Restrainer in Parodinal? KBr or BTA

Herzeleid · Jan 4, 2023

Hello everyone,

I was wondering if I could replace KBr in the parodinal formula with benzotriazole. If so should we replace it completely or partially? What would be different?
Parodinal formulation I am using now contains %1 KBr.

I have no experience formulating my developers, so I am curious if these compounds are even interchangeable.

Thanks

relistan · Jan 5, 2023

Herzeleid said:
Hello everyone,

I was wondering if I could replace KBr in the parodinal formula with benzotriazole. If so should we replace it completely or partially? What would be different?
Parodinal formulation I am using now contains %1 KBr.

I have no experience formulating my developers, so I am curious if these compounds are even interchangeable.

Thanks

I have not made parodinal but they are both restrainers. Benzotriazole is a stronger restrainer of fog without much impact on developer activity. Potassium bromide is a general restrainer, has an impact on fog and development activity, and can affect the solvency of the silver halide and thus the grain appearance. I would suggest they are not generally replaceable, but it depends on exactly what purpose the potassium bromide is serving in the formula. I would guess you are benefiting from some solvency and might get worse grain behavior with benzotriazole in place of the KBr. But if you are trying to deal with fog, adding some benzo to the working solution might be a good idea.

relistan · Jan 5, 2023

Here is a much better and more in depth explanation https://www.photrio.com/forum/threa...out-restrainers-for-film.188884/#post-2502447

Don_ih · Jan 5, 2023

I never put restrainer in Parodinal. Aceteminophen, sodium sulphite, and sodium hydroxide. Where did you get a recipe with potassium bromide in it?

Herzeleid · Jan 5, 2023

Don Heisz said:
I never put restrainer in Parodinal. Aceteminophen, sodium sulphite, and sodium hydroxide. Where did you get a recipe with potassium bromide in it?

I can't find the website with the formula at the moment but I will share the recipe I have used. I replace NaOH with KOH, it never forms crystals.

Parodinal-K
Potassium Hydroxide.......................28,3 gr
Paracetamol........... 15gr (Not tablets, from powdered paracetamol)
Sodium sulfite........ 50 gr
KBr........................2.5 gr
Water.....................250ml

Herzeleid · Jan 5, 2023

relistan said:
Here is a much better and more in depth explanation https://www.photrio.com/forum/threa...out-restrainers-for-film.188884/#post-2502447

Film fog is not an issue for me. I am just considering possibilities, I will read this post in detail again. Partially replacing Kbr does not look like a bad idea at the moment.

Thanks a lot

relistan · Jan 5, 2023

@Donald Qualls had a bunch of different formulas, some of which were "low fog variant" and had KBr. But I went and looked at his old site and they had nowhere near that much:

Developer formulae, dilutions, and times

Film developing information

web.archive.org

Don_ih · Jan 5, 2023

relistan said:
nowhere near that much

2.5 g seems like a massive amount - but not if used diluted 1:100 --- that ends up being .0001 g kbr per ml. Even at 1:25, it's .0004 g/ml. It's less than the amount of KBr in D72 at 1:3 (.0007 g/ml).

Herzeleid · Jan 5, 2023

Don Heisz said:
2.5 g seems like a massive amount - but not if used diluted 1:100 --- that ends up being .0001 g kbr per ml. Even at 1:25, it's .0004 g/ml. It's less than the amount of KBr in D72 at 1:3 (.0007 g/ml).

It is puzzling to me. I haven't observed any adverse effect of that amount. I usually expose for half the box speed of the film. I have also used this formula for developing my silver-gelatin dry plates. Base fog is there with the films and plate I have developed. It is not excessive but within acceptable levels.

relistan · Jan 5, 2023

Ah you are quoting a formula for 250ml and Donald's site is 100ml. That means you are in fact using the same amount he recommended. Sorry to have missed that.

Herzeleid · Jan 5, 2023

relistan said:
Ah you are quoting a formula for 250ml and Donald's site is 100ml. That means you are in fact using the same amount he recommended. Sorry to have missed that.

He has so many variations of the formula. I have just realized that. Some do not contain bromide.

Don_ih · Jan 5, 2023

I consider benzo a better fog restrainer than KBr, which I find lowers contrast. However, changing from one to the other will likely have an impact on development times. I'm not sure how it would behave in parodinal.

Herzeleid · Jan 5, 2023

Well, thanks a lot for your input. I have recently prepared parodinal with NaOH and it has crystals at the bottom which annoys me. I might dump it. Instead, I might add benzotriazole to it. Since the amount of KBr in the formula I have used seems very little in comparison to Donald's final low fog formulation and D72. %10 of KBr mass seems sensible. I come up with that number after observing ID62 formula which uses both restrainers.

Donald Qualls · Jan 5, 2023

I abandoned the low fog variants of Parodinal after finding little or no difference with any of the KBr levels I tried. I never tried benzotriazole in Parodinal -- as suggested, I'm pretty sure it would require longer development time (testing on ortho film, where you can easily develop by inspection, would be a starting point to get a differential time relative to no BZT).

And crystals on the bottom of either early-2000s commercial Rodinal or Parodinal are common and were considered normal when Rodinal still came from Agfa, they simply indicate something is in saturation in the solution (IIRC, the chemists suggested the crystals were probably either sulfite or the sulfonate of p-aminophenol).

Herzeleid · Jan 5, 2023

Donald Qualls said:
I abandoned the low fog variants of Parodinal after finding little or no difference with any of the KBr levels I tried. I never tried benzotriazole in Parodinal -- as suggested, I'm pretty sure it would require longer development time (testing on ortho film, where you can easily develop by inspection, would be a starting point to get a differential time relative to no BZT).

And crystals on the bottom of either early-2000s commercial Rodinal or Parodinal are common and were considered normal when Rodinal still came from Agfa, they simply indicate something is in saturation in the solution (IIRC, the chemists suggested the crystals were probably either sulfite or the sulfonate of p-aminophenol).

Thank you, Donald. I don't have enough film stock to do a comprehensive test about the effect of KBr amount. How little effect on the base fog are we talking about, do you have any numbers?

I had crystals with my Agfa Rodinal bottles, but compared to what I have with the recent batch, the amount in the original Rodinal solution was negligible. Using KOH instead of NaOH gives a cleaner stock solution, IMO. I am using the Parodinal K variant nearly more than 2 years. I do not see any shelf-life problems with it.

Donald Qualls · Jan 5, 2023

I didn't then have the instruments to measure base plus fog values (now I'd use my spotmeter with +10 diopter to get at least a comparison, but I didn't have diopters to fit the spotmeter at that time); I did eyeball comparison of 35mm .EDU Ultra 100 and 400 rolled from the same bulk rolls. All Parodinal variants I tried produced visibly more fog than HC-110, there was no or almost no visible difference between no KBr and the largest amount I tried.

Restrainer in Parodinal? KBr or BTA

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