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