Bromoil bleach.. help chemists...

[gandolfi]

As some of you know, I constantly make bromoil prints using liquid emulsion as matrix.

There's something strange going on (some times) in the bleach process, that I don't understand..

Normally I get a bleach, where all the silver (blacks) are removed by the bleach. As it should. After rinsing/fix and rinsing, almost no image can be detected.

However, sometimes it looks like only the deep blacks are removed - the image doesn't look bleached and it doesn't matter how long I leave the image in the bleach...
Images made with the exact same chemicals as the ones that dissapear all together...

Anyone can explain this? The image can normally still be inked, but it is hard work, and it looks different.

Also, there's a brown residue left in the bleach after bleaching.. what is that, and is that a good thing or not...

Inquiring minds want to know...

attached two images as they look right after the bleach (but before the final fix, where the warm tone dissapear)...

 

[Perry Way]

I don't work with liquid emulsion so I can't say for sure if I experienced the same thing but in my experience if you use a hardening fixer you get these kinds of results. The matrix is so incredibly hard to get the ink to stick right, even if the bleach step appears to have done its job properly (just like how you mentioned). I wind up only being able to get a slight ghost image in times like that and only using a brayer back and forth rapidly. No brush will work, and also no fancy brush work will work. Only the brayer works (in my case). When I do bromoil now, I stay away from using any normal fixer and I mix up sodium thiosulphate from raw crystals. It takes longer to fix prints this way but then you don't harden the emulsion and thus destroy the ability for the bleach to do its thing later on.

 

[Perry Way]

Oh I just looked at your photos supplied. I have noticed this brownish color before when I allowed the bleached prints to see daylight before the final post-bleach fix. In my case it was exacerbated by using hardened fixer when you fixed the original print. It only took about 1 or 2 minutes of exposure to sunlight for the bleached prints to darken that way for me. I now am prone to using set times that I know work and using my Jobo system so that I can bleach and then fix without reintroducing the print to light. Gene Laughter doesn't think that it is necessary to keep from light so long as you fix shortly after bleaching, but it eases my mind to do so without introducing any light at all between bleach and fix.

 

[cliveh]

Can you please advise what bleach and other bromoil chemical formulation you are using?

 

[gandolfi]

Perry: Thanks for your reply.

However: I always use non hardening fix! (I use Tetenal Vario fix, which is non hardening)

your second comment: The warm colour is normal when using liquid emulsion - it goes away when re-fixing and rinsing.

The (frustrating) thing is, that I used the exact same bleach yesterday, and ALL the image went away - today not...

It is mostly that I don't understand....

CLIVE: sure
for developing I use Tetenal Eukobrom or Tetenal Centrabrom.
Fix: Tetenal vaario fix (non hardening)
Bleach: Copper sulphate - potassium bromide and potassium dichromate....

 

[cliveh]

Perry: Thanks for your reply.

However: I always use non hardening fix! (I use Tetenal Vario fix, which is non hardening)

your second comment: The warm colour is normal when using liquid emulsion - it goes away when re-fixing and rinsing.

The (frustrating) thing is, that I used the exact same bleach yesterday, and ALL the image went away - today not...

It is mostly that I don't understand....

CLIVE: sure
for developing I use Tetenal Eukobrom or Tetenal Centrabrom.
Fix: Tetenal vaario fix (non hardening)
Bleach: Copper sulphate - potassium bromide and potassium dichromate....

Do you use a separate tanning solution, or sulphuric acid as part of above?

 

[gandolfi]

Do you use a separate tanning solution, or sulphuric acid as part of above?

not understood...

The potassium dichromate is the tanning part... (mixed together with the copper sulphate and the pot. bromide)

 

[Photo Engineer]

Gandolfi;

I have observed the same effect with both my own coatings and with commercial coatings. I have seen that it takes place when I suspect higher silver levels (in my coating) or overexposure / overdevelopment in commercial coatings. You see, even though Dmax terminates somewhere around 2.0 in reflection prints, with more development and / or more silver, there is more (but unseen) silver density there.

My boss always told me that in any developer or bleach, Silver Sulfide forms and it is yellow. If you have way too much development (or silver) you can begin to see this yellow Silver Sulfide. To prove this, I coated a lot of silver halide, and overdeveloped it. Then I bleached it and sure enough there was a faint yellow "image" just as you see.

That is the only explanation that I can offer.

PE

 

[gandolfi]

Thanks PE. That does make sense.

But it doesn't explain why it looks like the image isn't bleached away. It is not that the bleach is exhausted I think, as the deepest blacks are gone - but the "middletones" and highlights seems to stay..

 

[cliveh]

Try this -
1) A possible formula for a one part bleach/tanning solution is as follows: -
Copper Sulphate 113 gms
Potassium Bromide 113 gms
Potassium Bichromate 5 gms
Sulphuric Acid concentrated 6 gms
Distilled Water to make 1.8 lt

 

[gandolfi]

Try this -
1) A possible formula for a one part bleach/tanning solution is as follows: -
Copper Sulphate 113 gms
Potassium Bromide 113 gms
Potassium Bichromate 5 gms
Sulphuric Acid concentrated 6 gms
Distilled Water to make 1.8 lt

Clive: I have to ask: why add Sulphuric Acid to the bleach?


UPDATE: I just inked the two images shown in my first post.
They actually ink well - a little harder than usual, but they do recieve the oil as planned. I am happy with the results for two reasons:

1: I like the images... ;-)
2: Even though they sometimes seem not to have been bleached anough, I should't worry - they are still good for bromoil inking..

When the images are dry, I'll make a quick snap and upload it..

 

[Photo Engineer]

Thanks PE. That does make sense.

But it doesn't explain why it looks like the image isn't bleached away. It is not that the bleach is exhausted I think, as the deepest blacks are gone - but the "middletones" and highlights seems to stay..

What you are seeing is a partial image of Silver Sulfide that remains behind due to extremely high density in original Silver metal. If it is Ag2S, it cannot be removed.

My guess anyhow.

PE

 

[cliveh]

Clive: I have to ask: why add Sulphuric Acid to the bleach?


UPDATE: I just inked the two images shown in my first post.
They actually ink well - a little harder than usual, but they do recieve the oil as planned. I am happy with the results for two reasons:

1: I like the images... ;-)
2: Even though they sometimes seem not to have been bleached anough, I should't worry - they are still good for bromoil inking..

When the images are dry, I'll make a quick snap and upload it..

It helps to control the correct pH of the entire solution.

 

[Photo Engineer]

Actually, all Dichromate or Permanganate bleaches must be acidic and must be acidified with Sulfuric Acid. This is because the Silver metal must be converted to Silver Sulfate which begins dissolving in the water. These cannot be rehal bleaches and work with any great efficiency.

PE

 

[Jerevan]

But if all bromoil bleaches must be acidic - then why does some of the recipes show no acid? As far I have understood it, the function of the acid is to soften the emulsion to take the ink better. Never heard of the pH function of the acid in this process - in that case, could you substitute it with whatever chemical that balanced out the pH? At what level should the pH be to be optimal?

 

[Photo Engineer]

Jerevan;

I can only say that dicrhomate does three things. It bleaches silver, it softens gelatin in acid, and it tans gelatin imagewise. Whether all 3 of these are of equal importance or whatever, here, IDK.

PE

 

[gandolfi]

Jerevan and PE: interesting. I have never seen a ewcipie for bromoil printing that contains acid...

And as it might work well for "normal" papers, I don't dare to use it for liquid emulsion papers. The emulsion is soft enough as it is, and I fear, that softer emulsion will make inking impossible....

 

[Jerevan]

There is one in Derek Watkins book, the Gilbert Hopper one and that one is with 10 ml of a 10% solution of sulphuric acid. Emil Mayer also gives a recipe, but with hydrochloric acid. From what Emil says, heavy silver deposits may not bleach fully. And when doing liquid emulsion I guess it would be possible to get these thicker deposits. All of this is theory and reading - I have only used the non-acid bleach, on Foma papers.

On a related note, some of the sensitizer recipes for oil printing contains citric acid.

 

[cliveh]

The proof of the pudding is in the eating and I should imagine there are probably as many different ways/chemical formulations for Bromoil as there are people who make Bromoils. I suppose it's what works for you.

 

[Photo Engineer]

I would have to agree with cliveh. If it woks, why worry. But then Jerevan's comment about silver not bleaching completely is in line with my original comment. I think there is either too much silver or overdevelopment for the bleach you are using.

PE

 

[winger]

I read recently (I've been thinking of trying bromoil) that sulphuric acid can be added to combat the effects of hard water and that you can skip it if your water is soft.