Yeah, Alessandro, I'm with Ron on the clearing-bath not needing thiosulfate. If present you are effectively "fixing away" your positive image while you clear the bleach.
nother thing I might worry about is an interaction between the citric acid stop bath and the bleach. One thing you might want to try is to add some of your freshly-prepared permanganate bleach dropwise (carefully!) to some of your stop bath. I think you may find that the purple colour of the bleach is discharged (citric acid is being oxidized) in which case there is a danger that some of your bleach is being consumed by leftover droplets of stop bath in your tank. I can't remember if citric acid is oxidizable by KMnO4 in this way. I know oxalic acid is.
I think you'll have to goof around with EIs and dev times to get the correct density and scale in the slides. I rarely hit the correct EI the first time around.
Is Eukobrom a paper developer?
Here's a page containing an image that was made in my current "process" (I mostly follow the Ilford PDF on reversal processing, but make some changes to the first dev time, silver solvent concentration, and I use the thiourea "toning" method and a dichromate bleach). The original slide is deep-chocolate coloured, but I scanned it in grayscale. The rest of the roll is underexposed due to me mis-estimating the EI from an earlier test strip. This one worked out okay. Scans are not always the best way to tell, but the image is clearly usable, and the positives are no grainier than this film under normal development (it was FP4 Plus).
In the next hour I'll try another strip removing the hypo from the clearing, inserting a supplemental wash after the stop bath, lenghtening a little the first developer time (say 15 minutes for 100 asa), all the others steps being equal.
Originally Posted by Photo Engineer
I'll report asap.
More likely some 17th century alchemist's brew. Dan
Originally Posted by Donald Qualls
- I've lenghtened the first developer time from 12 to 15 minutes: positives too thin. Next time I'll try with 13,5 minutes. Tetenal Eukobrom is a paper developer, I use diluited 1+4, or double the strenght the paper calls for.
- I've transferred the hypo from the clearing to the first developer but I dunno how it has affected the image.
I've also diluited the sepia redeveloper 1+1 (so that 10g/l becomes effectivly 5g/l): I use 250ml for all solutions.
- Still no damage to the emulsion (at least with T-Max 100): I'm lucky enough to have solutions at ambient temperature that is exactly 20°C during this part of the year.
So I've reconsidered the permanganate bleach as a valid alternative to the dichromate one.
Next time I'll try as follows:
1) first developer 13,5 minutes + hypo (crystals - 1 teaspoon)
I'll report asap.
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I've developed a third strip of T-Max 100.
Now I've used 13.5 minutes for the first developer.
Unfortunately I've also used the full strenght sulfide redeveloper (10g/1l, I use 250ml) for 5 minutes (previously it was 3 minutes).
Now this is for Jordan: I can safely say that the emulsion damage you were experiencing with the permanganate-sulfide process is caused more by the sulfide than by the permanganate.
Reason being because on my last effort, I've noticed massive emulsion peeling but this time not because the permanganate (since I've not varied this step) but because of the strenght and the time of the sulfide redeveloper. So I think the sulfide is causing more damage than the permanganate does.
However, also decreasing the first developer time from 15 to 13,5 minutes didn't help at all, because I've obtained the same thin positive as per my update #2.
A question: is the hypo paramount at all?
The fact that I was using the hypo in the clearing bath is not mine: it's known from a reversal kit produced by the photochemical brand Chimifoto Ornano (developed by the chemist Oscar Ghedina), a very well known brand here in Italy.
I'm asking you this because once Dr.Wood said: "Forget the thiocyanate, you don't need it" and because I know the Foma Kit doesn't contain any silver solvent (because you can reuse the first developer solution as the second developer).
Plus I didn't notice any fog in the highlights when putting the hypo in the clearing bath.
After all, being a silver solvent, the hypo does the same thing whether is used in the first developer or in the clearing bath. I however noticed that using the hypo in the clearing bath doesn't make the emulsion "rough" at sight, whilst using it in the first developer makes the emulsion "rough"
Alessandro, the highly alkalline Na2S solution is probably detrimental to gelatin, due to the high pH and sulfide concentration. Did you measure the pH of the redeveloper?
For example, even thiourea is not recommended over a concentration of 3.8% at any pH as it will dissolve gelatin. Thiocyanates can have a similar effect at high concentration. Many compounds will damage the integrity of gelatin at the right concentration or pH or combination of these two.
Unless you want the brown images, then why use Na2S? Or, if you want the brown image, but object to the effects on gelatin or are having problems finding the right process conditions, then try a normal developer and then tone the final positive image in a separate toner, once you weed through all of the process effects.
From the sounds of it, you need to decrease development time in the first developer even more. Perhaps you should do a time of development series. It might even be that the exposures were off, but the development was correct. A check of the first developer and exposure can be made by just developing and fixing using a scene with a chart such as a MacBeth chart. All of the steps in the neutral scale should show in a perfect exposure/development combination. Any errors will show up in a deficit in the tone scale at one end or the other (poor dmin or poor dmax). And remember that this has to be qualified to account for the effects of the solvent developer.
I mainly use sodium sulfide because of its practicity: having a solution that does the redevelopment instead of the much more messy light re-exposure.
As I said, I've obtained perfect non-damaged emulsion just halving the concentration of the working sulfide redeveloper (going from 10g/liter to 5g/liter and using 250ml of that). Maybe it's still overconcentrated: maybe it's sufficient only 2g/liter (which turns to be 500mg/250ml) for one 36exp. roll.
What do you think?
What I've found is this:
1) using the hypo in the clearing bath - 12 minutes first developer ---> dark slides;
2) using the hypo in the first developer - 15 minutes first developer ---> thin slides;
3) using the hypo in the first developer - 13,5 minutes first developer ---> thin slides exactly as before;
Next I'll try:
1) using the hypo in the f.d. - 12 minutes (T-Max 100 @ 50);
2) using the hypo in the cl.b. - 12 minutes (T-Max 100 @ 50);
this just to see the difference, both redeveloped in sodium sulfide @ [500mg/250ml];
3) beginning to try the above 1) and 2) using a light reversal process.
I'll report next week.
The mixture of sodium dithionate (also called hydrosulfite) and sodium bisulfite obtainable on supermarket shelves as "Iron Out" will fog and develop unexposed film and give a black image. It is not a sulfiding agent. It has in fact been used as a developer, but not much because of its fogging. A tablespoon per tankfull should do. In this use, you're going to let it go to completion anyway.
In the CRC handbook sodium hydrosulfite is the first name given.
However I've noticed that using a sulfide concentration of 500mg/250ml (that is 0,2% w/v) is not causing any peeling off the emulsion.
But I must be careful because the gelatine swells very much (and the solution stinks).
Other than that I think the dichromate way is the best because it tans the gelatine: it behaves like a permanganate bleach with hardener added.
In the next few weeks I'm going to try it, using my university lab facility (vent hood ecc...) ;-)