I don't think there is anything original in this, but equally I can't tell
you where the ideas came from. It is a few years since I actually did this,
and my notes are a model of obscurity, so I hope I don't forget anything
vital.
You need a sheet of glass a few inches wider than the sheets of carbon
tissue you want to make, and a solid metal bar longer than the width of the
glass - I used a thick aluminium ruler (about 50mm by 10mm section). 1.5mm
thick plastic strips are fixed to this with tape to raise it above the
surface of the glass sheet when you pull it across. These slide along strips
of masking tape at the edge of the glass
Add 70 g Croda limed ossein 260 Bloom gelatin to 625 ml water and keep warm
(not hot - from memory about 45 degrees Celsius) using a double boiler until
it dissolves. Add 30g white sugar and dissolve this, then filter through a
nylon filter (ensures there are no lumps left undissolved.)
Add 23ml Rotring Black drawing ink, and mix well, maintaining it around 40
degrees.
Level a large glass sheet using plasticine under it (check with spirit
level). Put a couple of strips of masking tape along the two longer edges -
two layers of tape thick. Warm the metal rod by submerging it in a bath of
hot water for several minutes.
Use cheap absorbent paper such as lining paper from a hardware shop. Soak
in hot water, lift and drain carefully (it isn't very strong when wet) and
place on the glass sheet, using very gentle pressure with a squeegee to
flatten it.
Rapidly pour on the correct amount of the mixture and allow to spread out
(about 80ml per square foot). Put the warm metal blade in position and move
it across the paper and back to get a level coating. (A palette knife can be
used to return some of the excess gelatin that sticks on it to the pan.)
Allow to set before peeling carefully from the glass and leaving (face up
of course!) on sheets of newsprint on a flat surface to dry for a few hours.
It will curl, but this doesn't seem to matter. You may find you need to
adjust the coating thickness (more or less tape or thinner/thicker plastic)
to get the results you need.
This is a pretty messy business. I could only do it at home by persuading my
wife to go and visit her mother for a few days.
I suspect other gelatin might work as well. I used the Croda because I had a
large free sample.
Peter Marshall
Family Album/Gay Pride - http://www.dragonfire.net/~gallery/index.html
Also on Fixing Shadows: ----------- http://fermi.clas.virginia.edu/~ds8s
Future Press and elsewhere... E-Mail: petermarshall@cix.compulink.co.uk