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From: Gene Alan Townsend <wings@primenet.com>
Newsgroups: rec.photo.equipment.large-format
Subject: Direct Carbon Prints
Date: 25 May 1997 13:04:00 -0700
Here is an outline for a printing process I've used over the years that
I've never shared with others. This technique produces carbon prints on
glass substrate directly without using any difficult transfers. It is
simple and inexpensive to perform, but require the direct sun for
exposure. Glass is breakable, but chemically clean and archival, unless
of course it is broken. :-)
All excellent photographs are covered with glass anyway. The carbon
print is on the back side of the glass, the glass index matching the
print to the glass surface, resulting in lack of second reflection and
enhancing the appearance of a well done print. Behind that is applied a
white ground, using tempera or permanent oil paints, or other pastel
colors of choice, allowing simple hand-tinting using opaque materials,
easier to apply than transparant oils over a print surface.
Advantages:
1. Very inexpensive, simple process.
2. Very flexable. Any pigment color can be used to provide the dark
tones, any pastel the ground.
3. Easily hand-tinted.
4. Archival beyond reproach.
The materials are the same as for any carbon process.
1. Glass plate, preferably single strength, which will give sharper
images, is meticulously cleaned on one side. I prefer ground pumice and
isopropyl alcohol for this, using a cotton ball in circular motion.
2. Plate is carefully leveled, and slightly warmed by placing light
bulb over it for a few minutes.
3. Sensitizer is mixed using about 5% gelatin, 1 to 3% potassium or
ammonium dichromate, and an appropriate amount of ground pigment
according to taste. Lamp black gives pefectly neutral tones. Add the
gelatin to water, and allow to swell a few minutes before heating. I
like to use empty 35mm black plastic film cans for this, mixing about
100 cc's at a time. Warm the gelatin solution by placing in pan of
water, and slowly heating on stove until molten. Do not overheat. Add
the dichromate and pigment powder in subdued light, mixing by gentle
rocking to avoid air bubbles.
4. Use a small funnel and some filter paper to apply the gelatin. Wet
the filter paper with hot water, and place folded in the funnel.
5. Pour the gelatin solution into the funnel carefully, over the glass
plate, applied in a line down the middle of the plate. This reduces
bubbles and undisolved particles, both of which will create large voids.
6. Using a large, clean comb, spread the solution evenly over the plate
by pushing back and forth slowly. Allow to gel and dry over night.
7. Expose to negative placed on uncoated side of glass plate. Place
second glass over the negative to sandwich neg.
8. Exposure must be done in a deep box, about twice as deep as the
longest side of the print area, and just slightly larger in opening than
the print. Direct sunlight must be used, and the boxed moved to track
the sun. In southern Arizona, my exposure times run about 10 minutes
using black pigment.
9. Process in a warm water bath by placing glass emulsion side up in a
tray, and carefully adding warm (approx. 100 deg. F) water, rocking tray
gently for a few minutes until the image has correct density. Using a
white colored try will help in determining this.
10. Harden gelatin in standard hardening solution. Alum works best for
me.
You will need to experiment with the pigment concentration for this
process. Most art supply stores will have a selecion of permanent dry
pigments, as mixing oil paints has become popular in recent years.
11. After dry, apply the ground using white, or other light pastel
colored, tempera paints to the bacside of the gelatin. Oil paints can
also be used, but take longer to dry. Selectively coloring is easy
using various colors here.
12. Easiest mounting is to frame with foam tubing used for insulating
1/2 in dia. pipe. This foam is black, and is slit full length, and can
be pushed easily onto the edge of the glass.
Have Fun
Gene A. Townsend
>>>
Cor Breukel
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"The Infrared Gallery"
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