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Permanganate bleach bath: NaHSO4 instead of sulfuric acid?


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#1 Marc Roessler

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Posted 01 March 2013 - 01:02 PM

For reversal processing of Fomapan, or reveral processing in genereal:

has anybody successfully used a NaHSO4 (sodium bisulfate) solution instead of thinned sulfuric acid for the permangante bleach? Much easier to obtain and easier to handle...


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#2 Kar Wai Ng

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Posted 01 March 2013 - 07:43 PM

While I have nothing to offer in reply to your question, you might be able to get more responses on a forum like APUG.


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#3 Brian Pritchard

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Posted 02 March 2013 - 07:49 AM

I don't know of any formula for using Sodium Bisulphate in bleaches.; I have the feeling that it would not work.  You could check very easily by making up a solution and trying to bleach some processed B/W film.  If the image disappears try redeveloping in some developer such as ID11.

 

Brian


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#4 Marc Roessler

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Posted 04 March 2013 - 03:28 PM

Good tip, Brian. I tried that.. all steps done in daylight.

 

Had a small strip of processed fomapan 100r (processed as reversal).

Bleached that strip with the described solution - worked quite well, silver image gone with small traces of image visible.

 

After that I thought why not try the clearing bath step as well with the sodium meta bisulfite.. unfortunately at this step the image vanished completely, completely transparent base, no trace left of the image at all (very much unlike of what fomapan looks like during re-exposure, which is citron yellow). Even re-developing the test strip did not bring any image back.

 

Any idea what where it went wrong? Did the bleach step work?


Edited by Marc Roessler, 04 March 2013 - 03:29 PM.

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#5 Marc Roessler

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Posted 04 March 2013 - 04:23 PM

Nevermind.. found my error. Of course this strip of film had already been fixed, so no latent silver remained in the emulsion. After bleaching away the already developed silver there's nothing left to re-expose and re-develop.

 

Seems the bleach works like a charm!


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#6 Brian Pritchard

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Posted 05 March 2013 - 04:18 AM

That is good news, I am glad it worked.  There is always a worry about using concentrated Sulphuric Acid.

 

Brian


Edited by Brian Pritchard, 05 March 2013 - 04:19 AM.

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#7 Marc Roessler

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Posted 05 March 2013 - 03:15 PM

Indeed!

  • the acid it is more dangerous to handle and ship
  • one is diluting it anyway so there is no real need to start with concentrated sulfuric acid
  • NaHSO4 is cheap and really easy to obtain. It is also used as a pH value control agent for swimming pools, by the way. Checking needed if it's pure enough, though.

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#8 Richard Tuohy

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Posted 05 March 2013 - 03:17 PM

Hi Marc,

how much sodium bisulphate did you use, and how much P. permangenate?

Interesting that it worked.  well done.

rt


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#9 Marc Roessler

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Posted 06 March 2013 - 03:33 AM

Thanks Richard!

 

4 g KMnO4 (potassium permanganate) dissolved in 1 Liter of distilled water

110g NaHSO4 (sodium bisulphate) dissolved in enough distilled water to form 1 Liter of solution

The permanganate must given some time (with agitation) to fully dissolve.

 

Then mix the two and filter (to remove any manganese dioxide).

 

Should be prepared just before use.

 

I'll try as part of a complete reversal process with some Fomapan 100R soon and let you know about the results.

 

Greetings,

 Marc


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