Reversal print processing video..new approach

[NedL]

Sorry about that.. I shouldn't try to write here when I'm in a hurry...

I was guessing that the non-reversal you saw w/ lith developer was because something had built up in your H2O2 ( maybe carryover of developer or even tap water ). Didn't mean to imply it had anything to do w/ the gold cast in the highlights w/ your new batch.

Have fun!

 

[himself]

Sorry about that.. I shouldn't try to write here when I'm in a hurry...

I was guessing that the non-reversal you saw w/ lith developer was because something had built up in your H2O2 ( maybe carryover of developer or even tap water ). Didn't mean to imply it had anything to do w/ the gold cast in the highlights w/ your new batch.

Have fun!

Ah ok, I get what you mean now, but it did bleach completely, so I don't think that's why it didn't reverse (not that I have a better idea why not). I'm out of lith dev at the moment anyway, so until the postman comes I'll have to wait.

And in terms of the gold cast, I made a fresh batch of bleach today from a new bottle and the images are still coming out gold. It's not like it looks bad, so I don't mind, but it would be nice to know why.

 

[NedL]

Right! If there is any salt mixed in the H2O2, it will still bleach completely, and it will actually bleach much faster, but it will not reverse.
Re-developing will recover your original negative image.

For example, this test strip:

was exposed in steps under the enlarger, 0 on the right and close to max black on the left. It was developed and washed, and then bleached in H2O2 + salt ( no CA at all ) in the dark. After a couple minutes, it was completely white with no visible image at all. It was never re-exposed to light. Then when re-developed, we recover the same image, not reversed at all.

If this happened while you were trying to do a reversal, it would cause trouble!

 

[himself]

ok thanks, I'll keep an eye on that when I get chance to try again later this/next week.

so I've been thinking about the colour cast and my only thought is that I'm over-exposing on the second exposure again, but why it would have changed again I don't know. I noticed a similar colour cast to previous test strips, but that was only on the very edge of the prints. Either way I'll try reducing the second exposure to see how what happens.

 

[himself]

just a short update.

I made some new prints today and cut the second exposure down to 30 seconds and there appears to be no colour cast at all anymore.
I did also make up some new fix and gave all my trays a really good scrub, so I'm not sure which has made the difference, but reducing the second exposure (again) by half hasn't had any detrimental effect.

 

[NedL]

That's very interesting, thanks! What 2nd exposure were you using before?

 

[himself]

That's very interesting, thanks! What 2nd exposure were you using before?

I was using 4 minutes to begin with, but recently cut that down to 1 minute, but now I'm down to 30 seconds.
unfortunately there have been other variable changes during that time, so I can only really make an educated guess if that's had the effect of clearing the colour cast.
It hasn't made it worse tho' : )

 

[NedL]

Thanks... I've started experimenting a little with varying the re-exposure and it does fit. I've noticed that with what I'm calling "fast, low CA" bleaching, which is what I think most of you are using, it often happens that the most pure white at the end is a couple steps down from the most exposed part of the negative, then you see increasing amounts of color cast -- the final print has darker color cast in areas where you want it to be whiter. It makes sense that less re-exposure could reduce this and leave less color cast in the highlights at the end...( I haven't tried it yet, but it makes sense ) This would have implications for how to expose your paper negative.. you'd want to avoid blowing out the highlights completely or having details in the upper highlights, and try to keep detail in the middle range and shadows...

 

[himself]

that's an interesting theory, and I've been thinking about it also. Partly because I'd like in future to deliberately make prints with the colour cast.

the only thing I can add at the moment is that the gold cast seemed to be in the highlights even when there aren't any real "highlights", that is to say, I have a couple prints that are underexposed (due to sloppy metering), so the white wall behind the sitter is probably only really about middle grey. Could this then mean that it effects the lightest area (relatively speaking), rather than the true whitest?

I also have a print that shows a colour cast in what would almost be an area of pure white, but none in maybe zone VI/VII - areas which do have a colour cast in underexposed prints.

And I'm not sure if that even makes sense : )

 

[NedL]

It makes sense! ( Total guess coming next It could have to do with the length of bleaching....

I just finished processing one... the photograph isn't good but the processing went well and looks good...good blacks and whites and mids. Got one more to try later this afternoon. It's fun!

 

[himself]

but length of bleaching in what sense? my bleaching time is pretty consistent with all exposures - usually to completely white around 3 minutes.
I have noticed tho that with the longer second exposure more of the image comes back before redeveloping, so maybe it has something to do with that.

how did the others turn out?

 

[NedL]

This is what I was thinking: imagine you have one negative overexposed and one normally exposed... it could take the two negatives a different amount of time in bleach to reach completely white. A "zone VIII" area in one might have the same amount of "whatever makes the gold cast" as a zone "IX" on the other. But I agree if you are using about 3 minutes for all negatives, this explanation is probably too simple.

I had a disappointment. The second one I tried yesterday, the picture was really great. I left it face up in the bleach and at one point I got distracted and it sat for 15 minutes before I agitated it.. looked completely white after 30 minutes, I let it go 45m to be sure... but it has a big stain right down the middle. It must have bowed so that the center was near the surface of the bleach during that 15 minutes. I'm thinking of going back to try to recreate this one... but of course conditions will never be exactly the same again.

 

[himself]

that could make sense and of course there is the possibility that completely bleached to the eye is not completely bleached in fact.
it's probably just one of those things that's a combination of all factors, but at the moment my biggest (known) variable is the length of second exposure, which should be easy enough to test with a test strip made on the same print, that's just been bleached. I'll give it a go when I have time to make a test image.

That's a shame, and I guess is the big challenge when making such one off images. The image of the bath tub I posted earlier in the thread took me about 5 trips with mu 8x10 to finally get right : )

 

[NedL]

Exactly what I was getting at: completely bleached to the eye might not be bleached the same each time in fact. I think I'm at a similar point as you are... I've "locked in" the first parts of the process and am now trying to find the best re-exposure.

With pinhole paper negatives, I'm used to the "one off" chance... but this adds another step where things can go wrong! I'm hoping once it's dialed in a little better, it will be back to "is it a good photograph and was it exposed okay?"

 

[removed account4]

for what its worth, i've exposed and re developed things that werne't bleached white
the prints weren't happy ...

 

[himself]

I've done some that weren't so bleached, but they tended to end up with no shadow detail and very dark midtones, almost like the midtones didn't bleach (they seem to bleach later than the highlights) and just got darker with redeveloping.. but the highlights were ok.

it's starting to look like each step influences the others so much that there won't be a "standard", which is fine, it adds to the final image and whether it's a good/bad image I'm discovering : )

 

[NedL]

Yes, that fits what I've seen. If you use low to "moderate" amounts of CA, the bleaching is driven by the amount of silver on the negative, and the highlights bleach first, then the midtones and finally the shadows. The other day I was watching the darkest parts of the negative bleach almost to white before the next "zone" started, and thinking I should take some photos of it.. it's pretty cool! I've never tried to take a digi-snap under my safelight... not sure how it would work. If you use more CA, it goes the other way, with the lighter areas on the negative bleaching first, and lots of other characteristics change too ( e.g. the bleached areas are much more light sensitive, and it takes a lot longer to finish ).

I don't think there will be a standard. I'm trying to "standardize" on a bleach that takes about 1/2 hour, you and Joe are using higher % H2O2 and bleaching faster. I won't have the color cast, but mine might be more sensitive to the amount of re-exposure. I do think each step influences the others, so a practical approach is to pick something that works, keep the first steps the same, then find the right re-exposure for it.

Also, I still want to try using a lime and I'm planning to try EDTA just to see what happens, but that's separate now from dialing in a consistent repeatable process!

 

[himself]

If you use more CA, it goes the other way, with the lighter areas on the negative bleaching first, and lots of other characteristics change too ( e.g. the bleached areas are much more light sensitive, and it takes a lot longer to finish

an interesting point, so would it then follow that images bleached in fresher bleach will be more sensitive to light (after bleaching) than in older bleach?

that's kinda what I meant, so sorry if it wasn't clear. I don't think there is a way to standardise it even for a specific set of parameters (unless I suppose you were able to completely control everything). Each time I think I have a workable process some new thing crops up. It's like it always needs fine tuning.

*between writing that above and posting it I made another print

The new print (with the same process as the last three that came out great) is awful. It has a slight colour cast and what looks like road-rash. The only difference I can think of is that I didn't agitate as much as usual, and that the bleach has started to effect the gelatin/paper in places. This I think makes a stronger case for how active the bleach is causing colour casts and other artefacts.. how tho', I have no idea.

**update**

I've done a couple of prints since this post with the same batch of chemicals, but was much more careful about agitating the bleach, and they've both come out great with no colour cast or "rash". So it looks like if the image bleaches too aggressively, either because of poor agitation or because it's too strong, it will cause discolouring in the highlights and other defects to the final positive image - no matter how long the second exposure is.

I guess that seems fairly obvious, but it's good to have had it confirmed.

 

[NedL]

Not obvious... a lot of things about this don't go in simple directions. But one reason I'm trying to dial in a slower 1/2 hour approach is that I get fewer blisters and less color cast, and also it just seems more repeatable. I do think you can get good results either way, but it's best to pick one and figure out the quirks.

As for whether fresher bleach will make it more light sensitive, I don't know. It's logical that if the bleaching uses up some of the CA it might do that, but then the H2O2 will be decomposing too, so who knows? I've been using 3% H2O2 only as a 1-shot and then discarding it each time. I'm almost out of hydrogen peroxide again... so I've gone through 8 bottles since we started ( only 89 cents each, so no big deal )!

Definitely fun to see the positive come up at the end!

 

[DonF]

I've never tried to take a digi-snap under my safelight... not sure how it would work.

If you have an Iphone, Apple added a "Night Shift" feature a few releases back that changes the color temperature of the screen to a very warm reddish color at night (optionally). I turn this on manually (In Settings-Display & Brightness-Night Shift) and set to the warmest setting possible. I then reduce the screen brightness manually until it is just bright enough to act as a viewfinder. It works quite well as a "safe" display in that mode, when used with graded paper.

Best,

Don

 

[DonF]

for what its worth, i've exposed and re developed things that werne't bleached white
the prints weren't happy ...

I've done the same! They generally come out OK if the exposure was good and first development was to completion. HOWEVER - the image turns positive the first few seconds in the bleach and the POSITIVE fades slowly over the next few minutes. Incomplete bleaching seems less important if the image has somehow quickly reversed to positive in the bleach before the second exposure and development.

I have no idea why the image turns a visible positive in the bleach.

I believe the faint positive that is sometimes seen in a completely bleached image during the fogging (second) exposure is due to the action of developing agents that are included in some RC papers to speed development.

Don

 

[DonF]

Just thinking about this second exposure thing.

Most of the threads discussing "conventional" film reversal processing imply that the secondary exposure length is not that critical, as long as one does not try to use the sun or other UV-rich source and that all areas of the film, front and back, receive sufficient exposure. Apparently, extreme amounts of secondary exposure can push the unbleached areas into the solarisation region, which will produce a reversal of areas of extreme overexposure (black sun in landscapes for example). This is different from the Sabatier effect, caused by moderate light exposure while development is taking place, which can cause a partial reversal of the entire image.

It seems to me that the initial exposure is going to result in regions with varying levels of exposed silver halide, depending upon the density of that part of the scene. If the first development is to completion, virtually all of the exposed silver grains will be reduced to metallic silver. Only those grains will be (or should be) bleached by whatever chemical is being used. What remains are grains of unexposed silver halide.

My reasoning is that the overall density of the image is set by the initial exposure and development. One cannot over-bleach an image (ignoring other issues like emulsion softening, blistering, etc.) as the areas that can be bleached have already been determined by the first exposure and development. Likewise, one can not over-expose during the second exposure (nor over-develop during the second development), as it is desirable that all grains of newly-exposed and unbleached silver halide be converted to black.
In my thought model, each grain or crystal of silver halide has a binary state, black or not black, no in-between. Gray variations are caused by the density of the black particles in a region, rather than variations in the light absorption of the individual grains. I think this is correct, please feel free to jump in.

If the hydrogen peroxide bleaching leaves behind insoluble secondary actinic or light-sensitive compounds as part of the process, all bets are off and the newly formed light-sensitive compounds not related to the original exposure could cause all sorts of image defects, like the coppery stains we are seeing. It has already been stated here by those in-the-know that silver citrate, the product of the peroxide bleach with citric acid, it relatively insoluble and remains in the paper until fixing. It is also slightly light sensitive and may react with second exposure and development.

The silver citrate produced by the peroxide/citric acid bleaching is soluble at 28.4 milligrams/liter in water. The silver sulfate produced by the sulfuric acid in the dichromate bleach is soluble at 8300 mg/liter in water. It sounds like more of the silver citrate is remaining in the paper after/during bleaching, which may account for image issues during the second exposure and development.

Don

 

[NedL]

That's pretty much the way I see it too. I think there might be different kinds of silver citrate complexes that have varying light sensitivity. They are soluble in CA, and I worried about that because silver citrates are supposed to be powerful bactericides ( and I'm on a septic system ), but the solubility is very low at the concentrations of CA we are using.

Like everything else, whether this is good or bad is a matter of perspective. Assume for a second that we're completely right about H2O2. Then it's not a simple "there's silver or not" and "there's silver halide or not". It's more complicated to think about. But then again, it also means that you have some additional control over the results with the second exposure, that's not available in the simpler dichromate system. For example, we can use VC filters to alter the contrast in the final print... something that doesn't make sense if the goal is to "develop all remaining silver halides to completion". It might have more ways to go wrong but also more "creative control" as well.

 

[DonF]

If there are other light-sensitive compounds being formed in areas that should be bleached and light insensitive, I don't see how that could do anything but degrade the highlights, a problem that we are seeing routinely with peroxide (see the other dichromate thread)! One might have control over the density of the final positive by controlling the secondary exposure of the unexposed and unbleached, though. Controlling by second development time would be a bad idea, I think.

Don

 

[DonF]

Thinking about this a bit more, I don't think you would be able to control anything but contrast by adjusting the second exposure. The areas that are capable of becoming dark in the final print are those areas remaining after bleaching. If the image is too light because of over-exposure in the camera, no amount of secondary exposure can darken the areas that have been bleached away. You could increase the darkness (contrast) of what is left, though, but the image will still be too light.

Like this overexposure. If I increased the secondary exposure, the dark areas would get darker, but I wouldn't recover any detail.

Don