[LargeFormat] Old Time Printer...Antique Roadshow...

[Richard Knoppow]

----- Original Message ----- 
From: "tripspud" <tripspud@transbay.net>
To: <largeformat@f32.net>
Sent: Wednesday, November 05, 2003 11:41 PM
Subject: Re: [LargeFormat] Old Time Printer...Antique
Roadshow...


> Hi Les!
>
>       I don't think this one is good for alternative
processes.
> I was on the alt e-mail list for awhile.  But it was all
> platinum and gum.  I was interested in silk screening
> with photographs.  I've seen some stunning work in
> color with quite a bit of fine detail, not like Warhol.
>
>      I had an aristo box when I attempted and
> failed with Carbro printing.  These are great
> for most alternative printing.
>
>
> Cheers,
>
> Rich Lahrson
> Berkeley, California
> tripspud@transbay.net
>

   I think what you must have tried was carbon printing.
Carbro is similar, but not the same. Carbon is one of many
processes that depends on differential hardening of gelatin
sensitized with bichromate where it is exposed to light. It
takes a very intense light to "expose" the carbon "tissue".
The light is on the order of what is necessary for printing
out paper, overcast sunlight or a "plate burner" is
generally used. Like P.O.P. it is a contact printing
process.
  Carbro, short for Carbon-Bromide uses the same sort of
bichromate sensitized gelatin "tissue" but it is "exposed"
by squeegeeing a silver-gelatin print into contact with it
and leaving it for a time. The dichromate bleaches out the
silver image on the print and in the process the gelatin
becomes hardened where the image is. The print can be
redeveoped and used again.
  Carbon tissue is "developed" by treating it with hot
water. This dissolves the un-hardened gelatin, leaving a
relief image in gelatin. The gelatin is then transferred
onto a final paper support.
   This is actually similar to the processes used for making
other kinds of prints such as oil, the counterpart of which
is bromoil.
   In a carbon print the gelatin is used directly to make
the final print. The gelatin "tissue" is colored with a
pigment, typically something similar to water colors are
used in the making of the tissue. Because the image is made
up of pigment rathere than dye it is possible to make it
very light fast. While the gelatin itself has some
vulnerabilities a carbon print is at least as permenant is a
toned silver-gelatin print, probably more so.
   The carbon-bromide, or carbro, process allows
enlargements from small negatives to be made relatively
easily. One simply makes a suitable enlargment on regular
enlarging paper (the bromide part of the name).
   In the past, when the carbro process was in common use,
special silver-gelatin papers were made for it. These
differed from standard printing paper mostly in not having a
gelatin overcoating. In order for the process to work the
dichromate from the carbon tissue must diffuse through the
overcoating of the enlarging paper. It will do this but the
overcoating slows down the process and tends to make edges
slightly blurred from the lateral diffusion of the
chemicals.
   For many years, at least during the 1930's through the
early 1950's, three- or four- color carbro prints were used
as the originals for high quality four color advertising
illustration. The three colored tissues were rolled into
register with each other. Sometimes a forth black "key" was
used as in four color ink on paper printing.
   The color carbro process is very difficult and time
consuming. Practically refrigerated workroom is needed. Most
of the labs specializing in this process were in New York
and specialized in servicing the advertising business. The
original negatives were made by color separation cameras of
one sort or another.
   Color carbro prints began to be challenged by the Kodak
Dye Transfer process in the mid 1940s when an improved
version became available. Kodak had for years offered an
earlier version, called the Eastman Wash Off Relief Process,
but it had too many problems and didn't catch on. The later
version drove out color carbon fairly quickly. It was easier
and the prints were sharper and easier to retouch and
modifiy.
  Another nail in the carbro coffin was Kodachrome. Sheet
Kodachrome became available around 1939. It could be
retouched directly and color separation printing plates
could be made directly from the transparencies. The
resulting illustrations were both more saturated and sharper
than those made by re-photographing color carbro or even dye
transfer prints. Dye Transfer, however, continued to be
popular for proofing or use as an original. An examination
of high quality magazine printing from, say, the mid 1930's
to the mid 1940's will indicate the very noticable change in
the quality of color illustrations.
  Because Kodachrome sheet film had to be processed by Kodak
in Rochester the use of three-color "one-shot" separation
cameras continued until the release of Ektachrome and
Ektacolor, which could be processed by the user, or at least
a private lab, in the late 1940's.
  While the Autocolor company of London was famous for its
carbon tissue the advertising community found it to be
lacking in quality and reliability so most of the tissues
used by it were made by the manufacturers of three-color
cameras, Thomas Curtis, on the West coast and National
Photocolor (who absorbed Devin) on the East coast.
   I think there is a fellow currently making carbon tissue
for sale but don't have details. Tissue is practical to make
but requires some special knowledge and is not a casual
process.
   B&W or monochrome carbon or carbro is not especially
difficult although three-color carbon is still a very fussy
process. Carbon prints are very beautiful and are among the
most permanent of all photographic processes.

  As a note: The sort of printing boxes designed for
conventional silver-gelatin contact printing paper are not
suitable sources for POP paper or alternative printing
methods, even the ones like the Morse printer, with UV
lamps. The POP processes need light intensity many times
greater.
  They can be printed indoors using high intensity, high UV
output lamps, or a plate burner. A plate burner is a high
intensity UV source made originally for exposing the
photoresist used for making printing plates. Since other
methods of making these plates are now in use plate burners
often come up on the used market at quite low prices. They
can be used for carbon, oil, Platinum processes, etc.

---
Richard Knoppow
Los Angeles, CA, USA
dickburk@ix.netcom.com