Re: altered dektol

[Richard Knoppow <dickburk@ix.netcom.com>]

At 12:56 PM 08/12/2001 -0600, you wrote:
>Hi:
>
>I did some fiddling around in the darkroom seeing if I could turn dektol
>into a low-contrast developer suitable for making high contrast ortho film
>behave like a standard continuous tone film.
>
>I've had pretty good success.  I used Kodak Camera 2000 CGP ortho film and
>started with standard dektol.  As a test subject I contact printed a
>fairly contrasty tri-x negative with lots of highlight and shadow detail
>- a picture of the falls in Johnston Canyon in Banff.
>
>I started by adding baking soda to straight dektol.  This produces a lower
>contast image, but is too contrasty for an interpostitive.  It may work
>for producing pinhole negatives from a very low contrast scene.
>
>Increasing the volume of baking soda decreases the contrast up to a
>certain point, after which additional baking soda does not change the
>contrast - it just clumps in the bottom of the tray.
>
>Next I tried adding small volumes of stop bath to the developer.
>This decreased the contrast some, but not to the same extent as baking
>soda.
>
>I had best success with baking powder.  My understanding of baking powder
>is that it is supposed to produce carbon dioxide when added to water.  It
>does this by having a mixture of sodium bicaarbonate and some other
>chemical(s) to produce a slightly acidic solution so that the sodium
>bicarbonate dissociates to produce carbon dioxide.
>
>The same slightly acidic environment is needed to slow the activity of the
>developer to turn it into a low contrast developer.
>
>I used "Magic Baking Powder" a Nabisco product.  Its ingredients are (in
>order)
>
>corn starch
>monocalcium phosphate
>sodium bicarbonate
>
>I diluted the dektol 1:1 with water
>
>100 ml dektol
>100 ml water.
>
>I then added two teaspsoons of baking powder.  The developer turned
>white and fizzed.  There was a powdery suspension in the developer - I
>assumed it was the corn starch.
>
>This produced an image with similar contrast to the baking soda + dektol.
>
>I added another two teaspoons of baking powder. (total of 4 teaspoons
>baking powder) This produced an image with even lower contrast.  There was
>also a distinct loss in film speed.  This was even lower contrast than the
>previous but still too contrasty.
>
>I added another 2 teaspoons of baking powder and increased the exposure
>1/2 stop.  this gave a good low contrast image but still underexposed.
>
>I did a proper test strip.  All the initial test exposures were 10 seconds
>long. The correct exposure for the developer now was 60 seconds.
>
>I exposed another test for 60 seconds and developed it for 3 minutes.
>(All previous test were developed for one minute)
>
>I was able to get an image with very good shadow details in the dark rocks
>of the image and still hold all the highlight details in the water
>cascading over the falls.
>
>So far good success with:
>
>100 mls Dektol
>100 mls water
>6 teaspoons Magic Baking Powder
>
>To produuce "normal" contrast images using high-contrast ortho film.
>
>Gord
>
> ---------------------------------------------------------
>Gordon J. Holtslander		Dept. of Biology
>holtsg@duke.usask.ca		112 Science Place
>http://duke.usask.ca/~holtsg	University of Saskatchewan
>Tel (306) 966-4433		Saskatoon, Saskatchewan
>Fax (306) 966-4461		Canada  S7N 5E2
>---------------------------------------------------------
>
  I wonder why you start with a fundamentally high contrast developer like
Dektol. Adding the bicarbonate mainly acts to lower the pH, whick lowers
the activity somewhat. 
  I think better success would be had by using a lower activity developer
to start with.  There are a number of lower contrast developers which might
be suitable. The choice depends on just how high contrast the film is to
begin with and how much contrast is desired in the negatives. 
  Emulsion contrast is determined mostly in the manufacture. It is a
function of the range of sensitivity of the silver halide crystals of which
the emulsion is made. The wider the range, the lower the contrast. Very
high contrast emulsions are made so that nearly all of the halide crystals
have the same threashold of exposure between developable and non
developable states. 
  A very low contast developer can discriminate among these crystals more
than a high contrast developer does. 
  Most of the really low contrast developers, like POTA or Kodak Technidol,
depend on the very low contrast characteristic of Phenidone, and its
derivatives, for their operation. For normal contrast Phenidone must be
combined with another developing agent, usually Hydroquinone. Without the
superadditivity effect of Hydroquinone or ascorbic acid the contrast is
extremely low. 
  As far as Dektol, if you want to experiment try adding some common salt
to it. Salt is a silver solvent and restrainer. Its the basis for Kodak
Microdol-X and Ilford Perceptol (they are nearly identical). I have no idea
of how much to add. I suggest using kosher salt rather than table salt
because table salt usually has iodide and other additives in it. 
  To be practical you might try something like Kodak D-23, or even
Microdol-X. Technidol probably would work but is very expensive. It is
essentially POTA with wetting agents in it to help get better uniformity
from the extremely thin Technical Pan emulsion. 
----
Richard Knoppow
Los Angeles,Ca.
dickburk@ix.netcom.com