U of S | Mailing List Archive | alt-photo-process-l | Re: direct carbon or gum bleach development

Re: direct carbon or gum bleach development

Keith, it's somewhat confusing because "carbon black" is sometimes used as a general term to designate black pigments made from carbon and sometimes to designate a specific pigment, PBk7, which is why pigment numbers are so important. Lamp black pigment is PBk6; PBk7 is called sometimes carbon black and sometimes furnace black and is sometimes given the marketing name "lamp black," but isn't actually lamp black. According to some sources, PBk7 is darker and velvetier than PBk6.

I've been sick for weeks with a flu thing that turned into bronchitis and haven't got down to the workshop to continue my experiments with this. But because I'm still interested in exploring this, I wonder if you could say a little more about what's not working for you; is it "just" staining, or is it a problem with the bleaching too? Thanks.

On Jan 2, 2008, at 7:41 AM, Keith Gerling wrote:

Thanks Marek,

Cold here in the midwurst and I'm staying put and making do with what
I have at hand (which does not include Fabriano).  But carbon black is
the same as lamp black, correct?  And I also have some pure graphite,
and both of these stain what I've been using, which include Masa (as
predicted by Loris), gessoed paper and wood, and the flip side of
other gum prints on various papers (which, come to think of it does
include Fabriano, albeit many times immersed in water, so it isn't
like what you have used).

Thanks for the offer.  I'll play around a little more.  The picture
you posted was on unshrunk paper, correct?  What impresses me the most
is not so much the bleaching (without seeing a before-and-after it is
hard to tell what that is) but the intensity, shapness and grain of
the print (resembling, come to think of it, a Ralph Gibson...)  What I
would very much like to do would be to produce duotones by using this
process over a Van Dyke print.  What are your thoughts on that?



On Jan 2, 2008 8:09 AM, Marek Matusz <marekmatusz@hotmail.com> wrote:

I have been using carbon black powder from Daniel Smith. Gum bleach
development requires higher density negative then normal gum. I would say
something more like palladium negative density would be fine to start with.
If you can email me a scan of your work I can perhaps troublesoot it.

Date: Tue, 1 Jan 2008 19:47:57 -0600
From: keith.gerling@gmail.com
Subject: Re: direct carbon or gum bleach development
To: alt-photo-process-l@usask.ca

Hi Marek,

My attempts look atrocious. What kind of pigment are you using for this?



On Dec 20, 2007 4:05 PM, Keith Gerling <keith.gerling@gmail.com> wrote:

Awesome, Marek. This is what I want MY prints to look like. Forget
all that multi-coat nonsense.

On Dec 20, 2007 2:28 PM, Marek Matusz <marekmatusz@hotmail.com> wrote:

More experimentation with gum printing and bleach development.

I was intrigued by Loris's results with using unsized paper. I thought


it would give a rather bad stain. My tricolor gum practice certainly

led me

to believe this. However on numerous occasions I did observe that

edges of

paper that I used which did not have gelatin size gave a darker, more
uniform black. SO last week I tried to use single sized paper, fresh


unsized Fabriano Artistico, and a throw away gum print that has been


over and over, but had a reverse side of Fabriano paper quite clean.


overall conclusion with this set of prints is that I liked unsized

paper and

soaked paper best. They gave crispier prints. Perhaps this technique


the gum to be tied up with the fiber of the paper and the bleach


can give clear paper base. So I would advocate use of straight


paper, no need to size. I have not tried any other brand, but I should


some at hand and will try next printing session.

I have also experimented some more with pigment density. I had a more
concentrated carbon stock of 3.75% carbon in 14 baume gum, that is 50%


then in my last set of experiments. The solutions are left over from


or maybe hundreds of experiments done in the last two years. Once the


dried out this would result in 3.75/0.27=14% carbon/solid gum mixture


assume 14 baume gum is 27%). This is definitely black black. Beautiful
velvety matte texture of the deep black to take your breath away. Scan


the print here. This print was made on unsized Fabriano Artistico


http://picasaweb.google.com/marekmatusz1/GumBleachDevelop/ photo#5145909559997921266

The mid tones are a little bit darker on this screen that in reality.


even the two tones of black on the very edge are visible. Very

outside, had

most exposure (I uped the exposure to 6 minutes from last time) and

next to

it is somewhat lighter edge from exposure through blank part of


(Pictorico). This is a further illustration of how a fine tonal


can be achieved with this method.
I have also included an detail of the print scanned at 300 dpi:

http://picasaweb.google.com/marekmatusz1/GumBleachDevelop/ photo#5145909521343215586

Happy printing

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