Argyrotype
by Mike Ware=20
(version of 12 August 1994)
A new 'user-friendly' iron-based silver printing process, related=
to the
Kallitype, Argentotype, Sepia, Brownprint and Van Dyke processes=
of the
19th Century, but offering some advantages over them in the economy=
of
materials and effort, and in the quality and permanence of the image.
Sensitizer Chemicals needed:=20
Sulphamic acid 7 g (spelt 'sulfamic' in the USA)
Silver(I) Oxide 7 g
Ammonium Iron(III) Citrate (green crystals) 22 g
Tween 20 (wetting agent) 0.2 cc
Distilled water to make 100 cc
Making up Sensitizer (under tungsten light):
1) Heat about 70 cc of distilled water to 50-60=B0C, and dissolve=
7 g of
Sulphamic Acid in it.
2) Add 7 g of powdered Silver(I) Oxide to the hot solution 1)=
in small
amounts with vigorous stirring until all is dissolved.
3) Add 22 g of Ammonium Iron(III) Citrate (the green variety)=
to the
warm solution in portions, with stirring, until it is all dissolved.=
Allow
to cool.
4) Add 0.2 cc of Tween 20 and mix well.
N.B.The appropriate quantity of this wetting agent is variable=
and
will depend on the paper used. It may be added separately.
5) Add distilled water (at room temperature) to make a final=
volume of
100 cc and filter the solution to remove any small amount of solid
remaining.(The solution should be a clear deep olive-green colour.)
6) Store in a brown bottle in the dark at room temperature.(The
solution should keep well, for a year at least. If it throws down=
a small
amount of black precipitate, it can be re-filtered.)
7) To make a more contrasty sensitizer, dissolve an extra 1=
g of
sulphamic acid in 100 cc of the sensitizer.
CAUTION The solution is toxic and will stain skin and fabrics: wash=
away
spillages with plenty of cold water.
Papers
The purity of the paper is *critical*: it should be a 100% cotton=
cellulose
paper, internally sized with "Aquapel" or its equivalent. Of those=
(UK
papers) tested so far, Whatman Watercolour, Saunders Somerset and=
Atlantis
Silversafe Photostore are recommended, but the best is Ruscombe Mill's
handmade Buxton paper. I cannot answer for US papers - experiment=
is
necessary.=20
The wetting agent, Tween 20, is included in the sensitizer formulation=
to
assist uptake of the sensitizer by the cellulose fibres, which minimises
"bleeding" of the colloidal metal image during wet processing, but=
it may
cause uneven penetration of some papers which have a mixture of fibres=
in
the furnish.
Coating
A 10"x8" coat requires about 1.6 cc, depending on the paper, if a=
glass rod
spreader is used. Brush coating will consume more.
Allow a few minutes for the sensitizer to soak in, until the paper=
surface
appears non-reflective, then dry for about 10 minutes in a stream=
of warm
(40=B0C) air. Alternatively, simply allow to dry at room temperature=
and
humidity for about an hour. The sensitized paper should be used within=
a
few hours, unless a desiccated box is used for longer term storage:=
'shelf
life' in a dry environment should be at least a week.
Negatives
As with platinum-palladium printing, a negative with a long density=
range
(0.2 to 2, or so) is desirable, obtained by "overdeveloping" by 70%-80%.
Softer negatives may be accommodated by using the more contrasty=
sensitizer
recipe. [Indeed, by mixing the two formulations, the contrast of=
this
sensitizer could be 'fine-tuned', though I haven't tested this.]
Printing
Printing is by contact, using a UVA source or the sun. Exposure is=
similar
to other iron-based processes, e.g. platinum/palladium.
If the relative humidity of the paper is 'normal' (ambient RH between=
40
and 80%), a detailed print-out image will be obtained, orange-brown=
on a
yellow background, which gives a good indication of correct exposure,
making test strips unnecessary. A little development (half to one=
stop) can
subsequently be expected to occur in the high values during wet processing,
and there will be considerable 'dry-down' of the tonality: both factors
should be taken into account in judging exposure; the colour will=
also
darken to a rich brown in the fixer bath. It is better to overexpose=
than
underexpose, because a dense image can be 'reduced'.
Colour
The colour of the print-out image may be modified to a more neutral=
tone if
the sensitized paper is humidified before exposure by leaving it=
above
water (100% RH) for 30 minutes at room temperature. This is a very
economical method of colour control!
CAUTION: Humidified sensitized paper can damage negatives during=
contact
printing unless a protective layer of very thin polyester film is
interposed between the two.
Wet Processing
This is extremely simple and non-critical, requiring only one inexpensive
solution, 2% Sodium Thiosulphate:
dissolve about 20 g of the crystals in 1 litre of water.
This bath has a capacity of about ten 10"x8" prints and should be=
replaced
when necessary.
1) Develop and clear initially in running water at room temperature=
for 5 mins.
2) Immerse in the 2% Sodium Thiosulphate clearing bath for about=
3 mins.
3) Wash the print in water for 20 mins and air dry at room temperature.
NOTES:-
1) The yellow unexposed sensitizer should disappear completely within=
this
time. If there is any "bleeding" of colloidal silver metal, indicated=
by a
red-brown stain running off the image and loss of image density,=
then this
problem results from the paper fibres failing to trap the tiny silver
particles; it is especially likely if insufficient Tween is used.=
The
effects of "bleeding" may be minimised by processing the print face=
down,
to avoid staining adjacent areas.
If a particularly long tonal range is desired with very delicate=
high value
gradations, the exposed print should be left in a humid atmosphere=
(100%
RH) for ten minutes before wet processing; several steps of highlight
detail will build up.
2) The image should intensify in the fixer, improving the shadow=
gradation,
and the colour will rapidly transform from red to brown. (As the=
bath
'ages' its action in this respect increases). Overlong treatment=
in this
bath and exposure to air will result in loss of image density especially=
in
the highlights; it may be used to "reduce" an overexposed print,=
or a
standard, non-acid fixer may be used. If, on the other hand, very=
delicate
highlight detail is desired, a little ammonia may be added to the=
clearing
bath to make it distinctly alkaline (pH 9-10); this inhibits the
dissolution of silver, but may raise the level of residual iron in=
the
image.
3) The image 'dries down' significantly - at least one Zone. Heat=
drying on
a ferrotype plate or by ironing, may shift the colour to a more neutral
blackish brown.
Permanence
Like any colloidal silver image, an Argyrotype is inevitably rather
susceptible to attack, especially by acids and sulphur-containing
substances. However the residual iron and silver in the unexposed=
areas
should be very low and image stability and lightfastness are good.
If improved permanence is desired, then try selenium toning (Kodak=
selenium
toner, diluted 50 or 100 times for a minute or so). Toning with gold,
platinum or palladium should also be possible, and the image may=
also
respond to sulphide toners, but I have not yet tested all these options.=
I
would welcome hearing of your experiences.
Disclaimer
This information may be copied and circulated freely (preferably=
with
acknowledgement!), but the author cannot accept liability for any=
injury,
damage or loss resulting from its use.
Reference (which provides some of the chemical rationale to the process)
'The Argyrotype Process' by Mike Ware, British Journal of Photography,=
13
June 1991, pp17-19.
=46ootnote: I believe there may be difficulty in obtaining silver(I)=
oxide in
some parts of the world. If so, I could post a simple means of preparing=
it
from silver nitrate.
Good wishes
Mike
=20