Re: Full color gum printing

From: Joe Smigiel ^lt;[email protected]>
Date: 07/05/04-08:24:08 PM Z
Message-id: <>


Ahhh. Now I know what you are doing with the bleach. From my
understanding of the gumoil process, chlorine bleach is used to remove
hardened gum from the paper substrate. In gumoil this is done in a
stepwise fashion to reveal more of the paper substrate so that oil
pigments can be applied to the paper. The hardened gum acts as a
physical resist, repelling the application of oil paints in those areas,
and by successively bleaching it back, new areas of the paper can be
pigmented. (The hardened gum is printed from a positive rather than a
negative, thus creating a negative mask on the paper, and the different
oils build up a positive image on the paper substrate in gumoil, IIRC.)

The clearing agent (potassium metabisulphite) in the typical gum
bichromate process does not remove the gum layer but rather just the
dichromate image. The hardened and pigmented gum layers are left

Chlorine bleach might also remove the dichromate image, but I suspect it
would do so at the cost of removing part of the desired pigmented gum
image. This sounds like what is happening to your bleached prints. I
would not use bleach unless I really wanted to remove/bleach back a part
of the gum image. That is a quite different operation than clearing the
print in potassium metabisulphite.


>>> 07/05/04 7:45 PM >>>
Clorox and water (1:4) for 10 seconds.
I learned from Gumoil but very dificult to go back to quality.

Anyway I will try with the clearing and dry the picture one more day.
The other issue may be the pigment, some are good and some are
It started happening to me with Sonnellier but then it went fine.

----- Original Message -----
From: "Joe Smigiel" <>
To: <>
Sent: Monday, July 05, 2004 6:11 PM
Subject: Re: Full color gum printing

> Hello Giovanni,
> I usually wait to clear the print until after my final layer is
> although I have cleared after an intermediate step. Although I have
> never tested it, I sense that the printed gum layers are softened by
> clearing agent until the print is subsequently dried which hardens the
> gum again. So, I would wait until the end and print expecting the
> clearing agent to remove the subtle dichromate image and shift the
> away from the slight greenish cast that the dichromate imparts.
> If you cannot wipe the gum image layer away while it is in the wash,
> are probably giving that layer too much exposure. What I'm suggesting
> is a very faint layer of low pigment concentration which subtly shifts
> the color balance and which should autodevelop to the desired result.
> Since the exposure is planned for autodevelopment, any physical
> manipulation (brushing, water stream, hot water, etc.) should remove
> just-printed layer and leave the previous image intact with no harm
> done.
> If yellow-green shows "in abundance" the color imbalance is probably
> due to the dichromate image alone but rather some mismatch between
> pigment strengths and saturation of the various layers. The greenish
> dichromate image is very faint when present.
> I have never used bleach on a gum print so I'm not sure to what you
> refer. Sodium hypochlorite (chlorine bleach) perhaps?
> Joe
> >>> 07/05/04 4:09 PM >>>
> Hi Joe,
> Thanks, it rings my bell.
> Are you suggesting that if during exposures some yellow-green shows
> abundance) to clear it before going to the following exposure?
> Then you suggest "to wipe it off and wash" but once exposed is very
> difficult, I use some hot water and not always everything comes off.
> I
> bleach I ruin everything.
> What do you mean with that?
> Thanks,
> Giovanni
> ----- Original Message -----
> From: "Joe Smigiel" <>
> To: <>
> Sent: Monday, July 05, 2004 1:12 PM
> Subject: Re: Full color gum printing
> > Giovanni,
> >
> > Have you tried clearing the print in a solution of potassium
> > metabisulphite or similar clearing agent? I've found a slightly
> > greenish cast results from the accumulated dichromate image (which I
> > believe others on the list refer to as "dichromate stain") followed
> a
> > wash. You might also try a lightly printed magenta layer to
> neutralize
> > the color cast and adjust the overall color balance. I suggest
> magenta
> > since your description of the problem appears to center around a
> > imbalance and magenta is its complementary color. (With pigments, G
> > Y+B)
> >
> > If you are familiar with chromogenic printing and have a set of
> > viewing filters around, you might be able to better determine if the
> > present color imbalance is more to the green, yellow, or blue, and
> then
> > choose a more appropriate corrective pigment choice. It is
> to
> > suggest more without knowing how the color imbalance is appearing.
> For
> > example, are the shadows too blue and the highlights too yellow with
> > green midtones? Each of these tones present a different quandary
> > require a different solution.
> >
> > I certainly would not throw the print away since it is difficult to
> ruin
> > a gum print by doing another lightly printed layer. If it doesn't
> look
> > correct, you can just wipe it off in the wash and do another layer.
> The
> > danger is overexposing the corrective layer so that it cannot be
> removed
> > with a bit of physical manipulation in the wash.
> >
> > Joe
> >
> > >>> 07/05/04 10:55 AM >>>
> > I am trying to figure out what adjustments can be done to an almost
> > finish
> > full color gum print but unfortunately with either slightily too
> > yellow, green or blue on the image.
> > If you have experienced the process you may have run that the
> > may
> > had some problems or the expoure did not come out as planned and you
> > ended
> > up with this almost complete print but with a slightly different
> color.
> > My thoughts are than instead of throwing it away and start all over
> > again is
> > worth to try to fix it.
> > Any idea or experience you would like to share on this subject?
> > Thanks,
> > Giovanni
> >
> >
> >
Received on Mon Jul 5 20:23:53 2004

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