Re: Gum woes

From: [email protected]
Date: 05/07/05-07:42:14 AM Z
Message-id: <3966.66.94.133.158.1115473334.squirrel@qmail.pdq.net>

Scott,
If you are interested in photo-realistic tri colour I would suggest that
you try "primary colors first". Phtalo blue (any manufacturer) for cyan,
any PV19 (My favorite is quinacridone rose from Daniel SMith) for magenta
and PY97 yellow (hANSA YELLOW MEDIUM FROM dANIEL smITH). There are a
couple other yellows that I use that work just as well.
Keep in mind that with gum everybody has to work their own workflow.

Marek Matusz

> 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 07:42:23 2005

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