Re: Newbie Gum fun Continued
Clarification: My earlier characterization of ivory black wasn't
quite complete:
I actually prefer ivory black to lamp black, because it's a
transparent color while lamp black is quite opaque, and I prefer
transparent pigments to opaque pigments. But when I use it as a
black (as opposed to capitalizing on its brown characteristics as in
the example I showed earlier) I mix blue with it (usually Prussian)
to counteract the warmth and make the greys more neutral, or
sometimes I take it more cool by adding more Prussian beyond the
neutral point, to result in a transparent blue-black.
kt
On Apr 25, 2007, at 7:34 AM, Katharine Thayer wrote:
On Apr 23, 2007, at 10:42 PM, Jacek wrote:
Hi Katharine
The lamp black is Windsor and Newton, any suggestion for another
type of black tube paint from them you would recommend in getting
a nice jet black colour? Ivory black or Neutral tint by W&N perhaps?
Ivory black is an easier color to work with, but tends toward brown
rather than grey in all tones but the darkest (see
http://www.pacifier.com/~kthayer/html/kids.html
for an example of a gum print in ivory black) so if you want
neutral greys, it may not be the best choice. But if you want a
rich brown, it's a very good choice. So depends what you're after.
Another question I have is with the Potassium Dichromate, is it
worth reducing the saturation of this to get a longer tonal scale?
What would I be missing out if I reduced it?
In my experience, reducing the dichromate concentration will
reduce, rather than lengthen, the tonal scale (you get fewer steps,
rather than more). See
http://www.pacifier.com/~kthayer/html/Dichromate.html
for a discussion of the relationship between dichromate
concentration, speed, and contrast, with examples. So if you want
a longer tonal scale than you can get with saturated potassium
dichromate, you should consider going to ammonium dichromate.
I guess time for exposure would be more, that is if I used exactly
the same amount of gum and pigment, as I did for the same
saturated solution of Potassium Dichromate.
Yes, diluting the dichromate increases the exposure time.
My understanding would be to change the negative using the
photoshop curve to get the full graduation of tonal scale and
leave the Potassium Dichromate saturated as it is.
The only 2 variables I should worry about are the Gum and Pigment.
Is this assumption correct or partly correct or just try it and
see where it takes me :)
Well, the main thing is to try not to change more than one
variable at a time, so that you can see the effect of each
variable. Good luck,
Katharine
On Apr 23, 2007, at 10:42 PM, Jacek wrote:
Hi Katharine
Thanks for the info. I'll test the Arches paper tonight with the
boiled up shrinking and let you know how I go.
I haven't used any hardeners as yet because I can't seem to find
any here in Perth, still looking..
The lamp black is Windsor and Newton, any suggestion for another
type of black tube paint from them you would recommend in getting
a nice jet black colour? Ivory black or Neutral tint by W&N perhaps?
The gum solution was 33%. I used 5ml of that with 2 small dots of
Windsor and Newton lamp black. With 5ml Potassium Dichromate
Saturated Solution.
I'll try my hand at reducing the lamp black and see what I get.
I'll try the foam padding under the paper to get the maximum
contact of the negative and glass.
Another question I have is with the Potassium Dichromate, is it
worth reducing the saturation of this to get a longer tonal scale?
What would I be missing out if I reduced it?
I guess time for exposure would be more, that is if I used exactly
the same amount of gum and pigment, as I did for the same
saturated solution of Potassium Dichromate.
My understanding would be to change the negative using the
photoshop curve to get the full graduation of tonal scale and
leave the Potassium Dichromate saturated as it is.
The only 2 variables I should worry about are the Gum and Pigment.
Is this assumption correct or partly correct or just try it and
see where it takes me :)
Thanks
Jacek
On Tue Apr 24 1:55 , Katharine Thayer <kthayer@pacifier.com> sent:
Hi Jacek,
Perhaps I wasn't clear in communicating my experience with Arches
paper before. There are two issues: (1) in my experience, Arches
paper as now formulated can't be printed unsized because of
speckles. If you got a good result by shrinking it with boiling
water and printing unsized, that's interesting, and inconsistent
with
what I've seen before. The rule with gum is, use whatever works; if
boiling water works for you, go for it. My experience has been that
treating with very hot water just messes with the internal gelatin
size, but that's the thing about gum, we often get contradicting
observations. (2) When sized, my experience is that the sizing for
Arches should be kept below 140 or I get speckles in the sized
paper,
but as people are always saying, your mileage may vary. I harden
with glyoxal.
About your problem with incomplete contact, it may not be that the
glass isn't heavy enough; your problem may be on the back side of
the
paper. When I first started printing gum, I had the same problem; I
had a piece of smooth wood on one side of the paper and a piece of
plate glass holding the paper to the wood, but I had areas in the
print where it was obvious there was inconsistent contact. I got
some interfacing from the fabric store, sort of a webby stuff, but
foam rubber or something similar would probably work as well, to
place between the wood and the back of the paper, and that's all
I've
used ever since to get good contact. It holds the paper securely
against the glass.
Two pea-sized pieces of lamp black in how much gum? What brand of
lamp black? I might be inclined to guess just on general principles
that you may be using too much pigment, only because in my
experience beginners almost always use too much lamp black to start.
Lamp black is a very powerful pigment; a little goes a long ways.
Try cutting your lamp black by half by adding more gum; if you still
get a dark black where you want a dark black but no staining, then
the staining was probably due to too much pigment rather than
insufficient sizing. I've got an example on my website that shows
the difference between way too much lamp black and half that
much, if
you want to compare what you're observing:
http://www.pacifier.com/~kthayer/html/stain.html
I coat paper in daylight or under a 60-watt tungsten light with no
problem; a safelight isn't necessary. Just don't do it in direct
sun.
Katharine
On Apr 23, 2007, at 9:17 AM, Jacek Gonsalves wrote:
Hi all,
Well I finally took the plunge on the weekend and did my first ever
print in gum.
The results were...well something actually came up and I can see I
have
a long way to go! :)
I used W&N lamp black tube, found I couldn't weigh it on my scale
when I
squeezed 2 pea sizes out, nothing registered on the scale! :)
The paper itself got stained perhaps of too much pigment or
because I
didn't add enough gelatin to the paper?
My paper seemed to have curled and the negative seems to not
have sat
comfortably on it, even with a heavy glass on. I might have to put
something heavier or try keeping the paper flat when drying with
all the
preshrinking and gelatin. Perhaps I can find plans on the net to
build a
Contact Frame?
The Arches paper Smooth 300gsm, I had an issue with dotted
speckles, I
found that the water preshrinking I used wasnt that hot. The water
couldnt penetrate the whole paper, therefore getting speckles in
the
paper. Also the fact I was preshrinking for only 10 mins.
I used this paper to develop a print, and the part where you can
see the
dotted speckles, has been stained with the lamp black pigment, the
rest
seemed unstained.
I ended up using boiling water to preshrinking another batch of the
same
Arches paper, and I got no more speckles! Though I might have
damaged
the actual manufacturers hardening of the paper? Also it really
gave off
fumes with the boiling hot water, I had to take it outside.
I tried a batch, Katharine suggestion of below 140F(60C),
unfortunately
it still has the dotty speckles. I changed the water at least 4
times,
their still there! :(
Reading the Altlist I see some people just use lukewarm water to
preshrinking?
Also what paper do you use and how do you preshrinking it? With
boiling
hot water, lukewarm water etc?
I also tried Acquarello Fabriano cold press with no preshrinking, a
brushed on gelatin on one side. Developed the paper and got
staining.
Perhaps another gelatin coat would have fixed it or less pigment?
I'm not using any hardners in my gelatin and perhaps that could
also
account for the staining.
Is a RED safelight, ones used in the darkroom safe to use when
coating
gum? What do you use?
More to come...
Thanks
Jacek
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