Hi All and Chris,
For those who missed it or lost it , could this be considered to be
a gum process ?
Wonder if anyone on this list has tried it?
John - Photographist - London - UK
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
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
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
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
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. ''