Re: Gum woes

From: Christina Z. Anderson ^lt;>
Date: 05/08/05-07:04:48 AM Z
Message-id: <002a01c553ce$866a29c0$6101a8c0@your6bvpxyztoq>

<big snips> 1. Adjust exposure, color, shadows, and open image in 16
bit at
> 17x25 @ 240dpi.
> 2. Select RGB color channels one at a time and convert to
> grayscale.
> 3. Invert image.
> 4. Set size to 5x7 at 300dpi.
> 5. Print on Westjet transparency using an Epson 1280 with pigmented
> inks.

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.

> According to Scopick's book, printing from separation negatives I was to
> use a complementary color for each separation I made

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.

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

> What I noticed was that the sheet exposed for 3 minutes for each color was
> the "best". I found that the yellow coat went down very smoothly and had a
> "creamy" texture. The magenta and cyan coats were much harder to get
> smooth and "grained up" - almost like the look of a 35mm infrared negative
> enlarged to 20x24.

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.

> I tried printing the same as above but changed the sensitizer to James'
> "Traditional Formula":
> 9 ml gum arabic / pigment (as above)
> 3 ml ammonium dichromate, 25% solution
> The coats were very hard to apply and get smooth. All seemed to "bead" and
> "grain up" like there were spots of oil on the paper and "pulled" in areas
> like the gelatin sizing was not hardened and was coming up and mixing with
> the sensitizer.

I have never mixed gum and am di that thick, but then again, my gum is
pretty thick (1+2 water at most, sometimes 1+1 or 1+3). I don't know what
James' gum mix is like--maybe it is watery?

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 tried printing the negatives again this time using both sensitizers and
> pure tube colors (no mixing colors):
> Separation Color Used
> Blue Winsor & Newton Artist Watercolor
> French Ultramarine
> Green Winsor & Newton Artist Watercolor
> Permanent Sap Green
> Red Winsor & Newton Artist Watercolor
> Cadmium Red Deep

Tell me, were you reall printing each neg with its own color? What did it
look like??
Received on Sun May 8 07:05:03 2005

This archive was generated by hypermail 2.1.8 : 06/02/05-10:12:02 AM Z CST