Re: clearing/hardening carbon images

Luis Nadeau (nadeaul@nbnet.nb.ca)
Fri, 10 Apr 1998 14:41:02 -0300

At 5:53 PM -0300 98/04/08, Tom Hawkins wrote:
>Dear Listmembers,
>
>Thanks to the collective wisdom of the list, and a few days of concerted
>effort on my part, I've just completed my first successful group of
>monochrome carbon images. There are a number of refinements that still need
>to be made, but these initial results are very gratifying.
>
>As a test, I tried several exposures using digital negatives designed for
>platinum printing. The results are promising. Adjustments need to be made
>to the platinum curve, but exposure times appear to be consistent from one
>negative to the next.

Let me know if you get excellent monochrome carbon transfers from digital
negs. A few people said they'd send me some small specimens but nothing has
ever materialized yet.

>I would appreciate some clarification concerning the clearing/hardening
>steps of the process. Some texts mention a clearing bath of chrome alum,
>while others suggest that alum may be detrimental to the archival properties
>of the print.

Simply wash it out. I have seen hundreds of 19th century carbons and 99%+
are in excellent shape.

"Keepers of Light" suggests sodium bisulfite or potassium

An overall excellent book but not written by a specialist who used the
process for a living.

>metabisulfite instead of the alum. "Keepers" also suggests that formalin

the sodium bisulfite and potassium metabisulfite will clear your prints but
will soften your carbon images considerably. After clearing rinse the
prints several times with cold water and harden them. Rinse them again with
several changes of water over a period of say, 30 minutes, after hardening.

>may be used as a hardening agent, though a hardening step is not really
>necessary. M.Nadeau's text indicates that a hardening bath is a necessary
>step.

It is certainly recommended.

Luis Nadeau
NADEAUL@NBNET.NB.CA
Fredericton, New Brunswick, Canada
http://www3.nbnet.nb.ca/nadeaul/