Concentrate and Working Solution for E-6 Reexposure Bath Based on Kodak's US5948604A

Rudeofus submitted a new resource:

Concentrate and Working Solution for E-6 Reexposure Bath Based on Kodak's US5948604A - E-6 reexposure bath formula derived from patent US5948604A

Kodak provided a "teaching patent", i.e. a publication for preservation of knowledge, for their 5 liter E-6 home processing kit. The original patent text can be seen here. While anyone with access to these formulas and ingredients could start mixing and using, this article tries to make these formulas more accessible to amateurs. Please note, that all liquid ingredients except for dilute aqueous solutions and water are given in...

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This is very interesting, spells it all out with dilutions, etc. I haven't tried yet, but I suspect most amateurs will have no hope of getting many of the chemicals needed. Thanks for posting this!

If you need a reexposure bath mixed from "amateur ingredients", then here is what I would use:

Ingredient/Target	250ml	500ml	750ml	1000ml
Water	200ml	400ml	600ml	800ml
EDTA free acid	0.75g	1.50g	2.25g	3.00g
NaOH 25% w/w solution	8ml	16ml	24ml	32ml
Acetic Acid 10% w/w solution	38ml	75ml	113ml	150ml
SnCl2* 2 H2O	0.25g	0.50g	0.75g	1.00g

I would mix this bath fresh, beware of sudden death!

If you want to mix the long lasting concentrate, then you may be able to pester Suvatlar or Formulary into supplying you with Dequest 2000 or Dequest 2006. The other ingredients should also be available from at least these two.

Dear Rudeofus, I am sorry to interrupt again, but in the process of configuring the concentrate, I have encountered some problems. Stannous chloride is hydrolysed to a precipitate when dissolved. For the first development, there is also a precipitate when potassium hydroxide is dissolved during the configuration process.

Stannous chloride solutions are unstable. I think the common solution is to include metallic tin (powder, pellets) in the solution to counter this problem.
Personally, I've not seen problems with precipitate in freshly mixed stannous chloride solutions, but I've only ever used it in experiments with tinning copper pads and traces on PCB's in combination with thiourea. As I recall, this solution was also not stable.
Can you confirm you did use a sequestering/chelating agent (EDTA in this case)?

@fert Like many metal ions stannous ion will form a hydroxide precipitate, if you add something alkaline such as Potassium Hydroxide. You have to make sure, that the stannous ions are fully complexed (with EDTA, ATMP or DTPA) before you add the hydroxide.

Now here's the risk: if you mix Stannous Chloride and EDTA free acid, the EDTA will not dissolve, because EDTA free acid is insoluble and the Stannous Chloride will also be acidic. In order to dissolve the EDTA you have to add alkali, and if the reaction between alkali and stannous ion is faster than the dissolution of the EDTA, then Stannous Hydroxide precipitate will appear and remain. It's a bit tricky, but now that I described the competing reactions going on, you will quickly find a way to get this working. And yes, my reexposure bath concentrate always looks a bit milky, but that's ok, it always worked fine.

PS: Someone once suggested "just use a tea spoon of Sodium Dithionite in a liter water" as reexposure bath. If you don't have access to good sequestering agents. If you use dithionite solution as reexposure bath, make sure you mix it fresh, it only lasts for a few hours.

Now that I expressed myself in the Pre-bleach and bleach section now I come here haha.

Here it is difficult to get ATMP in any of its forms, they only sell it in 200lt drums. So I was researching another product that works as a sequestrant of copper, iron, and zinc ions. and I came across HEDP (ethidronic acid) which can perform the same function, I even read that ATMP works better in solutions whose pH is 2 or 3, HEDP works better in solutions with pH 4 or 5, so here where I live you can buy HEDP as a stabilizer for hydrogen peroxide solutions in cleaning products, so it's cheap and easy to obtain. It is a 60% solution.

Now, speaking regarding the reversal bath. The formula I used was the following:

HEDP (60%) 1.5ml
Hydroxylamine sulfate 0.05gr
Citric acid 9gr
Stannous chloride dihydrate 0.8gr
Sodium acetate 5gr
Sodium hydroxide 5gr

Mix everything exactly in the following order, in a volume of 100ml of water and then add water to a volume of 500ml.

This formula is taken from the Russian document Shadrin, which took this formula from the company Konishiroku Photo Industry. Adding the stannous chloride in small portions with vigorous stirring, a precipitate forms.

Shadrin mentions that you have to let the solution rest and then filter the precipitate. In my case, although a precipitate forms after adding the stannous chloride, when you let it rest, The precipitate disappears, the mixture, which at first is somewhat cloudy and milky, becomes colorless when left to stand for about 15 minutes. My question now is, in his experience @Rudeofus , what is the useful life of this work solution?

One last thing, when I perform a reexposure bath the pH of my color developer must be 11.9. Note that when using this reversal bath I must lower the pH to 11.7 since otherwise the final result will be a slide that is too green.

Josaw98 said:

In my case, although a precipitate forms after adding the stannous chloride, when you let it rest, The precipitate disappears, the mixture, which at first is somewhat cloudy and milky, becomes colorless when left to stand for about 15 minutes. My question now is, in his experience @Rudeofus , what is the useful life of this work solution?

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This is a surprisingly difficult question and it reminds me a bit of the XTol situation: Stannous Chloride is an incredibly powerful fogging agents, and even tiny traces of this stuff will fog your film. At the same time it is a powerful reducer and happily reacts with Oxygen from air. So in practice it will work forever until it all of a sudden doesn't. I have mixed a concentrate and it lasted for many months, but there's always that trace of risk. Obviously there is more Oxygen per Stannous Chloride in working solution than in concentrate, so the working solution may be even riskier.

Here is what you can do: if your reexp soup has gotten a bit old and you start asking yourself about it, then put an unexposed clip of any film into a film tank, soup it in that reexp for a minute, wash thoroughly, then soup it in developer and fixer. If that film comes out pitch black, then the reexp should be good enough for E-6.

Now if you remember the XTol story, there were legends that people did a clip test right before and still pulled out blank negatives, but at some point we have to accept, that photography is a risky business, and whoever hasn't messed up a roll shall cast the first stone. All the film rolls I have messed up were not trashed because of failed reexp, so the risk with faulty reexp may well be overblown. Be prepared, though!

Hi all
Sorry for didn't noticing this discussion
For the SnCl2 problem
First, if you refer to the order and ingredients of the patented document , there is no problem,

but what is prone to problems is that the quality of SnCl2 you bought may not be good(I met this problem even bought the most expensive and quality brand here).

That is why I suggest you use HCl (very thin resolution) to test it, if there is a situation that it can't be dissolved, it means that the quality of your chloride is not good

ATMP 5NA is very important. If you can't buy it, you can try to replace it with ATMP and use sodium hydroxide to pull the pH value to the correct value. This should be feasible,But I have never tried it

@czygeorge The chemistry market in Europe and North America works very very differently from what other people in the rest of the world would experience. If we want to buy chemistry, then we are basically demoted to beggars. "Please please sell my Hydroquinone, I pinky promise that I won't poison my neighbor's cat with it". Like that.

There are some enterprising outfits like Suvatlar, Artcraft and Formulary, who seem to fight a herculanean struggle to supply us. Some of them offer CD-3 but not CD-4, strong sequestering agents are not to be found on any price list, but sometimes available when asking. You can buy 37% Sulfuric Acid in liter bottles in auto stores without questions asked, but nobody will sell you ATMP "because it's an acid". I had to buy "Thioglycolic Acid Sodium Salt", because they would not sell me "Thioglycolic Acid".

The chemistry you do get is often of very questionable quality. My batch of Sigma Aldrich branded Sodium Thiocyanate turned magenta red over time, and Sigma Aldrich could not even tell me about the impurities in their product (it was Iron). If your batch of SnCl2 is pure crap, then you try to make do with this crap, since this is the only SnCl2 you'll find. Oh, you'll find many sources, but most of them won't sell to private individuals.

The chemistry market in Europe and North America is completely broken, that's why there are only few hobbyists, and why most of the world's chemical industry went to China and India. I am sure, that our environment flourishes, if instead of doing stuff in the dark room we take our SUVs to the shopping mall to buy a trunk load of junk.

I have some tin chloride at hand, but haven't used it for anything photographic. I bought it without too much trouble (I may have registered as a business account, IDK). Don't know about the purity. Bought it for PCB making.

koraks said:

I have some tin chloride at hand, but haven't used it for anything photographic. I bought it without too much trouble (I may have registered as a business account, IDK). Don't know about the purity. Bought it for PCB making.

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Suvatlar sells Tin II Chloride. It never fully dissolves even with ATMP, the liquid always stays cloudy, but it works very well. He's the only source of Tin II Chloride for private individuals like me, so I am not going to complain (except about the general state of chemical supply in EU).

Rudeofus said:

@czygeorge The chemistry market in Europe and North America works very very differently from what other people in the rest of the world would experience. If we want to buy chemistry, then we are basically demoted to beggars. "Please please sell my Hydroquinone, I pinky promise that I won't poison my neighbor's cat with it". Like that.

There are some enterprising outfits like Suvatlar, Artcraft and Formulary, who seem to fight a herculanean struggle to supply us. Some of them offer CD-3 but not CD-4, strong sequestering agents are not to be found on any price list, but sometimes available when asking. You can buy 37% Sulfuric Acid in liter bottles in auto stores without questions asked, but nobody will sell you ATMP "because it's an acid". I had to buy "Thioglycolic Acid Sodium Salt", because they would not sell me "Thioglycolic Acid".

The chemistry you do get is often of very questionable quality. My batch of Sigma Aldrich branded Sodium Thiocyanate turned magenta red over time, and Sigma Aldrich could not even tell me about the impurities in their product (it was Iron). If your batch of SnCl2 is pure crap, then you try to make do with this crap, since this is the only SnCl2 you'll find. Oh, you'll find many sources, but most of them won't sell to private individuals.

The chemistry market in Europe and North America is completely broken, that's why there are only few hobbyists, and why most of the world's chemical industry went to China and India. I am sure, that our environment flourishes, if instead of doing stuff in the dark room we take our SUVs to the shopping mall to buy a trunk load of junk.

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Dear Rudeofus
So sad and sorry to hear thatAnd really respect to you guys
Hope Kodak(new manufacturer) could recontinue their Kodak E-6 again to make this situation better

Rudeofus said:

Suvatlar 销售二氯化锡。即使使用 ATMP，它也不会完全溶解，液体总是浑浊，但效果很好。他是像我这样的个人二氯化锡的唯一来源，所以我不会抱怨（除了欧盟化学品供应的总体状况）。

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我发现，通过将反转溶液加倍并将比例从 1:39 改为 1:19，液体会更清澈，不会浑浊。