Re: Gum woes

Your first series, with pigment mixed at 1gram per 3ml of gum, may be too
heavy on the pigment. Try using ratios of 1g/10ml, 1g/15ml, 1g/20ml,
etc...... Also note that one fixed ratio is not suitable for all pigments.
You'll have to experiment with individual pigments at varying ratios for
optimum results. Different pigments will vary widely in printing strength,
tendency to stain, and other factors.

I don't understand Jame's "5-10-10" formula. Why the extra step (mixing 5ml
of AD solution to 10ml distilled water)? Instinct tells me that it would be
a watery and weak emulsion. I've good overall results using 1 part gum
arabic/pigment solution to 1 part sensitizer solution, with exposures
ranging from 2 to 6 minutes in a homemade UV light box. I believe that's
the 'standard ratio' recommended by most authors. Use that as your starting
point. After you master the process, you can then alter your formula,
increasing or decreasing the amount of sensitizer used in relation to
gum/pigment.

Jame's "traditional formula" (9ml gum/pigment to 3ml sensitizer) strikes me
as way too heavy on the gum/pigment.

Try a test print using:

20ml gum w/1g pigment
20ml sensitizer

Have fun.

Dave in Wyoming

----- Original Message -----
From: "Scott Wainer" <swphoto@verizon.net>
To: <alt-photo-process-l@sask.usask.ca>
Sent: Friday, May 06, 2005 11:32 PM
Subject: Gum woes

> Hi all:
>
> For the first time since my "Introductory Alt Process" course at the
University of Maryland I began to take a serious interest in gum printing
and have some problems/questions that I hope the list can help with. I drew
most of my information on gum printing from Scopick's Gum Bichromate Book,
Christopher James' Alt Process book, Katharine Thayer's website, and Sam
Wang's Unblinking Eye article.
>
> To start, I jumped right in with 3-color printing. My process was as
follows:
>
> Making inkjet separation negatives from my RAW files:
>
> 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.
>
> According to Scopick's book, printing from separation negatives I was to
use a complementary color for each separation I made
>
> so I used the following:
>
> Separation Complementary Color Color Used
>
> Blue Yellow Winsor & Newton
Artist Watercolor
> Lemon Yellow
>
> Green Magenta Winsor & Newton
Artist Watercolor
> French
Ultramarine/Cadmium Red Deep
> (mixed
1+1)
>
> Red Cyan Winsor & Newton
Artist Watercolor
> French
Ultramarine/Permanent Sap Green
> (mixed
1+1)
>
> (all pigments mixed at 1gm of pigment to 3 ml of Winsor & Newton Gum
Arabic)
>
> Each separation negative was printed on 4 sheets of paper for different
times. The paper was Daniel Smith Lenox; preshrunk, gelatin sized, and
hardened with chrome alum about a month ago. I mixed the sensitizer using
James' "5-10-10" formula for a texturally smooth coating:
>
> 10 ml gum arabic / pigment (see above)
> 10 ml distilled water
> 5 ml ammonium dichromate, 25% solution
>
> Each sheet was processed as follows:
>
> First coat: Yellow
> Emulsion: brushed on with a hake brush and smoothed until just
tacky.
> Dry Time: 30 minutes by cool air fan in dark.
> Exposure:
> Sheet 1: 1.5 minutes
> Sheet 2: 3 minutes
> Sheet 3: 6 minutes
> Sheet 4: 12 minutes
> Development: 3 still water baths for 30 minutes, 20 minutes, 10
minutes.
> Dry Time: 30 minutes by cool air fan in dark
>
> Second Coat: Magenta
> Emulsion: brushed on with a hake brush and smoothed until just
tacky.
> Dry Time: 30 minutes by cool air fan in dark.
> Exposure:
> Sheet 1: 1.5 minutes
> Sheet 2: 3 minutes
> Sheet 3: 6 minutes
> Sheet 4: 12 minutes
> Development: 3 still water baths for 30 minutes, 20 minutes, 10
minutes.
> Dry Time: 30 minutes by cool air fan in dark.
>
> Third Coat: Cyan
> Emulsion: brushed on with a hake brush and smoothed until just
tacky.
> Dry Time: 30 minutes by cool air fan in dark.
> Exposure:
> Sheet 1: 1.5 minutes
> Sheet 2: 3 minutes
> Sheet 3: 6 minutes
> Sheet 4: 12 minutes
> Development: 3 still water baths for 30 minutes, 20 minutes, 10
minutes.
> Dry Time: 30 minutes by cool air fan in dark.
>
> 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.
>
> 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 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
>
> (all pigments mixed at 1gm of pigment to 3 ml of Winsor & Newton Gum
Arabic)
>
> Again I ran into the same problems as before; almost exactly. Could it be
the paper, the sizing, the pigments, the sensitizer formulas; or a
combination? Any help would be appreciated.
>
> TIA, Scott
>
> Swphoto@verizon.net
>
>
> PS:
>
> Looking through my collection of paints, I found the ones listed below and
wondered if anyone could shed some light on which ones to use.
>
> Winsor & Newton Designer Gouache
> Alizarin Crimson Permanence B Series 1
> Permanent Green Deep Permanence B Series 2
> Burnt Umber Permanence AA Series 1
> Lemon Yellow Permanence A Series 1
> Phthalo Blue Permanence A Series 1
> Ivory Black Permanence AA Series 1
>
> Winsor & Newton Artist Watercolors
> Cadmium Red Deep PR108
> French Ultramarine PB29
> Permanent Sap Green PG36/PY110
>
> Grumbacher Academy Watercolors
> Ultramarine Blue PB29
> Prussian Blue PB27
> Lamp Black PBk6
> Thalo Red PV19
> Grumbacher Red PR170/Pr188
> Lemon Yellow PY3
> Cadmium Yellow Medium Hue PY3/PY65
> Sap Green N/A
> Hooker's Green Deep Hue PG36/PB15:4/PY97/PY65?PBk6
> Chromium Oxide Green PG17
> Burnt Umber PBr7
> Raw Umber Hue PBr27/PBr7/PY42
> Van Dyck Brown PBr7/PBk6
>
>
>
>
Received on Sat May 7 08:25:19 2005