Suitable Papers
In principle all papers meant for platinum print are
suitable as well as strongly coated water colour paper. Preferably I use
thin ( 90 g) coated water colour paper by Fabriano, heavy water colour
paper by Strathmore, and Arches paper for platinium print.
I tried Rives BFK as well but it had to be additionally
sized with gelatine or starch in order to get an even coating.
A silver nitrate solution is thinner and faster to be
absorbed by the paper, in contrast to the sensitizing solution used for
platinum print. It is also colourless which makes it more difficult to
see which places you have coated already.
Basic Formula for Salted papers
For both the solutions you just need a few, inexpensive
chemicals.
The first solution consists of:
Water 1000 ml
Gelatine 8 g
Sodium citrate 22 g
Ammonium chloride 22 g
Both sodium citrate and ammonium chloride are salts. Gelatine
serves as additional glue; it can be substituted by starch. Gelatine produces
a cooler tone, starch a warmer one.
The second solution:
Destilled water ( 42° C) 60 ml
Siver nitrate 8 g
This is the sensitizing solution which makes the paper
photosensitive. Silver nitrate is a rather expensive component yet still
far cheaper than platinum or palladium.
Preparation of the Salt Solution:
We use half the water to soak the gelatine for 10-20
minutes. Common household gelatine will do the job nicely ( will be totally
adequate ).We heat the remaining water up to 42° C and in it we dissolve
the sodium citrate and the ammonium chloride. After the gelatine has soaked
sufficiently we put the two together. If we want
to use starch we use the same amount of liquid and substitute 4 g of gelatine
by 10 g of starch. Again, ordinary household starch will do. First
we dissolve the starch in a little water, bring the rest of the water to
the boil, add it to the starch and boil the mixture for 3 minutes. Then
we add the salts.
If you find the boiling procedure too cumbersome you
can use bottled spraying starch which works just as well.
The Salting of the Paper:
First we soak the paper in the salt solution either by
brushing it heavily or by sliding each sheet into a bowl with the solution
and leaving it there to soak for 30 seconds. I personally prefer the latter
method. There the whole surface will be in contact with the salt solution
whereas you may leave out spots when you just brush the paper with this
clear liquid.
You can dry the papers by hanging them up on a line or-
if you are in a hurry- by using a hairdryer.
I don’t keep any leftover salt solution for more than
a few days but rather have a stock of salted papers because those you can
keep indefinetely. The solution will disintegrate quickly and form jelly
lumps.
Sensitization:
We need destilled water for the sensitizing solution.
There are always chlorides and other substances in ordinary tap water which
would otherwise react to the silver nitrate. We warm the destilled water
in a double-boiler up to a temperature of 42°C and dissolve the silver
nitrate in it. | As a solution it is not yet photosensitive. I keep it in
a dark brown bottle you can drip.
The amount of sensitizing lotion needed per sheet depends
on the amount of glue used on the paper. With a soft pencil we mark the
picture size and quickly and evenly distribute the silver nitrate
solution. For a print size 8x10“on Arches paper for platinum print we need
35 drops if we work quickly and skillfully.
For good reasons some photographers like to use the trough
method.
You fold the paper in shape of a flat trough, the area
for the picture being its bottom. You then pour into it an ample amount
of silver nitrate solution, swirl the inside of the trough and let the
rest run back into the bottle.
In the examples shown I used an acrylic pole with a handle
for sensitization. The pole has to be quite straight and - depending on
the format of the paper- about 12 to 20 cm long. If then you apply the
solution without pressure the coating will be much smoother than with a
brush.
This work is much more delicate than the preparation for platinum print
for the silver nitrate as well as the salt solution are both colourless
and will also be absorbed much faster.
The drying of the paper in a dark room takes about 10
minutes. It is faster with a hairdryer but only with cold air for heat
would alter the sensitivity as well as the contrast.
After drying we can sensitize for a second time. The
richer in silver the paper the deeper will be the tone and the contrast.
Under very dry conditions the sensitized and dried papers
will keep for a few days, in normal humidity they could be slightly darkened
even overnight. For a longer period they will keep well if you freeze them
in a tightly closed container, adding a chemical like Silikagel to keep
them dry.- Finally a good advice: wear an apron and rubber gloves when
sensitizing because the silver nitrate will stain anything it touches.
Rinse it off your skin straight away with a lot of water. On clothes the
stains will be dark brown at first, then black, and will take about a week
to disappear. You will find a recipe against silver nitrate stains below.
Print-out papers will be exposed by the sun or a strong
artificial UV-source. The procedure is the same with the exposure of POP
platinum prints.
By exposure we can also influence the contrast to a certain
extent. The more UV rays there are the more contrast you get. If you place
the contact exposure frame directly into the sunlight you will get slightly
softer prints than in the shade.
Watering- Fixing - Watering:
After exposure we water the printed picture in a bowl
under running water until the water is running clear. The milky colour
is a sign for superfluous unexposed silver nitrate. Too much watering will
result in a thinner picture.
The watering is followed by an ordinary, not hardening,
fixing bath. Afterwards you water the print as you do with any silvergelatine
picture. Hang it up to dry or place it on a net. Finished.
Toning:
The variations from a deep brown to light shades of red
and between cooler and warmer tones are due to the choice of paper, the
difference between glueing with gelatine or starch, and how many layers
of senzitizing solution were applied.
You can get further tone variations by toning - e.g.
gold toning. |
Recipe against silver nitrate stains
Kodak TC 3:
Solution A:
Water about 750 ml
Potassium permanganate 2 g
Concentrated sulphuric acid 4 ml
The whole mixture should be 1000ml.
NEVER pour the water into the acid! Always the other
way around.
Keep solution in a dark place.
Solution B:
Water about 750 ml
Sodium bisulfite anhyd. 30 g
Sodium sulfite anhyd. 30 g
Add sufficient water to make up to 1000 ml.
Silver nitrate stains on your fingers:
Pour solution A in a bowl, put your fingers in it, rub
if neccessary.
Rinse thoroughly.
Then bathe your fingers in the same amount of solution B.
Again, rinse thoroughly.
Use handcream afterwards.
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Cameras
Alternative Printing
Salted paper kit