| Background:
Many
substances can develop silver-halide films, including cola drinks, tea,
coffee, red wine, human urine, and common kitchen and laundry materials.
They are not in regular use for many reasons, some of which are
obvious, but primarily because they are time-consuming, inefficient, and
typically yield high-fog, low-density, unpredictable results.
To develop films, these substances must
be mixed into water and the solution made alkaline. The alkalinity
activates the otherwise inactive developer. The degree of alkalinity
affects development speed and overall image contrast. Unfortunately,
most simple "kitchen cupboard" developers require strong,
caustic alkalis such as household lye or drain cleaner (both of which
are dangerous for children to handle), and they require
development times of about a half hour, sometimes much longer.
Characteristics:
Here we present a seemingly simple
formula that is actually quite sophisticated.
It combines two
non-toxic developers, coffee and vitamin C, each of which is a weak and
inefficient developer by itself, but which are
"super-additive" with each other. That means, when they are combined, the
combination is substantially
more active than the sum of its ingredients.
It uses a relatively common laundry ingredient, washing soda, which is a
mild alkali, as its activator.
This developer creates more
background density ("fog") than commercial developers.
However, the density is easily dealt with in printing or scanning, and
can be ignored.
Because it is non-toxic and does not use caustic alkalis, young children can safely experiment with it,
as long as they are careful to not drink it, since it would undoubtedly make them sick.
And keep it out of your eyes!
Instant coffee is preferred to brewed coffee only
because it is easier to use, and is more likely to be of uniform
strength from one batch to the next. There is no reason you couldn't
experiment with brewed coffee. Vitamin C crystals are preferred to
tablets, since tablets include inert binder that must be filtered out.
Citrus juice has too little ascorbic acid to be useful (one
cup of orange juice from concentrate contains only about 1/10 of a gram
of ascorbic acid).
Caution: this mixture has a revolting
burnt-coffee smell. It stains film brown, but the stain washes out
during the final wash step..
Recommendations:
This formula is presented with rough,
whole-number teaspoon measures, because it is not possible to know in advance the
potency and activity of ingredients sourced from a supermarket
shelf. You should probably experiment with varying amounts of
coffee. Keep the ratio of coffee to vitamin C at roughly 1:1 to 1:1.25,
by weight, or about 4:1 by volume.
You should definitely experiment with development times.
Shoot a roll of black and white film outdoors, with every frame showing
the same scene at the same exposure. In the dark, cut the roll into six
more or less equal strips, excluding the tongue. Develop one strip for,
say, fifteen minutes, and after it has been fixed, washed, and dried,
examine it. Wet film looks considerably different from dry film, so be
sure you examine it after it has dried. You should be able to guess
whether to develop the next strip for a longer or shorter time. After
you've developed and evaluated several, you should have a good idea of
the proper development time.
This formula should give you excellent, printable
images with just about any brand of instant coffee crystals. Play with it for a while, and be prepared to be amazed.
You may be interested in the original
Shutterbug Magazine article that provoked these experiments, which is
on-line at: http://www.photoglass.com/PHG/PVT/SBug.htm.
Please note:
The article implies that salt water can be used as a fixer. In fact,
fixing in anything other than thiosulfate is impractical.
Fortunately, sodium thiosulfate can be bought cheaply from pool supply
companies, who sell it as a chlorine reducer. Another resource, not
on-line unfortunately, is "That Last Cup of Coffee," page 35
of Darkroom
& Creative Camera Techniques, Sept/Oct 1995 issue.
|
| As you can see,
precise measurements of ingredients is not an issue. In
practical darkroom work, as opposed to scientific research, it is almost
always more
important to measure consistently from one batch to the next than it is
to measure out precisely what a formula calls for.
Add the
ingredients to the water in the order shown, dissolving each completely
before adding the next.
The washing soda may be perfumed, and it will
probably form a cloudy, somewhat gritty mixture that requires several
minutes of stirring. Neither matters. If it bothers you, filter it
through a coffee filter.
If the your solution fills with fine bubbles,
they should be allowed to dissipate before developing film.
This mixture retains its power to develop
film for at least 24 hours, even when exposed to air. However, to be
safe, you should probably only use it when it's relatively fresh. It
would be worthwhile experimenting to discover exactly how it changes
with age.
Processing:
Developing times vary according to the
film you use, and you should experiment with times between about 12 and
18 minutes. I like 15 minutes as a starting point. Agitate 30 seconds initially, then 10 seconds each minute
thereafter.
Stop bath: in the spirit of low-cost
photography, use a plain water rinse, at
least thirty seconds, with agitation. However, adding white household
vinegar or powdered citric acid to the water will neutralize the
developer more or less instantly, making consistent development easier
to achieve and preventing carry-over of developer into your fixer, which
will make your fixer last longer. Calculate the amount of vinegar or
citric acid to add so the stop bath contains about 1% acid.
Household vinegar is typically about 5% acetic acid, so use about five
times as much water as vinegar to get the proportions about right. Too
little acid is preferable to too much.
Fixer: Sodium thiosulfate crystals are
available from pool supply companies, or from many old-fashioned camera
stores. People with swimming pools use it to control excess
chlorine. Dissolve 24 oz (about 4 level teaspoons) of thiosulfate in 4 cups of water. This is a non-hardening
fixer and it may leave your film's emulsion prone to damage while wet,
so be careful how you handle the film. It will also not have as long a
working life as commercial fixers, which contain buffers and
preservatives.
Fix thin films (such as Bluefire Police)
for three minutes, and ordinary films for at least five minutes.
Wash for ten to thirty minutes or more in running
water. To conserve water, wash in consecutive baths of plain water,
agitating continuously for at least one or two minutes per bath. Click here
to read some information on this important step.
Shake off, or very gently blot
away, any water droplets that adhere to the film, being very careful to
not scratch the emulsion, which will probably be extremely delicate. Dry
the film hanging it in a dust-free place where
the air is still.
This is the only specialized
equipment you need:
Compact Developing tank
with two spiral reels,
light-tight lid for rotary agitation, liquid-tight lid for inversion or
rolling agitation, and instructions.
Chemical-resistant plastic. Process color or black and white film, 35mm,
126, 127, 120, 620, and 220.
ea.
|
