Potassium Ferricyanide question

[Fred L]

Me again.

Been a few years since I've used potassium ferricyanide for local bleaching. I remember dabbing the print with q tips etc., and keeping a hose running nearby to clean it off, now and then.

The question I have is do I need to refix the print after doing local lightening with the stuff ? I also presume you can't use potassium ferricyanide on prints that have been toned in selenium ?


tia,
freddy

[Vaughn]

It has been awhile for me, also, but yes, fix after bleaching...expect the bleaching to go a little further when the print hits the fix. A good re-fix and wash will be needed, esp if selenium toning.

Bleaching a selenium toned prints is not the usual way to go about it. Although it might technically 'work', I imagine difficulties in even bleaching and color shifts if those are an issue.

[Merg Ross]

Vaughn has given a good answer.

You may also find this helpful; scroll down to #10 & #11 for tips from Bruce Barnbaum. He is skilled at the process.

https://unblinkingeye.com/Articles/Printing/printing.html

[John Layton]

Also use extreme caution if you are using ferricyanide for the retouching of black spots. First, use as weak a dilution as time will allow (otherwise, long after applying retouching fluid to the bleached white spots on the dry print, you might be horrified by seeing some of those spots reappear!:eek:), but do not let too much time intervene if you are "spot refixing" in cases where you have a large number of black spots to bleach - otherwise you may find that you've created blobs of lightened areas...not from the migration of excess ferricyanide, but from over-fixing. At any rate - just be really careful!

[Fred L]

thanks everyone, and thanks Merg for the Unblinkingeye's bit about Bruce Barnbaum's process, extremely helpful.

[Hans Berkhout]

Lootens on photographic enlarging and print quality, 8th edion Chapter 10 devoted to reduction, quite informative.

[Ulophot]

Since I print on warmtone papers, the linked potassium iodide and iodine bleach solution looked interesting. I probably don't need it; I have bleached successfully with ferricyanide. However, Photographers Formulary requires a DEA form for the first, and doesn't list iodine, so I guess I'll stick with what I know, unless someone has experience with this.

[esearing]

If you add equal parts PF and Potassium Bromide you get a reducing bleach which is slower acting. I have not noticed color shifts except when using selenium after bleaching a dark area which has been noted. I remember seeing a video once where the artist purposefully overprinted his images , spot bleached certain areas, then gave the whole print a quick dip in a dilute bleach . when dry it came back with more sparkle/local contrast and no apparent local bleaching marks. It may have been a specific technique for the paper he was using.

[Ulophot]

esaring, well now we're talking! PF and PB are exactly what I use for the SLIMT pre-bleaching technique I use. I should have thought of it myself. Thank you. You've earned your keep and may take the rest of the week off.

[Doremus Scudder]

esaring, well now we're talking! PF and PB are exactly what I use for the SLIMT pre-bleaching technique I use. I should have thought of it myself. Thank you. You've earned your keep and may take the rest of the week off.

I use the same stock solutions of potassium ferricyanide (10%) and potassium bromide (3.3%) that I use for SLIMTs for mixing the same rehalogenating bleach esearing mentions. Works well and can be (somewhat) reversed by redevelopment in the print developer if it goes a bit too far.

FWIW, my bleaching technique is really similar to what B. Barnbaum does in the video. Important is a good rinse after the fix to remove fixer in the emulsion or the bleaching may be speeded up and redevelopment not possible (the residual fixer fixes the re-halogenated compounds as they are made, à la Farmer's Reducer)

Best,

Doremus

[Ulophot]

[QUOTE=FWIW, my bleaching technique is really similar to what B. Barnbaum does in the video.
[/QUOTE]

What video, please? I don't see a link to one in this thread.

[esearing]

esaring, well now we're talking! PF and PB are exactly what I use for the SLIMT pre-bleaching technique I use. I should have thought of it myself. Thank you. You've earned your keep and may take the rest of the week off.

thanks - I'll tell my boss. Revision My reducing bleach for redevelop is not equal parts. Or make a 1% PB solution and add the PF to it. PB comes in handy for developer tweaking.

Potassium Ferricyanide . . . . . . . . . . . . . . 20 g
Potassium Bromide . . . . . . . . . . . . . . . . . 10 g.
Water to make . . . . . . . . . . . . . . . . . . . . . 1 litre
Dilute even further for slower action or spot use. Dark yellow for rapid, light yellow for slow.

[Doremus Scudder]

What video, please? I don't see a link to one in this thread.

My fault, Philip. I thought the link posted earlier was to a video of Barnbaum demonstrating his bleaching technique (I've seen one somewhere, but couldn't find it quickly). It was to an article instead.

Here's a link to a Tim Rudman video. The bleaching portion is at about 5:20. I'm not sure if he's using a rehalogenating bleach, but the techniques are the same.

Best,

Doremus

[Ulophot]

Doremus, you appear to have infringed on my copyrighted trick of failing to include the cited link. My lawyer will be in touch early Sunday morning.

[Doremus Scudder]

Doremus, you appear to have infringed on my copyrighted trick of failing to include the cited link. My lawyer will be in touch early Sunday morning.

Details, details... :)

Here's the link: https://www.youtube.com/watch?v=em4LxWxy_Is

Doremus