Selective bleaching with Potassium ferricyanide and masking fluid or tape?

Photopathe

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Hi! I have been trying to selectively bleach most of a print with potassium ferricyanide. When I want to bleach a small part only it's a no brainer, I use a brush to apply the bleach just on those parts and it works like a charm. No when I want to bleach almost the whole print and avoid bleaching some small highlights I would like to mask those parts and give a bleach bath to the print. I have been trying with proper latex masking fluid (and they do work for selective toning) but the bleach seems to react with it and leave a bluish stain after removal. I gave it a try with masking tape and even electrical tape but the same happens. Any experience with this? Any advice?
Thanks!
 

pentaxuser

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Which latex masking was this and that it was meant for print masking and can you say how old it is

In all the videos I have seen this latex masking fluid does prevent any bleach incursion and no mention was made of it reacting to create a blue stain

Can you show us the stain and tell us more about bleach dilution, how long it was after the mask solidified that you applied the bleach etc

I take it that this attempt at selective masking is your first attempt?

pentaxuser
 

koraks

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Photopathe said:
I have been trying with proper latex masking fluid (and they do work for selective toning) but the bleach seems to react with it and leave a bluish stain after removal. I gave it a try with masking tape and even electrical tape but the same happens.
Click to expand...

Keep trying different materials until you find one that doesn't use an acid adhesive. That's likely the source of the problem; the acid in the adhesive results in the ferricyanide throwing down a Prussian blue precipitate.
You might also just live with the issue and give the blue-stained prints a brief wash in a weak sodium carbonate solution; this will bleach away the Prussian blue. Any alkaline solution should pretty much work for this. Even selenium toner will probably do away with the Prussian blue stains.
 

nmp

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Intrigued by the blue staining. You would need a source of iron to make Prussian blue - particularly the Fe(II) kind. What's that doing in the glue?

If you haven't already made the prints and trying to change them after the fact, why not burn those areas you want to preserve the density of during printing and do a global bleaching instead.

:Niranjan.
 
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Photopathe

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@nmp Koraks hints that the blue would come from ferricyanide. As for the method I totally agree with you but it still is a nice trick to have up it's sleeve to be able to do this after the fact when you face this situation and it's supposed to be doable. Of course it's no big deal if I can't.

@pentaxuser Here is a picture of the products, as well as the stained prints. The products are almost new. I usually selectively bleach or tone with a brush but yes it is my first attempt at selective masking for a bleach. The bleach I usually use is Farmer's reducer (recipe from Anchell's Cookbook) but sometimes I just trow a teaspoon of ferricyanide in a liter of water and that is what I did in this instance. I applied the masking fluid, waited for it to dry (took maybe 5 minutes) and then bleached for a couple minutes.

@koraks I was very hopeful after reading your reply and I tried it first thing this morning. Unfortunately it didn't work. The picture below was taken after the attempt at the sodium carbonate. I had an oldish 500ml bottle of 10% sodium carbonate lying around. When I saw it wasn't working I added 4 teaspoon of sodium carbonate but to no avail.

From left to right: colourless masking fluid, electric tape, and masking tape.

 

nmp

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I know koraks said that, but ferricynide will not make Prussian blue on its own even in acidic medium without the Fe(II) counter-ion. With the carbonate treatment - at 10%, it should have disappeared instantly if it was cyanotype-like residue.

Looking at your pictures, it looks to me that the prints are also sepia-toned. Is this before you are bleaching or after. The zones where you applied the masks seem more neutral to me than Prussian blue. If you are using straight ferricynide, you also have to fix the print afterwards to remove the silver ferrocynide formed as a result (Farmer's reducer contains thiosulfate to do the job.)

If you can add more details on your process, it will be helpful to diagnose the problem.

:Niranjan.
 

pentaxuser

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Here's something of a longshot by way of a solution. When I googled masking fluid all I could find was masking fluid for painting so is there any chance that your masking fluid is not as impermeable as it needs to be for bleaching?

I recall seeing a video by an Ilford Master Printer called Dave Butcher in which he describes his latex fluid as completely impermeable when dry and he uses it for selective bleaching and toning. It's called Fotospeed MK50 Masking Fluid. It requires that you use Fotospeed MKS Brush Cleaner for the brush which indicates its nature If you can clean your brush with ordinary water this may indicated that the masking fluid isn't right for selective bleaching

This stuff is made by a U.K. company called Fotospeed so whether what there is that is an equivalent in Canada I have no idea

Anyway here is his video and the interesting part comes at about 9 mins where he describes selective bleaching and toning of statues on the Trocadero in Paris


pentaxuser
 
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Photopathe

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Thanks Pentaxuser! Interesting. I am unable to clean a brush if I use it for the latex masking fluid but I use a metal applicator.
The problem is solved, it works after all.
Thank you very much @nmp !
In answer to your queries, the leftmost print is Fomatone 131 toned in Selenium 1+3 for 2 minutes. That paper gives a purplish brown with a strong selenium dip, mostly brown at some point. The middle print is Ilford Cooltone and I think I didn't tone it but I am not sure anymore as it does look warm (maybe the developer). The print to the right is Adox semi-matt and that one I am sure was not toned. I fixed it for a minute and took another picture that I attached here. If you compare to the one above you clearly see there is no difference in tone anymore, it's just darker where it was masked. So you obviously nailed it with that comment:
"If you are using straight ferricyanide, you also have to fix the print afterwards to remove the silver ferrocyanide formed as a result"
I guess I have been a bit sloppy this time around. I should have remembered that it was not a good idea to bleach locally after toning. As for fixing, I am usually more methodical but these were test that were to end in the trash bin anyway so I didn't fix after the bleach and I didn't know it could have that consequence (formation of silver ferrocyanide). You were also right that the masked parts were not blue after all but neutral bluish. The contrast with the brown of the rest of the picture gave me that wrong impression. Also the first time I tried I used the blue masking liquid so it was easy to jump to the conclusion that there was a blue stain from it and then the idea of the blue patch stuck with me.

Thanks again for all the inputs!

 

nmp

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I am glad it all worked out. It's nice to have the process in your bag of tricks for use when needed.

:Niranjan.
 
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Photopathe

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As a side note, the bleach has an interesting cooling effect on the very warm Fomatone paper. Much more so the raw ferricyanide bleach than Farmer's reducer. It doesn't make it as neutral as Ilford Classic as there is a cream paper base anyway but much more neutral than without the bleach.
 

pentaxuser

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Yes glad you have solved the problem but what exactly was the solution to the problem, Photopathe?

Thanks

pentaxuser
 
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Photopathe

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The problem was not exactly what it seemed to be. The masked part gave the impression it was blue stained but it was in fact neutral-bluish. I bleached in a plain ferricyanide bath and I removed the mask after a quick dip in the fixer. Proper fixing after the bleach (with the mask removed) eliminates the silver ferricyanide that was formed and the bluish tint of the previously masked part.
It really did solve the problem but one thing still seems a bit odd to me. You would think that if the bleach has this effect on the masked part it would also partly bleach the masked part and also that is the bleach reaches the masked part (through the paper?) the fix also would and that the problem would not have occurred in the first place. So problem solved in practical terms but I am left with some interrogations.
 

pentaxuser

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Thanks for 13 I now understand. Proper fixing post bleaching removes the bluish tint. I have never tried bleaching so have no experience but it just seems to me that if proper photographic latex masking makes hte part that is masked impermeable to the bleach the provided the bleach is thoroughly washed off and the bleached part is properly fixed then the part covered by the latex mask should have remained as it was so when the mask is rubbed off nothing more is required and the process is finished

I have just never heard of the bleach reacting with the mask or penetrating under the latex, nor have I heard anyone complaining of this effect with Fotospeed's latex masking fluid. OK because I haven't heard of it happening doesn't mean that it hasn't happened

I still wonder if the masking fluid was in fact impermeable to bleach especially if it was strong bleach

pentaxuser
 

Rich Ullsmith

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Rubber cement and hexane, both of which should be at a decent art supply. Mix hexane and rubber cement in a ventilated area. Apply with a hobby paint brush. Hexane thins the rubber cement so it is very easy to control. No mention in this thread about rc vs. fiber masking. Hexane and rubber cement is money for rc paper, can't speak to fb.
 
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