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B&W Reversal: thiourea as fogging developer?

pkr1979 said:
@Raghu Kuvempunagar - do you adjust first developer time if using thiourea as a nucleating agent instead of as a fogging developer?
Click to expand...

I didn't have to but I've tried only on Kodak Double X and the previous generation Orwo UN54. You may need to adjust the acidity and duration of nucleating bath for your film. The less acidic the nucleating bath the warmer the positives as more silver sulphide specks are formed. Try first on non critical film with exactly the same steps as your tested process except for the light exposure which is now replaced by the nucleating bath.
 

Thanks! It is instead of a fogging developer though
 
pkr1979 said:
Thanks! It is instead of a fogging developer though
Click to expand...

Just as one would use a normal second developer after light exposure, here also one would do the same. Only light exposure is replaced by the nucleating bath. Hope this is clear
 
Today I tried using thiourea as a nucleating agent (if that is the correct term) prior to the second developer instead of as a fogging developer.

Meaning, instead of First Developer - Bleach - Clearing - Thiourea Fogging Developer,
I did First Developer - Bleach - Clearing - Thiourea Reversal Bath - Second Developer - Fix.

The parts that are the same I kept the same, meaning I exposed Ferrania Orto 50 at 32-40 ISO, First Developer was 14 minutes with 2.5g/L Thiocyanate. This produces good slides with thiourea as a fogging developer, but when replacing that with thiourea reversal bath, second developer and fix the slides are too thin and too low contrast (bright highlights but grey blacks). The tone is neutral.

I'll try this again by lowering First Developer time, amount of Thiocyanate, or increasing ISO. But before I do this - @Raghu Kuvempunagar - I did the thiourea reversal bath for 5 minutes instead of the 3 minutes you have suggested. Do you know if that might also be a factor in addition to First Developer times causing the positives to be to thin+low contrast? And, if I want slightly(!) warmer slides, can this be achieved by reducing the amount of acetic acid in the thiourea reversal bath?
 
You can reduce acetic acid to get more warmth. I think I mentioned this in one of my previous posts - "the less acidic the nucleating bath the warmer the positives as more silver sulphide specks are formed." By reducing the amount of acetic acid used, you can make the bath less acidic.

Before you do further changes to your process such as thiocyanate concentration in FD, FD development time, etc. you can perhaps do a simple test. Take a piece of unexposed film, put it in the nucleating bath for 2-3 minutes, develop and fix. Check the result. Ideally it will be very dense blocking most of the light when you hold it against a light source. OTOH if it is too thin, then no change in the earlier steps of reversal process can give you good blacks. Also, this test will give you an idea of the dark tones that are possible if you repeat the test with varying concentration of acetic acid.

Nucleating bath shouldn't be longer than necessary as there is the risk of losing some halides due to the formation of soluble Thiourea-silver halide complexes. I suggest keeping the nucleating bath to 2-3 minutes.
 

Will do - thanks.
 
Related work which discusses a nucleating bath made using 1000 ml of water, 5 ml of glacial acetic acid and 0.4 g of thiosinamine (allyl thiourea):


Quoting from the patent:

"Suitable odorless sulfur compounds for producing silver sulfide nuclei are, for example, thiourea and its derivatives"

"The process is suitable for the reversal development of any black-and-white or color picture"

"These acid baths have further the great advantage of a much Ionger duration than the hitherto known neutral or alkaline baths. The nature of the acid used is without importance; its pH-value being alone decisive."
 

Thanks for this.
 
Im not getting proper results when using thiourea as a nucleating agent and I am hoping for some advise. I lowered FD time from 14 to 10 minutes, and thiocyanate from 2.5 to 2 g/L. But results are similar:

Notice also that the top part is darker than the bottom part. Any advise?

@Raghu Kuvempunagar - how are you using/mixing dithionite for reversal? Im considering to mix something up myself instead of IronOut.
 
Not really sure if this going to solve any of the problems you're facing, but since you asked for my formula, here it is: 5 g Dithionite + 5 g Sodium Carbonate + 500 ml water. It should be used immediately after mixing, redevelop for about 10 minutes with sufficient agitation (initial 30 seconds continuous agitation followed by 2-3 inversions every minute thereafter).

@grainyvision who tinkered with Dithionite a lot more than me suggested another formula for fogging redeveloper: 1 tablespoon of ascorbic acid, 2 tablespoons of baking soda, and 2 tablespoons of iron out. I haven't tried this formula and not sure if it will solve your problems, but sharing with you for your reference.

The top-part darker than bottom-part issue is probably a processing error.
 

Thanks again for your help - much appreciated. Its probably not solving the issue regarding using thiourea as a nucleating agent. But Im not sure how much more I will be experimenting when IronOut and thiourea fogging developer works just fine. But Im curious to see if I can leave out fixing if I mix dithionite myself instead of using IronOut. IronOut does give good results though as long as I fix. The results are also good when using thiourea as a fogging developer. You are probably right about the top-part being darker then the bottom-part being a processing error - I just haven't experienced it before.
 
pkr1979 said:
Im curious to see if I can leave out fixing if I mix dithionite myself instead of using IronOut. IronOut does give good results though as long as I fix.
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If you saw the reddit link I shared in my previous post, @grainyvision seems to have got good result with Iron out without needing to fix. So I take claims that fixing is necessary to get clear highlights and good contrast with a little bit of scepticism.The issue that you are facing with IronOut might be due to inadequate development of highlights in the first developer. Have you tried developing a little longer than your standard development time and/or increasing the amount of thiocyanate in FD by a small amount?
 
  • Raghu Kuvempunagar
  • Deleted
  • Reason: Same post as the previous one.No idea how it got posted twice.

Thanks - yes, I saw the reddit link I have developer with longer FD time, more thiocyanate and both - but all of that is overkill. I'll try increasing agitation with Iron Out and see where that takes me - and maybe time as well. More like you do - Ive been agitating 4 times initially and 4 times half way (total time 6 minutes).
 

You might also want to try @grainyvision's redeveloper and see if it fares any better.
 
Hi!
Chiming in with a basic question: Are you guys doing all this processing at room temp? Especially the redevelopment in the thiourea mix.
Might as well try myself but still waiting on the thiourea to get shipped and wondering if I should get a sousvide or similar.
 

Room temp - just like negative black and white.
 

As someone that is interested in this process please do update us once you try. It seems to me that even if this process can’t give you maximum dmax it should result in positives that have their own look. Plus, they would probably be easier to scan than the super dense versions many people aim for.
 
Unfortunately, I was out of home during the holidays but I'm currently getting back to it. My first 2 test were terrible failures but I did do them in a rush before I left. However, for my formula I'm trying to use a peroxide based bleach instead of the classic permanganate/dichromate bleaches to make the process safer, but I'm not sure (or can't recall) if someone has used this 2 chems together for reversal, most peroxide bleach reversal are done re-exposing with light, so this might be my point of failure. Also note that this is my first time doing any type of developing, so I'm sure that doesn't help either.

one of my test strip failures, this was supposed to be a portrait.. .
 
I remember in the early 70's I ordered several Navy Surplus sepia toned reversal developing kits from a surplus company. I used them to process 8 and 16mm movie films and they worked very well. They were a standard high contrast developer, the normal dichromate sufuric acid bleach, clear, but then there was a sufide sepia toner with the common rotten egg smell that replaced second exposure and development. So the movies were sulfide sepia toned, which makes them look better in my opinion as well as much more permanent. Transparencies for projection are subject to much higher light levels than most photo materials, so the stability is an important factor. A sepia toner would be easy to mix and inexpensive, but probably should be used outdoors.
pkr1979 said:
Cheers
Peter
Click to expand...
 

Reversal processing as your first foray into developing? Brave! There’s more to go wrong with classic reversal processing so it’ll be harder to figure out what’s going wrong. If you keep posting your process and results you’re sure to get some help here.
 
FIRST SUCCESS... Sort of...
Managed to get this image

Incredibly contrasty and possibly overexposed?
Interesting tint, a little more aggressive than I would have liked, but I know thiourea is a sepia toner after all.

The formula:
At room temp (20c)
Dev Ilford RT2000 (1+4 Dilution) - 60s
Stop Bath (480ml Water + 20ml Vinegar) - 30s
Peroxide Bleach (500ml 18% + 4g Citric Acid) - 120s
Water Bath - 60s
Thiourea (16g Sodium Hydroxide, 2.5g Thiourea, 500ml Water) - 60s
Accidental second Bleach - 30s

Was working in total darkness as my paper fogged under safelight, so I mistakenly dunked it in bleach again in the end...
 

Whoops! I hadn’t read back on the thread. Didn‘t realize you are doing paper reversal. Which paper are you using? If it is MC you can try putting a yellow filter on the lens to help reduce contrast. What safelight are you using? I can’t think of any papers that should fog under OC or red light these days. I have been out of the loop for quite a while though.
 
I'm using pancromatic, rc, graded (not MG) ilford paper. For safelight I tried a red 620nm LED from amazon, and it worked with some Ilford MG paper, but for the panchro paper it didn't :/
Been doing a lot of tests, here are some of the results:


These images are inverted as they are mostly dev tests (inverted), but I read somewhere that I should aim for a completely black image with this dev, seems I need a stronger dev and longer dev time

For bleach, according to Jon Van Cleaves guide, I should aim for an almost white image, but haven't gotten there yet. However, I really didn't follow his guide exactly as I'm trying to do it in just one step. It seems the best ratio now is my Bleach A formula, might need additional time, also seems that temp has way less of an impact than with the dev


Now I'm realizing that this might not be the thread for these, will make another thread for this specific process soon.
 
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