-neutral tone depending on the amount of re-exposure. The good news is that at the end, if there is tan in the highlights, it can be bleached back to bright white in very weak pot ferri reducer...

 

[DonF]

Great writeup, Ned. You have taken the analysis of this to another level entirely.

In light of others' postings this makes a great deal of sense, chemically and practically.

It makes me despair of getting a consistent result with the peroxide, however!

Best,

Don

 

[removed account4]

im an outlier and part of the fun of it is getting INconsistent results.
i've been partial bleaching going back and forth between CA and HOHO
and giving a quick ( or not so quick ) lights on
and into the developer until it starts to develop and then into the fix
getting beautiful colors and interesting partial reversals.
and since it isn't too bad toxic-wise i don't mind having it in my bag or tricks

 

[DonF]

I am inconsistent (as well) in my despair! Hmm, I have a jar of unopened sodium citrate on the shelf,,,,,

Don

 

[himself]

oh it's pretty inconsistent to be sure, and if I'm honest I don't really understand much of ned's great (and very detailed) write up., so I suppose it's lucky paper is relatively cheap : )

 

[DonF]

A box of 250 sheets of Arista EDU Ultra RC Black & White Photographic Paper, Glossy #2 5x7 just arrived!

 

[Anon Ymous]

Ok, I haven't read all the thread, just a small portion of it and (truth be told) I'm a tad too lazy to do it. What I'm wondering is why not a permanganate bleach?

 

[NedL]

Ok, I haven't read all the thread, just a small portion of it and (truth be told) I'm a tad too lazy to do it. What I'm wondering is why not a permanganate bleach?

Speaking only for myself:
1) (Main reason!) because I always have 3% H2O2 and citric acid here for other photo purposes, and it sounded fun!
2) because I was hoping for a fairly non-toxic and safe way to do it...and the permanganate formulas I've seen need sulfuric acid.

But you've got a point and someone pointed out that the sulfuric acid might be replaced by sodium metabisulfite, in which case it can probably be made pretty innocuous too.

 

[NedL]

It makes me despair of getting a consistent result with the peroxide, however!

I'm actually leaning the other way. I think it explains the very inconsistent results we are getting from each other, but I think if you use the process so that it leans mostly one way or the other ( low or high CA ) it should be possible to dial in the re-exposure to get consistent results. I think if you land in the middle, where you've got some of the "fast, low CA, driven by H2O2,non-actinic" bleaching and some of the "slower, high CA, driven by dissolved air, actinic" bleaching, then it's going to be hard to re-expose correctly. The difference in the needed re-exposure is around 2 stops, and the more of the bleaching that happens "hi CA" the more it matters.

I've had two periods of trying to make actual photos...at first I was using tiny amounts of CA ( 20% solution in an eyedropper...putting in only a few drops ), and the second adding more dry CA. Both times the results were pretty consistent as I was going along, but it was confusing because I was expecting things to act the same when it was almost two different processes.

BTW I think Joe's approach of going back and forth between weak CA and H2O2 makes great sense. When you first put the CA-soaked paper into the H2O2, the decomposition will be inhibited by the CA in the gelatin. Then as the CA leeches out and the H2O2 diffuses in, the decomposition will start and that will be the main kind of bleaching. Eventually you might get enough carryover to push it the other way, but not for a while. So I think this should be one "consistent" way to go at it. If you have some pot ferri and some hypo, do try that at the end... it's impressive how it can make the highlights pop out without messing up the darks. I've found about 0.3% pot ferri for 30 seconds followed by about 5% hypo works great. You can go back to the 0.3% pot ferri for another 30 seconds if it didn't go far enough. The light tan highlights left over when you tilt the process in this direction are particularly easy to remove this way.

 

[Anon Ymous]

...
2) because I was hoping for a fairly non-toxic and safe way to do it...and the permanganate formulas I've seen need sulfuric acid.

But you've got a point and someone pointed out that the sulfuric acid might be replaced by sodium metabisulfite, in which case it can probably be made pretty innocuous too.

You certainly don't have to use 98% sulfuric acid for a permanganate bleach, battery acid, or whatever dilute form will do just as well, but you have to adjust the quantity used. If it still feels unsafe, then using sodium bisulfate is another alternative. It certainly is easier do deal with, especially considering spills. The sodium metabisulfite you mentioned must be used as a clearing bath after bleaching.

 

[removed account4]

permanganate is crazy stuff too .. i bought some on ebay or the rain forest from a
guy who sells it to people to soak their feet in it . but i hear it is also used for other uses.
the permanganate _ bisulfATE / bisulfITE clearing bath recipe is on the unblinking eye website and can be tricky.
there was someone on the LF site who uses that process, others i have read about do it with limited success
and from what i remember they sometimes get weird streaking ... i was able to get one of them at a pool supply store
( now i seem to have a lifetime supply ) and it can be converted into the "other one" by using it with vinegar ...
seemed like too much effort for me ..

 

[DonF]

Potassium permanganate has a reputation for softening film emulsion when used as a bleach. I have no personal experience using it with paper, however.

I have used potassium dichromate/sulfuric acid with very good success as a paper reversal bleach. It hardens, rather than softens the emulsion, a good thing. I used common battery acid from the local Autozone ($8.00 USD for a quart of 35%), which can easily be diluted down to the required concentration for bleach preparation, either potassium permanganate or potassium dichromate. 35% is not too bad to handle. It requires eye and skin protection, of course. Once diluted to the strength in bleach, it is much safer to handle. The box I bought states specific gravity of the solution, but not percent concentration. There are tables that can easily be used to determine the percentage. In my case, the SG on the box was 1.265, which is about 35% at room temperature.

Potassium dichromate is nasty stuff when dry, but safer when in solution and diluted, as their is no danger of inhalation. It requires a somewhat different clearing bath to remove the orange stain after bleaching, sodium sulfite at 5% (normal hypo clear solution). The sodium sulfite can be used to make the orange bleach less toxic by adding it to the bleach. The orange color will turn to green. It is still toxic, but less so. The solution should be disposed of properly.

I use the following formula, scaled to the 35% sulfuric acid concentration from the Kodak published R-9 bleach formula:

Potassium Dichromate Bleach
===========================
700ml of distilled water
34ml 0f 35% sulfuric acid (1.265 SG battery acid concentration) - ADD ACID TO WATER!!
9.5g potassium dichromate
Add water to make 1000ml.

Regards,

Don

 

[himself]

I just wanted to share a quick update about an experiment I tried today.

I'm curious to know if it would be possible to produce a lith print from this process and today I had 5 minutes make a couple of test prints. As a quick preface, I'll say that the lith developer I'm using is what's left of a very old batch (that I was a little surprised still worked) and that I'm using some very expired Forte paper. I rated the paper at iso 1.5 like the ilford and used the same process except that I re-exposed in daylight assuming that like a normal lith print it would require more than normal.

And so the results, first of all the paper is much slower than 1.5, so not sure how useful it will be for this process. It seemed to bleach fine, and in the same amount of time as the other paper, it also developed in the lith developer for the final stage. However, it doesn't seem to have reversed, like at all. The negative bleached completely away, but after re-exposing the lith developer seems to have redeveloped the same parts of the paper creating a very nice, but negative print.

Is there something about the lith process that could do this? or is it something to do with either of the exposure stages?
The initial negative looked more normal than previous prints and not over-exposed, so could this be why?

 

[himself]

had another day making prints today, but had to make a new batch of bleach. Since then the images the highlights look spotty and have a very distinct gold cast. If I had to guess they look a little overexposed on the second exposure, but that would mean that each second exposure would need to be matched to each new batch of bleach, could that be the case?

as always the overall exposure, mid tones and shadows look fine.

 

[NedL]

If the H2O2 bleach is contaminated with any halogens, it will rehalogenate the original negative image and it will develop out again. I've done this intentionally by adding KCL, NaCL or Na-citrate ( with no CA in any of these ). It happened on my last one too, by mistake. I think some bromide got carried over from the 1st developer -- I was trying to shorten and simplify the process and it didn't work. It actually made these beautiful bronzed brown/coppery tones that were wonderful and shimmery, but it was mostly a negative image with some reversal around the edges.

If you have any potassium ferricyanide, try making a 0.3% solution and putting your print into it for 30 seconds. Follow this with a weak 5% sodium thiosulfate bath where the changes will become visible ( or any fixer should work too, if that's what you have, but you'll need to use it 1-shot and discard when done, or I guess you could save it just for this purpose... just don't use it as normal fixer again! ). You might find it will remove the gold cast, but not touch the darks much if at all.

Also, for anyone trying this, if you use replenished developer like I do, be careful about washing well before 2nd development. I don't think H2O2 would be good for any developer!

I don't do lith printing, but I suspect you could use H2O2 w/ a halogen and then do "2nd pass lith" on papers that otherwise don't lith well. This would be for a print not a negative.

 

[himself]

If the H2O2 bleach is contaminated with any halogens [...]

thanks Ned, that's really helpful. It was a completely new batch of bleach that I hadn't tried, so I'm wondering how it could have gotten contaminated, other than me maybe not washing the print enough after first development. Do you think I should throw away that batch of bleach then? I probably will just in case, but it's not like I don't like the gold cast, it's given them a really nice texture. It would be good to know why it's happened tho'.

unfortunately I don't have any potassium ferricyanide, so they will have to stay as they are for now.

a 2nd pass lith was my first thought, but I was hoping not to have to add another stage/variable.. now having said that, I have some prints that aren't usable as they are and so might as well be experimented on : )