Re: Gum prints with the enlarger

Luis Nadeau (awef6t@mi.net)
Sat, 20 Apr 1996 17:55:06 +0300

..>Conscience may prod one to share findings by putting them in the public
>domain - it has the benefit of forestalling the kind of unpleasantness
>we've just witnessed - but with a pension from a life's teaching, I can
>afford to be generous to those who expect something for nothing. Phillipe
>Berger, who claims to have the enlarging-speed gumbi process, may not be so
>fortunate. (We are seeing a similar spat here in the UK at present, with a
>different "secret" pigment process.)
>
>If what is claimed is true (Klaus - have you any quantitative details about
>exposure?), it's certainly worth *far more* than a measly $400, and the
>chap should have no difficulty exploiting it and making his fortune. As

I agree that the amount is ridiculous if it has any real commercial
application. This is why I suspect it doesn't, perhaps because it is
limited to "gum" as a colloid, which would be very strange indeed since
conventional sensitizers, e.g., dichromate and diazos affect just about
everything from albumen to PVAs.

>Judy said - it's a once-in-a-hundred-years discovery. Just think what it
>could do for the commercial maker of permanent colour prints (e.g.
>UltraStable or EverColor), or holography (for which the best medium is

Not really. As a matter of fact, EverColor has turned down this
possibility! When I learned about their "new" process I quickly put 2 and 2
together and mentioned to them that the process was not new at all. I'll
try to explain this to the non-initiated here:

Using ordinary enlargers to obtain pigment images is nothing new under the
enlarging lamp. In Nov. 1907 the Rotary Photographic Co of England
introduced a material manufactured according the patents of NPG (Neue
Photographische Geschellschaft) of Berlin, and consisting of an emulsion
containing *BOTH* a silver bromide and a pigmented emulsion. An ordinary
negative could be enlarged on it. The resulting image was basically a
carbro print... This pigment paper was on the market until 1913.

In 1929 Herzog in Germany came out with a color version. The materials
(Duxochrome) were available until the 1960s. In the US it was marketed
under the name Colorstill. In 1955 a different version was marketed under
the name Duxocolor. It allowed the three colored gelatin reliefs to be made
directly from a color negative instead of monochrome color separation
negatives.

The current EverColor does not use a projection speed silver emulsion for a
number of reasons: Graphic arts scanners, printers, imagesetters, etc., are
designed to produce *large size* films for the graphic arts industry that
uses pin registration systems and does not like using real *darkrooms*.
Their material is slow enough that safelights are quite bright so
technicians can move around freely and see what they are doing. So, despite
the fact that the technology (projection speed pigment materials) has been
around for nearly a century, those who might have a need for it choose not
to use it...

>dichromated gelatin) or the use of photoresists in the printing industry,
>or digital imaging.
>
>The fact that it is being offered to amateurs for so little, makes me dubious.
>
>Photo-hardening of colloids like gum, gelatin and PVA is not my field, but
>I know that there has been a lot of professional research out there, with
>folk trying to sensitise the processes up to 'projection speed' for obvious
>commercial motives. I have seen a number of published papers on attempts to
>use dye sensitizers to achieve this. And it's anyone's guess what is
>happening behind the closed laboratory doors of big K, A, F or I, etc. Is
>there no-one on this list who is close to this kind of research and can
>comment on the current state of the art? The C19th Gumbi process that we

I was keeping a eye on this in the patent and scientific literaure until
about 1982 when my first book on carbon printing came out. At that time, as
you said, most of the research was concentrated around dye sensitizers
(sure did wonders to the Ag industry at one time!) but the order of
magnitude was nowhere enough to achieve projection speed.

>all know and love, might actually be back among the dinosaurs.

I'm trying to invite Berger to Paris for the May 4th Alt-photo meeting. If
he shows up, we'll sure have a report on this list... I do hope he has
something really new.

BTW, are you coming over to join us Mike? (Reply offlist if you wish)

Luis Nadeau