Marek and All,
Did you see this which I posted to the List in May 2006 ? For those
who have any interest here it is again.
Using Javel Water instead of the 115 F soak before spray
development looks very much like the ''Arvel '' process.
Also you may note that sensitization is by immersion
and not by the pre- mixing of the Amm. Dich with the gum coating.
This would mean that unsensitized paper could have been
produced by the Fressons, which they did, whereas presensitized paper would have
presented problems with dark effect.
John - Photographist - London - UK
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From ''Photography: Theory and Practice''
by L.P.Clerc, Hon.F.R.P.S. Pub. 1954 (3rd edition)
Edited by A. Kraszna - Krausz
BICHROMATED WASH -
DRAWING
''This interesting variation of the
gum-bichromate process is particularly suitable for obtaining large
pictures, by printing under large negatives.
A drawing - paper is first sized
with a very thin film of weak gelatine solution. The beginner should choose a
paper with fine grain. For this the following mixture is used
-
Crystalized
sugar
4g
Soft photographic
gelatine 4g
Water 100
ml
prepared by allowing the gelatine to swell in the sugar solution, and dispersing
it over a water bath below 115 F. The sizing is preferably done in a room
at a temperature of at least 70 F; the paper should then be at the same
temperature as that of the room. It is fixed with drawing pins to a
drawing - board, placed level and the gelatine solution poured on the centre in
the proportion of 1 ml for every
16 squ '' of surface to be covered.
The solution is spread with a swallow - tail brush, previously impregnated with
the gelatine solution, and squeezed out in its edges. The solution is driven
onto the pores of the paper by vigorous operation of the brush, spreading
it evenly until the sizing has a mat appearance. The sheet is then passed
through the steam from a pan of boiling water until the gelatine becomes
uniformly glossy. In the interval between the two sizings the brush is
held in the steam to prevent the gelatine in it from
setting.
Now, put 1 g of degreased lamp black (
choose a black of brownish tint ) on a piece of glass placing the powder in the
form of a crater. Then pour into this 2.5 ml of a 50% solution of gum
arabic; mix thoroughly with a flexible knife, adding gradually 2 ml of
water. Grind with a glass muller for about 10 minutes, until the mixture
becomes perfectly even. To cover a sheet of paper 20'' X 16'' about
2 g of this paste is placed in a clean cup, and about 0.75'' of the strip
delivered by a tube of sepia water colour is added. This gives a warmer
tone, and at the same time, improves the adhesion of the coating. Now add
from 15 to 18 ml ( the smaller quantity in cold and damp weather, the larger in
warm and dry weather ) of the following mixture prepared with boiling water
-
Crystallized
sugar
2 g
Starch
2 g
Water
100 ml
After
mixing thoroughly, this paste is placed at the centre of the gelatine coated
sheet and spread with the swallow-tail brush previously charged with
water. When the colour begins to thicken, a flat goat- hair brush is used
to finish off the coating, the first stroke of this brush being at right
angles to the last stroke of the swallow - tail brush, so as to break up the
streaks. Continue in this way until the sheet is surface - dry, and
then leave to dry thoroughly by hanging from stretched
cords.
The sensitizing is done, as required, by immersion in a 1% solution of
ammonium bichromate, with the addition of 1% of neutral sodium or potassium
citrate.
The negatives best suited for this method of printing have a density range of
about 1.3.
The exposure should be equal to that required to make a P.O.P print for toning
and fixing.
Before development, the print is immersed face downwards for about ten minutes
in a dish of water at
115 F, taking care to avoid adhering
air bubbles. As the water slowly cools down, the print is moved about from
time to time. The print is then fixed to a rigid support, sloped to about
the angle of a painter's easel, and development is begun by squirting the
surface with water at a temperature of about 18 F above that of the soaking
water. This may be done with a toilet spray or an air brush. The
spray is held from 12'' to 16'' from the print, and the water is squirted
all over the surface. The development may be localized as required by
bringing the vaporizer nearer. Development takes about 20 minutes for a
surface 9'' X 5'' which has been correctly
exposed. ''
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