Gainer: do you mean sodium dithionAte or sodium dithionIte?
Say, Gadget, do you happen to know if the density produced by dithionite/bisulfite solution is bleachable (that is, is it metallic silver, or some stable compound)? If it were resistant to bleaching, it might be possible to use that stuff to move the bleach bath to after all developments -- that is, first dev (produces a bleachable image), stop, fogging dev, rinse, bleach, rinse, fix, wash -- and allow use of a self-fixing bleach like Farmer's Reducer, which would combine steps and doesn't damage the gelatin. This *does* work with a sulfiding developer like thiourea (according to one who has done it), but the thiourea also seemingly reacts with the developed silver to make unbleachable highlight density (high Dmin).
Photography has always fascinated me -- as a child, simply for the magic of capturing an image onto glossy paper with a little box, but as an adult because of the unique juxtaposition of science and art -- the physics of optics, the mechanics of the camera, the chemistry of film and developer, alongside the art in seeing, composing, exposing, processing and printing.
A new update!!
I've just come back from my lab, err..., basement (hehehehe) ;-) and it's been two times in a row that a strange thing happens to me.
I usually mix all chemicals using tap water treated with 1g NaEDTA / 1 liter.
All chemicals, including the bleach.
Now, what is happening is that, after all steps (first development, stop, wash, wash, bleach, wash, clearing, wash, redeveloper, wash, hardener, wash, wash, wash) the positive turn very underbleached, with very foggy highlights.
So I've rebleached it (in a new freshly made bleach), recleared and rewashed, and the images turned out reasonably well, although a little washed out.
So here's my question: can the NaEDTA complex the Mn of the KMnO4?
For what I know, the EDTA is a chelating agent forming dative bonds (coordination compounds) only with cations, 'cause the "active" part of the EDTA is the acid (deprotonated): that is the EDTA can complex cations with 2 bonds from N and 4 others bonds coming from COO- (see picture).
So, put this way, the NaEDTA can't complex the MnO4- (I assume that in an aqueous solution exist the equilibrium KMnO4 <---> K+ + MnO4-.
Can be that my sepia redeveloper is too diluited (500mg/250ml)?
Please help, I'm at a loss...
Dithionite, also called hyposulfate as well as hydrosulfite. If you look in the CRC Handbook of Chemistry and Physics, find sodium sulfite and a little farther down you will find sodium hydrosulfite with its synonyms. I don't know where to buy it other than at a supermarket as an additive to detergents to remove or prevent iron stains. I haven't looked to see if it's listed on www.chemistrystore.com.
Originally Posted by Alessandro Serrao
The image is metallic silver.
Originally Posted by Donald Qualls
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Alessandro, I'm not sure what's going on in your soups (I haven't read the entire thread) but EDTA shouldn't form a complex with MnO4-.
Why are you adding EDTA to your developers? That could be throwing wrenches in all the machinery. If there are contaminants in your water supply, used distilled or deionized water...
I've sorted all out using EDTA with tap water only for intermediate washes.
For the rest I use distilled water.
I think my bleach failure was probably due to a cross contamination from the citric acid stop bath and from chlorine or bromine contained in tap water.
It's funny but my trials didn't get me to any useful point so I decided to follow the Ilford method to the letter.
Almost perfect slides, even if I used Tetenal Eukobrom instead of the Ilford PQ Universal (I think the type of first developer is not THAT important - it must be energic) and no emulsion damage with permanganate.
So far I've settle it down to the Ilford method and I'm happy.
I eventually came to the same conclusion. But I found that I needed to reduce the first dev time in the Ilford procedure to get decent-looking slides. I'd imagine that any paper developer could be adapted to the process (with appropriate changes in time, dilutions, thiosulfate concentration, etc.)
Yes, the Ilford method is reliable, providing you follows it to the letter.
And I think the dichromate is not worth the trouble, since the permanganate can be safely used as a substitute: it's paramount to use all solution at ambient temperature, so they can be warm/cold all the same.
I've used Tetenal Eukobrom 1+5 (same diluition of PQ Universal) for 12 min with 3g hypo per 250ml tank. And I've exposed T-Max 100 @ 100. Maybe I was lucky enough but I've obtained beautiful slides, with all details from the blackest shadow to the brightest highlight.
I think Dr5 has not invented the wheel... but that's another story.
Last edited by Alessandro Serrao; 10-07-2005 at 10:59 AM. Click to view previous post history.
As long as you are ultra-consistent in your work, things should go fine for you.
Do you have a film scanner that you can use to show us some results?