[LargeFormat] Removing black spots from prints

[Richard Knoppow]

----- Original Message ----- 
From: "Wilkes, Don MSER:EX" <Don.Wilkes@gems9.gov.bc.ca>
To: <largeformat@f32.net>
Sent: Wednesday, October 15, 2003 2:12 PM
Subject: [LargeFormat] Removing black spots from prints


> The bane of LF has come to bite me in the posterior: dust.
Close inspection
> reveals that a couple of small dust particles must have
been clinging to the
> surface of the 4x5 sheet when I exposed it, resulting in
black spots on the
> print. Naturally, according to the rules of large format,
these appear in a
> large, smooth area of uniform sky...
>
> Does anyone have experience in dealing with this sort of
problem?  I don't
> want to retouch the neg itself -- it's fairly important to
me -- so I'm
> thinking the route to follow will likely be bleaching and
(probably)
> subsequent spotting.  At the moment, I'm using Ilford MG
RC, and I have
> little idea how it reacts to bleaching (nor spotting, for
that matter --
> it's never been my forte).  If it comes to it, I'd
consider switching over
> to fiber-based paper, I guess, but hope that isn't
necessary.
>
> Digital workflow would solve it, but it's not an option,
both for monetary
> and personal preference reasons.
>
> One thing that's worrying me is the first of the batch
that I loaded for the
> Yosemite trip...I haven't souped the others yet, as I
wanted to ensure
> everything was tickety-boo with my processing first.
Also, I've been both
> unusually busy and not feeling all that terrific lately.
Don't want to rush
> nor fumble what may be the only negs I have of that
perhaps
> once-in-a-lifetime trip.
>
> God, I hate dust...
>
> \donw in Victoria, B.C.
>

  Keeping dust out of the holders and camera has been
addressed.
  For removing black spots from prints the best bleach is an
Iodine bleach. This is simply some Iodine dissolved in
alcohol. The Iodine solution is applied with a fine brush
until it has bleached out the spot. The print is then fixed,
prferably in an Ammonium thiosulfate fixer because it is
more efficient than sodium thiosulfate in fixing out the
silver iodide resulting from the bleach. The older formulas
for the bleach used Potassium cyanide as the fixing agent
but it is far too poisonous for general use. A later
version, which I give below, uses Thiocarbamide with the
Iodide and normal fixer. One advantage of Iodine bleaches is
that they don't leave a yellow stain.
  Actually, Farmer's reducer shouldn't stain either if the
print or negative is properly fixed and washed after its
use.

Solution A
Iodine                2.0 grams
Methyl Alcohol       46.0 ml
Shake until completely dissolved

Solution B
Thiocarbamide         4.0 grams
Water to make        46.0 ml

For use take equal parts of each solution. The resulting
mixture may be diluted with water to slow it down. Apply to
the spot and swab off with a cotton tuft wetted with
alcohol. When the redcution is complete refix and rewash the
print.
The makers of SpotTone make a product called Spot Off which
is evidently an Iodine bleach.

---
Richard Knoppow
Los Angeles, CA, USA
dickburk@ix.netcom.com