precipitation B&W reversal processing

mug · Aug 12, 2021

Last week developed 4 b&w films (∆100) in the reversal method.
I am using Ilford's workflow. And am working on optimizing the process. Which ISO, which developing time etc.
During the 2nd development bath I got a precipitation on the plastic parts of my development tank.
I am not satisfied with that. Something tells me that something in the process is not optimal when you get a deposit. In normal b&w development I have never had that.
Anyone have any idea where that precipitate from the 2nd development bath is coming from ?

Raghu Kuvempunagar · Aug 12, 2021

Permanganate bleach in Ilford's process can sometimes peel bits of emulsion from the film and these bits could be the 'precipitate' you observed. Have you checked the film after the second development? Does it show any damage to the emulsion? Do you have a picture that shows the precipitate or the film after second development?

mug · Aug 13, 2021

Thank you for your quick reply.
The emulsion adhesion is not optimal. At the place where I grabbed the film with my hand you can see damage.
See photo

In the light areas see that there are white spots.
See photo

I used 0,2% Potassium permanganate solution which I acidified with 14 mL 37% sulfuric acid (which is a very small excess)

Possibly too long in the bleach bath? Should have done 5 minutes at 20 ºC. But I did 5 min at 24 ºC. It was warm in my lab and for the developer I adjusted the time to 24 ºC but not for the other chemistry steps.

Raghu Kuvempunagar · Aug 13, 2021

Sadly, emulsion softening and subsequent peeling is a common problem with Permanganate bleach. Reducing the strength of the bleach can help in this regard - try 1% solution. Also, tight temperature control (20C) during the bleaching stage and the subsequent stages is advised. I use Dichromate bleach and it works perfectly. Copper Sulphate bleach also works fine.

BTW the second slide is gorgeous and it's a pity that the emulsion got damaged. Hope you can fix the problem in the next try.

mug · Aug 13, 2021

Thank for reply. Dichromate bleach I can make, but health friendly it is not. It is not environmentally friendly. May not be available in the future
That's why I don't choose it. Prefer a long term solution. Copper Sulphate bleach is on my list to test. But I found CuSO4 anhydrous expensive (€85,- kg) .
But the For CuSO4 5hydrate version at home. So I can try if I re-calculate the amounts.
Permanganate I need only small amount and it's cheap (I payed €5,- 100 gram) . Found document from a Agfa patent that add sodium potassium hexametaphosphate. That seems interesting!
Also read that an increasing the clear time can help for white spots. But found only 1x that idea, never a never a confirmation.
I happy with the density and contrast I found. Not with the white spots seen in the clouds. This stereo positive is made yesterday with a camera over 100 years old.

Raghu Kuvempunagar · Aug 13, 2021

Convenience offered by Permanganate bleach for the home user can't be questioned. I think if you use a weaker bleach with tight temperature control, you should be fine. No need to switch to a different bleach.

Sodium Hexametaphosphate supposedly increases the life of Permanganate bleach if you prefer not to mix the bleach from crystals every time.

Metabisulphite clear removes residual Permanganate in the bleached film and prevents the formation of stains. I don't know if it can help in preventing emulsion peeling.

Looks like you're all set to make great slides. Enjoy!

YoIaMoNwater · Aug 13, 2021

mug said:
Thank you for your quick reply.
The emulsion adhesion is not optimal. At the place where I grabbed the film with my hand you can see damage.
See photo

In the light areas see that there are white spots.
See photo

I used 0,2% Potassium permanganate solution which I acidified with 14 mL 37% sulfuric acid (which is a very small excess)

Possibly too long in the bleach bath? Should have done 5 minutes at 20 ºC. But I did 5 min at 24 ºC. It was warm in my lab and for the developer I adjusted the time to 24 ºC but not for the other chemistry steps.

What was the final concentration of sulphuric acid? I’ve used 0.12% w/v potassium permanganate in 2% v/v sulphuric acid at 20-22C and worked fine for lots of 35mm films. Raghu is right about the temperature as that can increase emulsion damage.

mug · Aug 13, 2021

I find it difficult to calculate in % for sulfuric acid . In chemistry, calculate in Mole is easier. I hope my conversion is correct
I make 550 mL of solution with 1.1 grams of potassium permanganate and 7 mL of 37% sulfuric acid.
I think that is equivalent 0.2% potassium permanganate in 0.32% sulfuric acid. This at 5 minutes at 24 ºC. Add the acid 5 min before I start and filtered just before start.
If I compare it to your percentages. So I have clearly more concentrated permanganate at lower acidity.
Next time I am going to bring the solutions to 20.0 degrees and choose the permanganate concentration lower. And then see if it gets better

YoIaMoNwater · Aug 13, 2021

You don’t have to convert them in moles since everything is done either by weight per volume (w/v) or volume per volume (v/v). The former is calculated by g/mL while the latter is mL/mL.

Since you used 7 mL of 37% sulphuric acid in a total volume of 550 mL, then your final sulphuric acid concentration is: 7 mL(37%) / 550 mL = 0.47%. I’ve read that the amount of permanganate is more of an factor than the amount of acid, although I have not tested this. But it makes sense because the permanganate just needs to be in an acid environment.

One thing you can do is to make a stock solution with 1.1 g of potassium permanganate (I assume you don’t have an laboratory analytical scale to get less than 1 g) in X mL amount of water, then take half of that for your final solution of 550 mL with the acid, so you get a 0.1% w/v potassium permanganate. Note that I would not store stock solutions of permanganate because it oxidizes into a solid black chunk of manganese oxide in days.

Also, are you using distilled water for the bleach?

mug · Aug 13, 2021

No I don't use distilled water, but no problem to do it.
Preserved bleach bath of 1 day old tested today.
Put through the filter ('k-cup reusable replacement coffee filter')
Already seeing brownstone.

YoIaMoNwater · Aug 13, 2021

The bleach should be the only step where you need distilled water, this is to ensure there are no chloride that can cause solarisation. Check out Table 1 here: https://unblinkingeye.com/Articles/PBR/pbr.html

The white holes in your slides are definitely from emulsion damage, which Jens Oshbar talks more about in his protocol (check out section 9.5.2): http://www.ars-imago.com/productinfos/osbahr_reversal_films.pdf

He observed that prolonged bleach causes holes in the emulsion, which seems like what has happened to you.

The precipitates you saw are manganese oxides and permanganate bleach are one shot only. The best way for long term storage is to actually keep the potassium permanganate solids in its container and keep it away from heat and moisture. Use only when you need to do reversal experiments.

mug · Aug 13, 2021

Thanks again a great help.
The artikel from Harvey W. Yurow Ph.D. is very, very interesting. Thanks!
The artikel from Jens Osbahr I already found myself. But not read good enough.
Did a check by my water company, indeed my tapwater contains 50 mg/L Chloride. So I going to use distilled water for the bleach solution is a good idea.
I think I'am going to do a test similar to the fix test to determine the best bleach time.

YoIaMoNwater · Aug 13, 2021

Best way to do this with every type of film is to cut a piece of the film leader and develop it in parallel with your roll. After first development, also bleach in parallel and occasionally check the film leader to see when it clears. That’ll give you a good idea of your bleaching time.

Raghu Kuvempunagar · Aug 13, 2021

I don't know if you do this. It might help to filter the bleach after mixing it as any residue in the bleach is likely to cause emulsion damage in the bleaching step. The color of the solution makes it difficult to see the residue.

Anon Ymous · Aug 14, 2021

mug said:
No I don't use distilled water, but no problem to do it.
Preserved bleach bath of 1 day old tested today.
Put through the filter ('k-cup reusable replacement coffee filter')
Already seeing brownstone.

Even if you use distilled water, you'll get brownstone after the first use. It's rather easy to spot, the deep purple solution becomes reddish and a bit dirty, at least this was my experience when doing it. If you use 20g/l sodium hexametaphosphate, then it will greatly prolong the solution's life, but eventually it will also form brownstone just by sitting on the shelf and lose potency.

Raghu Kuvempunagar said:
I don't know if you do this. It might help to filter the bleach after mixing it as any residue in the bleach is likely to cause emulsion damage in the bleaching step. The color of the solution makes it difficult to see the residue.

Yes, this is a good idea, and this happened to me at my first try, but the result was much different from the one in the initial post.

Raghu Kuvempunagar · Aug 15, 2021

Anon Ymous said:
If you use 20g/l sodium hexametaphosphate, then it will greatly prolong the solution's life, but eventually it will also form brownstone just by sitting on the shelf and lose potency.

When using Sodium Hexametaphosphate in Permanganate bleach, it might be a good idea to filter the bleach once in a while to extend its shelf life. Apparently, Manganese Dioxide, which is the brown precipitate formed when Potassium Permanganate reacts with water, acts as a catalyst for the reaction.

Anon Ymous · Aug 15, 2021

Raghu Kuvempunagar said:
When using Sodium Hexametaphosphate in Permanganate bleach, it might be a good idea to filter the bleach once in a while to extend its shelf life. Apparently, Manganese Dioxide, which is the brown precipitate formed when Potassium Permanganate reacts with water, acts as a catalyst for the reaction.

Hmmm, interesting information, thanks. The "solution should be protected from daylight" is also an interesting bit...

mug · Aug 15, 2021

The advice to run exposed film strip separately. was great. And to check the bleach time in daylight was a valuable tip.
My bleaching times have been drastically reduced. And the clearing times as well.
The result is fine. No more deposits in the development tank. No white spots in the light parts of the positive. Less soft emulsion.
My bleach bath is now 0.15% permanganate and 14 mL 37% Sulfuric Acid per liter at 23.5 ºC and 2.5 minutes.

I thought I already had nice results. But these results are much better.
The shorter bleaching time does affect the Dmax and contrast.
In the positives, the black areas are a bit too saturated. So I still have made slight adjust the ISO and/or development time.

Two sample pictures

Raghu Kuvempunagar · Aug 15, 2021

Is this Delta 100? How much Thiosulphate are you using in the first developer?

mug · Aug 15, 2021

Yes ∆100. (120 rolfilm). I use 3 gram Thiosulphate 550 mL 1:1 Bromophen as first developer.
What do you use ? What would you suggest ?

.

Raghu Kuvempunagar · Aug 15, 2021

I used ID-62 with appropriate amount of Potassium Thiocyanate earlier and then my own brew of first developer. Haven't reversed Delta yet, but your results are encouraging me to try.

precipitation B&W reversal processing

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