Microdol was a re-used Kodak trade mark. The first was Microdol and
then Microdol-X. I think the X or later version had an anti-silvering
agent in it to suppress dichroic fog. Ilford Perceptol is, as far as I
can tell, identical to Microdol-X, which I believe was discontinued some
time ago. One of the main fine grain agents in both is sodium chloride,
i.e. table salt.
Both have a fine grain property when used full strength but loose
it when diluted. There is a loss of about 3/4 stop of speed when used
full strength. Both become high acutance developers when diluted one
part stock to two parts water. There is no speed loss when diluted.
Films like 100T-Max have very nearly the same fineness of grain as
Technical Pan when developed in Perceptol full strength but at a speed
of around ISO-50 and without the contrast control problem.
Varigam was a variable contrast paper made by Defender and later
DuPont/Defender. I think it either the first V.C. paper or at least the
first on the U.S. Market. The original Varigam had a different emulsion
arrangement than later variable contrast papers so needed a different
set of filters. I think the original Varigam may have come with just two
filters, High and Low contrast, so that mid grades were printed by
successive exposures of the required times.
When used without filters the contrast of variable contrast papers
is about "normal" or grade-2 but it depends on the spectral quality of
the light source.
If you bought graded paper it was not Varigam. Varigam was a very
great convenience if you had to print negatives from various sources.
Virtually every manufacturer of film or paper had a formulary of
their pet formulas to which one must add formulas published by the
chemical suppliers.
Probably the most reliable formulas were those published by Kodak
but there were many interesting ones published by Ansco and its
predecessor AGFA. AGFA, a chemical company, produced vast amounts of
potassium salts as by products of other things and tended to use the
rather than sodium salts in their photographic formulae. Some users
think there is a difference in the look of prints developed in
developers containing potassium but I have yet to see a convincing
demonstration. Metol, the frequently specified developing agent, was
actually an AGFA trade-name, Kodak sold the same stuff as Elon. Defender
(later Dupont-Defender) had some unique formulas. I used to use Defender
paper developer, probably because it was marginally cheaper than Kodak
Dektol.
For years I collected photographic literature. Much of it is in
storage now but I still have a good selection of material on compounding
developers.
Despite the range of formulas I would still work with packaged
stuff from Kodak or Ilford.
You need perhaps a dozen chemicals to compound a wide variety of
black and white processing formulas. Some are expensive and somewhat
difficult to obtain now but you can still get Pyro and Amidol. I used
Amidol paper developer at one time, long ago, because it supposedly gave
very deep blacks. Amidol is good developer but has no tray life and must
be mixed fresh each time its used. It also produces extremely persistent
stains if it dries on anything. Pyro developers were the standard until
about the mid 1930s when they were displaced by Metol-Hydroquinon
developers for both film and paper. Pyro also has a short shelf and tank
life but some formulas were devised, mainly for motion picture negative
development, with less vulnerability to oxidation. Also, pyro can
produce a stain image that increases effective density when used for
printing on blue sensitive material. In fact, there are many
non-staining pyro formulas devised for motion picture processing where
it was not desired. The "standard" three part A-B-C Pyro formula was
published in identical form by at least Kodak, AGFA/Ansco, Defender, and
others. The three parts are formulated to extend the storage life but
tray or tank life is still very short (hours).
I always found mixing my own to be interesting and I like to
experiment but for serious work give me the packaged formulas every time.
On 9/12/2017 8:36 PM, Don Williams wrote:
At 05:54 PM 9/12/2017, Dick K. wrote, in part:
If the contrast is reduced by reducing development, the exposure index will decrease by about a stop for a one paper grade decrease in contrast. In fact, the ISO standard includes a chart showing approximate correction for speed vs contrast.
Reminded me of a couple of things.
I remember, I think, Microdol . . . a fine grain developer. I sort of think it did result in slightly lower effective film speed but finer grain. In that line, I think you could buy various developer components to make custom mixes.
I also remember Varigam(?) print paper. I looked that up just now and there are many similar papers, still for sale. So many brands and such a price range. I had am Omega B-22 but don't remember ever buying Varigam filters - I just bought various paper "grades".
DAW~
