Mixing Potassium Ferricynide

[Alan9940]

Just received an order of Potassium Ferricynide from Photo Formulary which I plan to use for experimenting with David Katchel's SLIMT techniques. I've never used this particular chemical. Should I warm the water for mixing or will it dissolve into solution properly in room temp water?

Thanks for your help!

 

[Ian Grant]

It dissolve easily but it's worth warming the water slightly, and use distilled or deionised for Latent image bleaching, tap water can contain Chlorine,

Ian

 

[Alan9940]

It dissolve easily but it's worth warming the water slightly, and use distilled or deionised for Latent image bleaching, tap water can contain Chlorine,

Ian

Thanks, Ian. Definitely will be using distilled water.

 

[Doremus Scudder]

I use SLIMTs often, plus I do bleach/redevelop from time to time and use a rehalogenating bleach (potassium ferricyanide and potassium bromide) for routine print bleaching.

I recommend mixing stock solutions of both ferricyanide and bromide like David Kachel recommends. 500ml each of a 10% ferricyanide solution (Solution A) and a 3.3% bromide solution (Solution B) will get you started (I mix liters and they last for ages - maybe you don't need so much to start with). Then, you can measure out what you need more easily and conveniently, just adding the small amount of each to the desired amount of water. An example from my SLIMTs: to make 500ml of a 0.02% ferricyanide/bromide solution, take 1ml each of the two stock solutions to a total volume of 500ml. I use small graduated syringes to measure the small amounts with. Note that the 0.02% is just for the ferricyanide; the bromide content is much less. The beauty of having the two stock solution at different strengths is that you always use the same amount of each when mixing the solutions.

For bleaching prints, I usually make a weak solution of ferricyanide from the stock and then add three times the bromide stock, i.e., 1 part Solution A, 3 parts Solution B and whatever amount of water needed to make the strength needed for bleaching (I'm kind of slapdash here; usually measuring in "eyedropper-fuls" into a graduate and adding water till the color looks right, then adjusting as needed).

Hope this helps,

Doremus

 

[Alan9940]

Thanks, Doremus, for the detailed reply. I'm really looking forward to experimenting with SLIMT to tone down the contrast of Adox Lupex contact printing paper. I really, really like this paper, but many times find its contrast to be just slightly too much. I'm hoping the working Potassium Ferricynide pre-bath will reduce the contrast by 1/3 - 1/2 grade. Based on my reading, I feel pretty confident that with dilution and time I can achieve exactly what I'm looking for.

 

[Doremus Scudder]

Alan,

Your response begs the question: If the paper seems "too contrasty," why don't you try some other things first before SLIMTs. First and foremost is to simply develop your negatives to a lower contrast gradient so that they print well on the paper. The second would be to use a print developer that gives less contrast. There are a number of formulations.

I take it that you are contact printing. Have you checked out the advice on michaelandpaula.com? The site is still up even though Michael passed away recently. They have a number of developer suggestions and tips for getting the contrast right on Azo/Lodima/Lupex.

SLIMTs will work if none of the other things do, however.

Best,

Doremus

 

[Alan9940]

Doremus,

I have tried other things... For example, I've played with a water bath following Amidol, but Amidol is such a powerful developing agent that even with a very short dip in it (say, 15-20 secs) followed by the remainder of the time in water, I still could not get exactly what I wanted. I've tried a Selectol Soft equivalent and Defender-59D, both soft working developer formulas, as the sole print developer. Again, can't get exactly what I want out of it. So, yeah, I've tried some things. About the only thing I haven't experimented with, other than SLIMT, is pre-flashing the paper, but I'm thinking SLIMT may give me more control.

Yes, I am contacting printing 8x10 negs. I haven't played around too much with development time changes because 1) I like a nice robust negative, and 2) I like a versatile negative rather than one tailored to a specific paper. For example, I have a box of grade 2 Lodima that I, basically, don't use nowadays because it would require a pretty high contrast negative to print properly on that paper. Heck, I've even printed a couple of my negs intended for pt/pd printing on that grade 2 Lodima and even that's not enough contrast! What it boils down to with Lupex is that I'm pretty close using it as is, but would like to knock just a smidgen off the contrast.

And, yes, I'm familiar with Michael and Paula's website. Michael was very helpful to me in the past via his forum and e-mail. A very generous individual for sure!

 

[Doremus Scudder]

Alan,

I figured you'd probably exhausted other possibilities, but didn't know for sure and had to ask

SLIMTs should do the job, but you'll spend some time dialing in the proper time and dilution. Once that is done, you can likely have a really flexible system.

Best,

Doremus

 

[Alan9940]

Alan,

I figured you'd probably exhausted other possibilities, but didn't know for sure and had to ask

SLIMTs should do the job, but you'll spend some time dialing in the proper time and dilution. Once that is done, you can likely have a really flexible system.

Best,

Doremus

Hey, I'm always glad when somebody asks because these old synapses ain't what they used to be!

Since you seem to be my resident SLIMT expert, I have a small question after working in the darkroom this morning playing around with this technique. When using the potassium ferricynide working bath during a printing session, is a single bath good for only one sheet of paper, then I mix fresh for the next sheet? If it's good for multiple sheets, about how many per liter of working solution?

Thank you for your help.

 

[MattKing]

FWIW, David Kachel (creator of SLIMT) posts from time to time here on Photrio.
So if you are looking for another "resident" expert ...

 

[Doremus Scudder]

Hey, I'm always glad when somebody asks because these old synapses ain't what they used to be!

Since you seem to be my resident SLIMT expert, I have a small question after working in the darkroom this morning playing around with this technique. When using the potassium ferricynide working bath during a printing session, is a single bath good for only one sheet of paper, then I mix fresh for the next sheet? If it's good for multiple sheets, about how many per liter of working solution?

Thank you for your help.

As Matt mentions, David Kachel is the real resident expert. I only use SLIMTs for negative contractions; I've never really had reason to use them for print paper, though I may in the future. With negatives, I'll run a batch through one bath, which for me is maximum six 4x5 sheets in 500ml of solution. I discard the SLIMT bath and mix fresh after that, since I'm using really weak dilutions (e.g., 0.01% or less).

You could certainly try to run several prints through the SLIMT bath; any exhaustion should be fairly easy to spot. I'd likely first test for usable SLIMT times by running a bunch of test strips of a known negative or of a step wedge through a SLIMT bath of x dilution, pulling the strips and tossing them into the developer at regular intervals, say every 30 seconds after the first two minutes. This should give you a range of useful times. Changing dilution and repeating will give you even more. I'd then run a bunch of identical small prints in a rather small amount of SLIMT solution (say 4x5 prints in 500ml of solution) at my time and dilution for greatest desired contrast reduction. I'd put the prints through one-at-a-time and keep going till I saw a change in contrast. There you have the capacity of your SLIMT solution. Add a safety factor and scale up for larger prints, et voilá, you're in business.

Best,

Doremus

 

[Alan9940]

You could certainly try to run several prints through the SLIMT bath; any exhaustion should be fairly easy to spot. I'd likely first test for usable SLIMT times by running a bunch of test strips of a known negative or of a step wedge through a SLIMT bath of x dilution, pulling the strips and tossing them into the developer at regular intervals, say every 30 seconds after the first two minutes. This should give you a range of useful times. Changing dilution and repeating will give you even more. I'd then run a bunch of identical small prints in a rather small amount of SLIMT solution (say 4x5 prints in 500ml of solution) at my time and dilution for greatest desired contrast reduction. I'd put the prints through one-at-a-time and keep going till I saw a change in contrast. There you have the capacity of your SLIMT solution. Add a safety factor and scale up for larger prints, et voilá, you're in business.

Yep, I know Mr. Kachel is the father of SLIMT, but in all the years I've been hanging around here I can't say I've seen his name popup all that often. Perhaps, he'll see this thread and jump in...

Thanks for your suggestions. In my playing around, yesterday, with this technique on paper I think I've arrived at a baseline time/dilution to achieve exactly what I'm looking for with Adox Lupex. My thinking, at the moment and why I asked about the possible number of prints one bath might support, is to start at my baseline time/dilution, then increase working concentrate and/or increase time, as needed, to further reduce contrast. Assuming multi prints could go through a single bath--and I'm probably talking less than 6 sheets of paper--I'd effectively have a very easy way to control contrast, at least to one grade lower; probably wouldn't ever need more than that. Anyway, it's great fun experimenting and I'm excited to have another tool at my disposal when crafting silver prints!

 

[Doremus Scudder]

Yep, I know Mr. Kachel is the father of SLIMT, but in all the years I've been hanging around here I can't say I've seen his name popup all that often. Perhaps, he'll see this thread and jump in...

Thanks for your suggestions. In my playing around, yesterday, with this technique on paper I think I've arrived at a baseline time/dilution to achieve exactly what I'm looking for with Adox Lupex. My thinking, at the moment and why I asked about the possible number of prints one bath might support, is to start at my baseline time/dilution, then increase working concentrate and/or increase time, as needed, to further reduce contrast. Assuming multi prints could go through a single bath--and I'm probably talking less than 6 sheets of paper--I'd effectively have a very easy way to control contrast, at least to one grade lower; probably wouldn't ever need more than that. Anyway, it's great fun experimenting and I'm excited to have another tool at my disposal when crafting silver prints!

Alan,

I believe you have a good approach. I think you can find a dilution for which you then could simply bleach the prints for different times and have a wide variety of contrast reductions at your fingertips. Doing the capacity test will let you know exactly where the limits to through put are.

Here's David Kachel's web page with his monographs. They are worth perusing. http://davidkachel.com/wpNewDK/?page_id=8

His work is at DavidKachel.com

Best,

Doremus