sodium
in general has taken over my life. sodium sulfite being the obvious
guilty party in my darkroom, and sodium chloride being added
everywhere in my food. i really don't like the taste of salt, and i
restrain from smelling, or inhaling fumes, of sodium sulfite.
in any case, sodium sulfite is everywhere in silver printing. no
really: everywhere. from beginning to end - it even used to be a
preservative in food. so this problem of oxidation made me
think of how sometimes, when i look at a print, i see a list of
chemicals necessary to the process. a long list, mind you. let's
try to look at what goes where in silver photography: the magic of
the image appearing in the developer is actually quite complicated,
yet fascinating. and many of these chemicals can be quite harmful, to
both people and the environment. the process is not to be taken
lightly. osha recommends to just "water down" your
chemicals into the drain, with enough water so it doesn't damage the
pipes in the building. yep, that's an actual quote.
and
i will not mention the several gases released from mixing powder, or
by contamination. i have always known all this, my dad was an
engineer and mathematician, an uncle a chemistry professor, and
another worked in optics -kind of like oliver sack's "uncle
tungsten" - i walk into my darkroom with a certain knowledge of
chemistry, i understand where harm can come from, and a side effect
is that the skin on my hands is very dry. can't really put cream on
your hands to touch film and photo paper, it's chemically harmless,
but visually awful.
anyway:
sodium sulfite, sodium erythrobate, sodium metabisulfate, disodium
tetraborate pentahydrate, pentasodium ethylenenitrilo tetraacetate,
hydroxymethyl, phénitpyrazolidin. that is just a taste of x-tol. no
hydroquinone you'll notice. and it's a great name, extol the virtues
of this developer! but we forgot that film itself has to be
manufactured first. acetate, i don't feel like going into details
here, just acetate, and gelatin… well, again, let’s just
call it gelatin and concentrate on what gets mixed in with it, namely
crystals. and how does one get these crystals? bars of
silver are dissolved in nitric acid to form silver nitrate, and
combined with bromide as an alkali salt, potassium bromide for
example. this results in light sensitive silver halides
crystals. mixed with gelatin it makes an emulsion, a silver
halides emulsion. voilà.
why
gelatin? it’s transparent, grainless, it’s a liquid when heated
and gels when dry, yet it swells enough when in contact with liquid
chemicals to affect halide crystals.
anyway,
so you mix a solution of silver nitrate with a halide -any alkali
metal halide- say, sodium bromide -don’t forget the ammonium
hydroxide, ammonium bromide, thymol and alcohol. the emulsion
maker may control the very size of these crystals and mix them over
several layers. the crystals get heated, ripening as it is
called, they dissolve and crystallize again. remember, within
each crystal, the atoms are electrically charged (ions) and placed in
a grid of sort by electrical attraction, with free-to-move silver
ions, as well as important -to the latent image, and overall
exposure- crystal imperfections.
so
the film gets exposed -insert entire history of photography here-
the silver ions interact with negative charges, a latent image forms,
the bromide ions are neutralized to atoms, then absorbed by the
gelatin. next thing you know, you’re gently agitating at
equal intervals… the tiny silver deposits will be grown and
amplified (a lot) to give a visible image. the hydroquinone -or
metol, or phenidone- and supportive agents including an alkali and a
preservative start the process. as you agitate the tank,
electrons go for the exposed silver halides carrying silver atoms.
the developer gets full of potassium bromide and other chemicals
without electrons. developing time is over, everything gets
rinsed in water and goes down the drain. let’s skip over the
temperature if you don’t mind… also, you may decide the see
the whole process with infrared, or a green light, and develop by
inspection for even more control.
then
it all needs to be fixed, made stable. ammonium thiosulfate,
boric acid, acidic acid, and again, sodium sulfite. residual
processing chemicals contain sulfur compound and will deteriorate the
image if not washed properly. ironically, a small amount of
residual thiosulfate is needed against oxidizing agents. all
the unexposed, invisible silver halides get washed away in the hypo
(fix). you can then recover the unused silver by electrolysis.
and
don't worry: whatever grain structure is inherent in a film emulsion
will be retained in the developed negative. do we even have to
mention the energy of electrons, the speed of photons needed to get
those latent silver atom specks? crystals are about 1 micron in
diameter and contain about 10¹² silver atoms (or grains). you
need an electron microscope to see these grains. my grain focuser
only sees what we commonly call film grain, but is just really clumps
of about 40 actual grains. long story short, we have a negative to
print, more chemicals to gather and mix.
dihydroxy
benzene, sodium carbonate monohydrate, hydroquinone and potassium
bromide. the thing is that dektol makes my skin dry. perhaps then a
mixture of sodium sulfite, sodium carbonate and hydroquinone, lpd
powder developer seems to be better for me in the long run.
what
type of wood was used to make the base of the paper? for our purpose
perhaps it's best to just talk about the emulsion. although that was
a concern of mine when ilford went from multi IV to the classic fiber
paper. everything matters, any change at all changes things, not
everything necessarily, but enough to make a difference. and yes, it
is now a different wood being used for ilford papers. change is
difficult in a field where consistency is a factor, but necessary in
a technology-based environment. more layers of halides, all equally
sensitive to blue on variable contrast paper, yet each differently
sensitive to green. the halides are now being bombarded with yellow
and magenta light. bam. negative film illuminated onto negative
paper, silver halides into silver metal, reduction from salt to
metal. and then it gets dipped in developer, the silver halides
particles become metallic silver. stop. acidic acid. stop. sodium
thiosulfate removes all untouched silver halides by turning it into a
water soluble complex. wash with plenty of water, drain with plenty
of water. the water is on all day. water water water.
and
ventilation. plenty of ventilation.
all
this solid state chemistry moved indoors before electricity mind you.
velox emulsions are 500 times faster than albumen.
photography was almost a hundred years old before an enlarger with a
light bulb was brought into a darkroom as a regular practice. we are
now way past the gaslight papers era, and exposed our perfectly
evenly coated emulsion with a lightbulb (well, several halogens
etc.). yes, you read right: gaslight paper. i'm glad i have
electricity and mostly mixed chemical formulas where i just add
water. it's very manageable for the everyday. i think twice before
any exposure, i don't waste paper, i take the first guess very
seriously, it's better for the environment.