From: Cactus Cowboy (photo@wir.net)
Date: 09/08/00-08:22:44 AM Z
Dear Brahma:
Your second coating, dark green, probably had too much pigment in it. Have
you done a 'stain test' for all of the pigments you use? If not, you
should. You want to use the maximum amount of pigment possible of course,
but not so much that you have excessive non-exposure staining. You might
also try experimenting with different manufacturer's products, both tube
watercolor paints, and powdered pigments. You'll find that some pigments
are terrible for gum printing, others are excellent.
Lack of gelatin on your paper will also promote staining. The gelatin and
formalin treatments are laborious and messy, but the results IMHO, justify
the effort.
Cyanotype is a different process, but similar in that you apply an emulsion
to the paper and expose using the same negative and light source. I won't
get into the details of how to actually do it..... I do have to get to work
this morning! Perhaps somebody out there can provide a link to a site that
explains the process?
Here's an interesting effect to try, using (for example) a B&W neg of a
partly cloudy sky with silhouetted foreground objects:
1. Weak exposure of cyanotype - shadows to darker midtones.
2. Medium exposure of gum w/red or magenta pigment - shadows through
midtones.
3. Strong exposure of gum w/yellow pigment - printing for good detail in
highlights.
The result is a rich purple/black in shadow areas, ranging to reds, oranges,
and yellows into the highlights. A great way to get a really dramatic
'sunset' scene.
Ciao,
Cactus Cowboy
Big Wonderful Wyoming
Brahma wrote:
(snip)
> First coating with Lefranc & Burgois or whatever that brand is called
> Sepia. Everything came out fine.
> Second coating, dark green pigment, same brand as before, same exposure,
> same development, and voila!, that green gook is not going to come off
> that sepia print. No matter what I do. It's especially strong in the
> highlights where it shouldn't be at all. In the end I took a brush and
> rubbed it off, but now the print looks like a Martian had puked on it.
>
> So I wonder what went so right with the first coating, and so wrong with
> the second. I used the exact same amount of gum and dichromate. I dried
> the emulsion under the exact same conditions. I exposed in the exact
> same way.
>
> The only thing I didn't do was coat the paper with gelatin because I
> don't like that stuff. But could that missing gelatin be the reason for
> a first class result in the first coating and a disaster in the second.
> How does one make cyanotypes? Is it an emulsion similar to the one used
> in gum printing? Does one expose it through a negative or a positive?
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