Re: Gum woes

Hi Christina,

Sorry for not responding to your post earlier, I never got it; had to go to
the list's "live mirror" to read it after seeing Joe's post.
> Where to start, where to start, Scott: I don't convert RGB to greyscale, I
> do all my adjustments, invert, curve, and then I split channels. I do
print
> my negs out in black ink only.

Since this was my first real attempt at gum (being extremely colorblind I
have stayed away from color processes) and my first time doing separations,
I kind of winged it; not being sure of where to start. I visited Katharine
Thayer's site and read that, in respect to curves for tri-color printing,
she "... found that for inkjet I didn't need to make any adjustment to the
file for printing the separations, once I had the color image the way I
wanted it" so I didn't even try applying a curve. I'll have to try applying
a curve and see how that looks. Is your curve close to that used for
printing on silver gelatin? As for converting to grayscale, I guess it's
just an extra step once you select a channel but I wanted to make sure that
the other channels were gone. It doesn't seem to make a difference one way
or the other. I tried printing with black ink only but the negative was much
smoother using all the colors.

> I print blue first with the red neg, yellow next with the blue, magenta
> third with the green neg. I have never used green pigment. I use a nice
> primary yellow, biased more towards golden than green. I use a nice
primary
> magenta, biased more towards red. I use tube colors, not pigment powder.

This might be where I went "wrong", I couldn't find any definite "written in
stone" answer from the sources I found to what color to print with which
separation or in what order to print. Looking at Scopick's "Theory Of
Printing From Separation Negatives" (pg. 70) I figured that for RGB
separations I should print yellow for the blue, magenta for the green, and
cyan for the red negative. Since I had Lemon Yellow I used that for the
blue. I mixed blue and red as magenta for the green and blue and green as
cyan for the red. I just went in the order he had everything listed using
tube watercolors.

> I just gave my formula in my post on "was cyano now gum recipe" so I won't
> repeat.

I'll look that up and give it a try also.

> Grained up--are you using powdered pigment? This has happened to me with
> powdered pigment, too. Or as Joe says, could be overexposure that gets it
> looking gritty. I think I, as Dave says, used too much powder and didn't
> dissolve it well. Dave has a special mixer, the old timers used to use a
> mortar/pestle to grind up the pigment into the gum. I used my food
> processer, but what a mess. Now I stick to tubes, but Dave does beautiful
> prints with powder.

No, i'm using some old tubes of Winsor & Newton artist quality watercolors
that I had left over from a watercolor course about 6 or 7 years ago. They
were tightly sealed and still soft so I figured i'd use them up first rather
than buy new ones. Exposure for each color was between 2-4 minutes. With
help from Joe Smigiel, Marek Matusz, and Dave Rose I think my pigment/gum
ratio and amount of dichromate were the main problems. Increasing the
pigment/gum to 1g/20ml and mixing it 1+1 with the dichromate made for much
easier coating.

> It is hard to judge from your description what exactly is happening, but
if
> I am correct in evaluating your descripton, here's my guess:

> This happened to me, too, two causes: improper and uneven sizing with
> chrome alum or acrylic so sizing was on top of paper and unevenly slick
and
> spotty; or, if sizing was even, if I diluted my gum/pigment/di mix too
much
> and it lost its adhesion viscosity or something or other and pulled apart
in
> fisheyes. I would keep brushing it until some of the moisture disappeared
> into the paper. Oh, maybe a third, when the layers built up enough so the
> hardened gum surface was slicker.

> I have read about this in old books and one author said on the microscpic
> level the gum had beaded up in a ball and some such other thing, but I
don't
> have a microscope. If you check under "fisheyes" in the archives there was
> a discussion about this a year or so ago, maybe last summer?

I guess now that I have the pigment/gum ratio and amount of dichromate
pretty much under control my main problem is still the "graining up" which
seems to happen with all colors I have tried. The only way I can describe it
is to say that it looks like the pigment is separaing from the
gum/dichromate when it is applied to the paper. It gets a gritty/grainy look
almost like that of an infrared negative that has been greatly enlarged. I
thought maybe I hadn't mixed the pigment/gum enough so I mixed it again for
about 20 minutes and still got the same thing. I had thought maybe the
problem was the quality of the watercolors, but they are all artist quality.
I am of the oppinion now that it must be the age of the pigment but I can't
test that theory until Monday when I can get fresh tubes.

> Tell me, were you reall printing each neg with its own color? What did it
> look like??

Again, being extremely colorblind, I don't really know how to describe them.
All I can say is that they are images of plants like Hosta, Azaleas, and
cherry blossoms. I'm trying to get a page up with my ISP so I can post them
but i'm not having much luck right now. If you or anyone would like, contact
me off list and I can scan and email them to you.

Thank you for the help, Scott

swphoto@verizon.net
Received on Sun May 8 12:40:38 2005