Stannous chloride and glacial acetic acid

pkr1979

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Hi all,

I've been mixing up 1g stannous chloride with 5ml acetic acid and then watering up to 500ml water (room temp) so the solution is 1% (since 5ml is very little some water has been necessary to cover the stannous chloride to mix it). Ive done this the night before developing black and white reversal (instead of light re-exposure), and this has worked very well. To be honest, Im not sure if its the amount of stannous chloride or the 1% acidic solution that makes it keep over night... beeing used the following day maybe stannous chloride and plain water would do despite hydrolysis.

Anyway, I tought Id mix up a 2L solution and check after some time if it would keep. Yesterday I mixed up 4g of stannous chloride in 20ml glacial acetic acid watering up to 2L (room temp). However, today already, hydrolysis is taking place... the solution is definitely not clear and I suspect it might not work. Ive mixed up stannous chloride with HCl and it holds, but Im not using that in a photographic process.

So, what Im wondering is if anyone has experience in mixing up stannous chloride solutions as a chemical re-exposure bath? Especially one that keeps? Im interested in all forms and experiences really.

Cheers
Peter
 
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pkr1979

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Hey man. I dont mix it with the developer. I run the stannous chloride solution as its own bath. Regarding the keeping qualities... Im not so sure I'll get anywhere with that... Ive been reading some gold digger forums and they make stannous chloride solutions with HCl to check for gold, and those solutions have good shelf life. It would be convenient to find a way to make a stable lasting stannous chloride solution that would have some proper keeping qualities. I'll test the batch I made in about six months just to see if it works, even though hydrolysis has occurred... maybe it hasn't occurred to all the stannous chloride. The only way I know to test it though is to actually develop...

Anyway, I suspect it will not work in which case I'll continue to mix up the evening before I develop. I find it to still be more convenient than re-exposure with light.
 

relistan

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Ah, interesting, yeah I see you are using it by itself. Definitely interested in how it keeps, please do report back.
 

Raghu Kuvempunagar

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HCl is one of the products of hydrolysis of stannous chloride. When you use HCl to make stannous chloride solutions, you're essentially forcing the equilibrium to shift left and thereby preserve stannous chloride. Another approach for increasing the stability of stannous chloride solutions could be what is suggested here and here.
 
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pkr1979

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Ive added Tin already. There is still abit of room for oxygen in the glass bottle though. Maybe Tetenal Protectan can help.
 
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pkr1979

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Its possible to mix at time of use, even the day before with acetic acid. Im just curious if its possible to make a solution that keeps. As for HCl I did that and it didnt work for developing film... I did it only once though as I started out BW reversal so some other factor MAY have caused the failure. It might be adjusted with HCl as well... but Im hesitant due to my experience and am curious if its possible with acetic acid instead (as I know this will not ruin your film and actually works).
 

YoIaMoNwater

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I didn't have too good experience with stannous chloride, probably because it was more than 4 decades old or it was from insufficient bleaching. I think @Rudeofus is more experienced with it and can provide some answers.
 

Raghu Kuvempunagar

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pkr1979 said:
Its possible to mix at time of use, even the day before with acetic acid. Im just curious if its possible to make a solution that keeps.
Click to expand...

Keeping the temperature of the solution low might reduce the rate of hydrolysis and extend the life of the solution.
 

Rudeofus

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Stannous Chloride based reexposure bathes suffer from sudden death syndrome, so don't rely on year long shelf life. Obviously Stannous ion is a strong reducer and will happily react with aerial Oxygen. Even tiny traces of Stannous ion will render silver halide developable. Your reexposure bath decays and decays with no visible effect on the final images, until one day the very last trace of Stannous ions becomes oxidized and the bath switches from functional to non-functional. Without a working reexposure bath you'll get blank slides!

There are two things you can do to improve shelf life:
  1. Make a concentrate to mix working solution as needed. Keep concentrate in glass bottle.
  2. Use a powerful sequestering agent like ATMP to prevent other trace metals from interfering
Here is a formula based on Kodak's patent for its 5l E6 kit. According to PE these recipes are "the real thing":

deionized water 25ml
Acetic Acid 80% 7.88g
NaOH 50% w/w 6.00g
Dequest 2006 12.83g
SnCl2 * 2H2O 1.98g
p-Aminophenol 0.6mg (yes, mg! )
deionized water ----> 50ml​

These 50ml reexposure bath concentrate make 2000ml working solution. In the patent the working solution is used single shot, but in my experience it will work throughout a whole evening with a half dozen runs. Don't overstretch it (c.f. sudden death syndrome). Note, that even liquids like Dequest 2006 and NaOH 50% w/w are given in grams, since weight can be measured much more accurately than volume.
 
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pkr1979

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The best thing one could do for a chemical re-exposure bath with some shelf life is probably to use that recipe... however... I discarded the batch I just made to try with colder water. What I wasnt aware of though is that the freezing point of acetic acid is 16C so it turned into a slush making it a pain to measure. Anyway, I also sprayed in some Protectan. The solution isnt as clear as I want it to be but there is less precipitation then on the previous batch. What I did though that I probably shouldnt have is that I mixed working solutions... Im thinking a better idea is to make a concentrate as suggested by Rudeofus. 5g in 250ml 100 acetic acid... Ill get a smaller bottle and give that a go.

EDIT: I would assume the stannous chloride would last a long time in a 100 % solution... but obviously I dont know this.
 
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Rudeofus

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Nobody can reliably tell you, how long these concentrates will last. PC-TEA allegedly lasts forever, but CD-4 in TEA turns deep purple within months. Watch out for sudden death syndrome! I wonder, whether a somewhat quantitative test with permanganate would work ...
 
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pkr1979

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Rudeofus said:
Watch out for sudden death syndrome! I wonder, whether a somewhat quantitative test with permanganate would work ...
Click to expand...

I will How would a quantitative test with permanganate work? I got the stuff and can try this out.
 

Raghu Kuvempunagar

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pkr1979 said:
The best thing one could do for a chemical re-exposure bath with some shelf life is probably to use that recipe..
Click to expand...

Rudeofus said:
Stannous Chloride based reexposure bathes suffer from sudden death syndrome, so don't rely on year long shelf life.
Click to expand...

Stannous chloride is perhaps indispensable to color reversal and one has to live with the risk of its sudden death. But I don't see any point in using stannous chloride in B&W reversal especially when there are more reliable and long lasting alternatives. One such nucleating agent that can be used in B&W reversal is thiourea. I've found that a three minutes bath in dilute (0.05%) thiourea solution acidified with about 40ml of glacial acetic acid does the trick. This bath has to be given to the film after the bleach and clear steps. It needs to be followed by two short rinses in water and ~10 minutes developing in a second developer. All steps must be done in total darkness.

The thiourea nucleating bath results in the formation of thiourea silver halide complexes. Some of the thus formed thiourea silver halide complexes decompose into silver sulfide specks in the alkaline environment of the second developer. These sulfide specks act as development centers for the remaining thiourea silver halide complexes which are then fully developed by the second developer. As bromide in the second developer inhibits the formation of sulfide specks, it is desirable that the second developer be one that has low bromide concentration. The positive image formed after the second development might have a warm tone due to the fact that development initiating specks are silver sulfide. However, the warmth of the tone depends on the film, composition of the nucleating bath and the second developer. I get neutral tone with Orwo Un54 when I use the nucleating bath of the composition I gave earlier and HC-110 as the second developer.

Rudeofus said:
Nobody can reliably tell you, how long these concentrates will last. .
Click to expand...

Thiourea lasts long as aqueous solution. A 5% solution can be prepared and 5-10ml of it can be used to prepare the nucleating bath. Like stannous chloride, thiourea is toxic and a suspected carcinogenic. Appropriate care needs to be taken while handling it.

BTW thiourea is not only a nucleating agent (in acidic solution) that can be used in conjunction with a regular B&W developer but also a powerful fogging redeveloper by itself (in alkaline solution), one that gives sepia toned positives.
 
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pkr1979

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Raghu Kuvempunagar said:
But I don't see any point in using stannous chloride in B&W reversal especially when there are better more reliable and long lasting alternatives. One such nucleating agent that can be used in B&W reversal is thiourea.
Click to expand...

Im using stannous chloride now mainly because its what I got. Figuring out if it has any keeping properties in acetic acid is more out of curiosity then necessity. When I run out I might see if I can get thiourea to try it out. Warm tones are fine, but I prefer straight black and white over sepia though.
 

Rudeofus

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There is absolutely no reason to perform reexposure bath or second development in darkness. In fact the main beauty of a reexposure bath is, that one does not have to put light on the film, but it certainly won't hurt after first developer has been washed out.

I don't know, what the reason was for not choosing Thiourea as fogging agent, but it was never used for this AFAIK. Either even dilute bathes "develop" too much silver halide, or there is some limit of shelf life we do not know yet. Photographic industry certainly would not have used this nasty boron compound, if Thiourea could have been made to work.
 

Raghu Kuvempunagar

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If you're going to do second development with lights on or in day light, you might as well skip the nucleating bath and go for light exposure.


If you're talking about color reversal, there's a good reason for not using thiourea based nucleating bath and Haist has talked about it in Volume 2. Thiourea affects dyes and causes yellowing. But here we are discussing B&W reversal and are not concerned about dyes.

As far as shelf life of thiourea solution is concerned, I've a 10% solution that has been around for more than a year and working great. And as far as too much development is concerned, it's a moot point as second development is till completion.

Just for fun I used thiourea nucleating bath followed by second development in Pyrocat PC and got very nice toned slides from an Orwo UN54 roll that I exposed today. As far as my experience is concerned, there's nothing to complain about the thiourea nucleating bath. YMMV as always.
 
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pkr1979

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Just an update her. I made two kind of solutions in January and they are both still fine (tested yesterday). One was the ready to use solution: 4 g in 2 liters 1 % acetic acid (looked a bit weird, but still worked. The other was 4 g in 40 ml 100 % acetic acid. The stannous chloride doesnt really dissolve in the acid, but make sure its somewhat crunched and shaket it up before its mixed with water and it works. There was however what seemed to be some uneven development at the start of the film, on the unexposed part, not the exposed part. This was not the case at the end. I dont know if this has anything to do with the re-exposure bath though... or not. It looks worse on the attached photo then it is, but it will give you an idea. I would expect that to be solid black.
 

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pkr1979

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Might be easier to spot on the exposed first part. The little film part is from the end and is solid black.
 

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YoIaMoNwater

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Just curious, what kind of bleach did you use? Also, what was your second developer? The first photo looks good with the film borders, I wonder if the uneven development could be that your second developer isn’t strong enough.
 
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pkr1979

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Hey. I used dichromat bleach. And the second developer was Dektol 1:2. First photo had longer first developer time but photos came out too fogged. To fogged on the second too to be honest, but not as bad as on first.
 

YoIaMoNwater

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pkr1979 said:
Hey. I used dichromat bleach. And the second developer was Dektol 1:2. First photo had longer first developer time but photos came out too fogged. To fogged on the second too to be honest, but not as bad as on first.
Click to expand...
I’ve had success on TMax400 with permanganate bleach using 1:6 Rodinal as first developer (15 min) and 1:6 HC-110 as second developer (15 min). For both developers, I use constant agitation for 1 min then agitate 10 s for every 30 s. @relistan used his densitometer and got Dmax = 2.95 and Dmin = 0.17. Perhaps you can try that if you have them.
 
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