From: Larry on 24 Jul 2008 18:33
Does anyone out there have the perceptol formula? If you do, could
you send to my e-mail. thanks....
From: Richard Knoppow on 24 Jul 2008 21:34
"Larry" <l_kriese(a)canoemail.com> wrote in message
> Does anyone out there have the perceptol formula? If you
> do, could
> you send to my e-mail. thanks....
The formula for Perceptol is proprietary. Perceptol is
evidently very similar, if not identical, to Kodak
Microdol-X. I have somewhere a patent which I believe is for
Microdol but will have to search for it. Both are low pH
developers which rely on sodium chloride (common table salt)
as the fine grain agent. Microdol-X evidently contains a
silver sequestering agent to prevent dichroic fog, otherwise
a problem for this type of developer. Its very likely
Perceptol has the same thing. My experience with Perceptol
is that it produces very clean negatives. If I can find my
guess at the Microdol formula I will post it but both of
these developers are similar to Kodak D-23 with about 25
grams of sodium chloride added.
I have no idea of what the sequestering agent is,
possibly a mercaptan but Kodak has many patents for
anti-silvering agents an any one of them could be the X in
Los Angeles, CA, USA
From: Keith Tapscott. on 25 Jul 2008 17:16
Richard Knoppow;743835 Wrote:
> I have somewhere a patent which I believe is for Microdol but will have
> to search for it.
> Richard Knoppow
> Los Angeles, CA, USA
What is the patent number?
I have seen some Kodak patents for fine-grain developers containing
sodium and ammonium chloride and a couple of patents for anti-stain
agents that reduce or eliminate dichroic fog.
From: Keith Tapscott. on 25 Jul 2008 17:26
Edgar Hyman`s Microdol substitute is 5 grams of Metol, 100 grams of
sodium sulphite, anhydrous and 30 grams of sodium chloride per litre of
stock solution although I don`t know how close that is to Kodak`s
Microdol-X or Ilford`s Perceptol or the exact additives to the
commercially sold products.
From: Richard Knoppow on 26 Jul 2008 13:05
"Keith Tapscott." <Keith.Tapscott..2d04e88(a)photobanter.com>
wrote in message
> Edgar Hyman`s Microdol substitute is 5 grams of Metol, 100
> grams of
> sodium sulphite, anhydrous and 30 grams of sodium chloride
> per litre of
> stock solution although I don`t know how close that is to
> Microdol-X or Ilford`s Perceptol or the exact additives to
> commercially sold products.
> Keith Tapscott.
One patent covering the Microdol type developer is:
USP 2466423 issued to John I. Crabtree and Richard Henn and
assigned to Kodak. The patent has some discussion of the
problem of silver fog in fine grain developers and suggests
some compounds for suppressing it. There are sample formulas
for both liquid concentrate and powdered developers. The
simplest is copied below but I suggest reading the patent
for a greater understanding of what the inventors were
trying to do.
Microdol _type_ developer
Water to make 1 liter
Metol 5.0 grams
Sodium sulfite, anhydrous 100.0 grams
Ethylene diamine sulfate 12.0 grams
Sodium metaborate 4.0 grams
Potassium bromide 0.25 grams
Sodium chloride 20.0 grams
The patent is dated 1945 so its about right for the
original Microdol. The X version was released a couple of
years later. Presumably the X indicates an improvment,
probably in the form of a better silver sequestering agent.
Kodak holds many patents on various sequestering agents,
only a couple are mentioned in the above patent.
Los Angeles, CA, USA