Re: Help with gum pritns on black paper with white Gouache.

Dave Soemarko wrote:
>
> Hi Katherine,
>
> I agree that the grinding might be different, and it is natural to think
> that the pigment for gouache is grind less because it is intended to be used
> opague, but the difference might not be that much for our use (though upon
> close examination you might be able to tell as you have tried it); but I
> think it is still transparent enough to make full-range prints.

Hey Dave,

Apparently I didn't say clearly enough what I meant about the difference
in grinding; in fact the pigment is ground finer for gouache than for
watercolor paint, in order to accomplish the trick with the light
reflection that makes the paint appear more opaque.

I agree absolutely that gouache is "transparent" enough to make a
full-range print. For me there's a difference in how that "transparency"
is expressed, though. Transparent pigments simply disappear into a
darker background. For example, the apricots on my index page (I am so
glad I've finally got a website so I can use it for examples to
illustrate what I'm talking about here):

http://www.pacifier.com/~kthayer/

After I did the three layers of the tricolor, I decided that it needed
more yellow in the apricots, so I printed another layer of full-strength
yellow (PY 110 of course) over the completed print. In the black areas
at the right of the print, there is a layer of full strength yellow on
top of the black, but you can't see it at all because the PY110 is a
fully transparent paint. The yellow is exactly the same concentration as
the sample print of PY110 at the bottom of my page on pigments. So it's
not that the yellow is printed less concentrated that makes it
transparent, it's its *transparency* that makes it transparent. To check
the concentration that was printed,

http://www.pacifier.com/~kthayer/html/pigment.html

But if you printed an opaque yellow on top of the black, you would see
it as a thin veil or a thicker more opaque layer of yellow over the
black, depending on the concentration of the pigment in your mix. I
don't have an example of that to show, because as a rule I tend to avoid
opaque pigments. But you can see it in white in the thing I posted
yesterday: in the background area of the print on sized paper there is a
very slight cloudy white tone to the background. This isn't a stain;
this is tone that was created by a not-quite-solid black in the
negative.

http://www.pacifier.com/~kthayer/html/Whiteblack.html

To summarize this point, transparent pigments are transparent and will
be invisible over a darker background no matter how concentrated they
are printed; opaque pigments are opaque and will be visible over a
darker background no matter how thinly they are printed. Transparent
colors are not visible independently of the underlying color, and opaque
colors are always somewhat visible as a separate color; when you look at
the opaque overlay you see two different colors, one over the other.
Of course there are many pigments that are in between (semi-transparent
and semi-opaque) which will give effects that are somewhere in between
the two extremes. The transparent pigments interact with the underlying
color by blending with them; the opaque pigments interact with the
underlying color by thinning the opaque layer enough that the underlying
color is allowed to show through, but the effect is completely
different. That's why when people ask whether they should use one or the
other type of pigment, I always say it depends on what effect you want
to achieve.

> As for additive, however, W&N literature specifically said that they don't
> add additive to increase the opacity and that they use more pigment instead.

I read this differently than you do; I read it to mean that they don't
add fillers like white chalk like the makers of cheaper gouaches do. But
of course they add other ingredients; all paints add some other
ingredients, as Judy taught me. Even the best watercolor paints don't
contain just gum and pigment, they've got other stuff in them too that
they don't tell you about. The best paints don't use fillers, but they
do use binders and things that make the paint flow well and other stuff.
This is true of both watercolor paint and gouache, and it's these
mystery ingredients that are altered between the two types of paint to
create the opaque effect of the gouache. Yes, makers of fine quality
gouache use more pigment, but that alone would not make a transparent
pigment opaque; the opacity is created by a combination of the milling
and the added ingredients that together make the light reflect
differently.

> That's probably because nowadays there are many gouache artists that use
> gouache to create their arts (whereas in the old old day gouache is mostly
> used for temporary poster or something to be photographed).
>
> But of course one need to check the ingredients. For example, I was mainly
> talking to pigments like burnt sienna used in watercolor versus the same
> burnt sienna in gouache. That would be the same except perhaps for grinding.
> But just the name of the color itself doesn't tell much.

Well, of course, the name of the paint color doesn't tell much, but the
name of the pigment tells everything, and when I give the name of a
color, I'm always naming the pigment. When I name paint colors, I put
them in quotes and identify them by brand. When I refer to names
otherwise, I'm always referring to the name of a pigment. And BTW, I
wouldn't buy any paint that didn't list the name of the pigment(s) used
right on the tube.

 For example, some
> magenta in the gouache line has dye added to make it look better.

> To achieve opacity, one does not always have to add other ingredient that
> makes it opague though. One could, for example, make the gum thicker and
> have more concentration of pigment. That is one reason why gouache is
> usually painted thick. You can see and feel the thickness of it, whereas in
> watercolor, the layer is so thin. So in that sense, if you use a transparent
> watercolor and lay it down thickly, especially if you lay down a few layers
> taking care of not disturbing the layer beneath it each time you layer, you
> can achive opacity with transparent watercolor even though it is not
> intended to be used that way.

No, a transparent pigment is transparent no matter how thickly you lay
it on; at least in gum printing you can never make a transparent pigment
heavy enough to completely block the light, because if you printed it
that thickly it would just flake off in development.

If you're interested in learning more about opaque and transparent
pigments in gum printing, see my section on opacity vs transparency on
my pigment page. This section isn't completely finished yet, because I
have always intended to add some more illustrations, for instance a
visual showing the difference between a tricolor print made with
transparent pigments and one made with opaque pigments, but I haven't
had time to get around to that and I think there's enough information
with the visuals that are there to make the point.
Katharine

> ----- Original Message -----
> From: "Katharine Thayer" <kthayer@pacifier.com>
> To: <alt-photo-process-l@sask.usask.ca>
> Sent: Tuesday, January 18, 2005 7:27 AM
> Subject: Re: Help with gum pritns on black paper with white Gouache.
>
> > Dave Soemarko wrote:
> >>
> >> > BTW, I did used to print with gouache, as there were some
> >> > **gorgeous**
> >> > hot pink, purple, and orange colors I liked. Then someone questioned
> >> > their archivalness so I quit.
> >> > Chris
> >>
> >> Chris, the question about gouache's archivalness is probably due to some
> >> readings in old materials. Gouache used to be cheap poster colors with
> >> fugitive pigments or dyes and white added (for opacity). Nowadays if you
> >> buy
> >> artist gouache (for example, Winsor and Newton), they are basically the
> >> same
> >> as watercolor except that the concentration is higher for opacity reason.
> >>
> >> And for the same reason, gouache can be used for gum printing for opague
> >> or
> >> transparent look. It all depends on how much you use.
> >>
> >
> > I haven't seen the post that this refers back to, but I'll just chime in
> > with a ditto for what Dave says about archivality of gouache. The cheap
> > designer's colors, sometimes called gouache, are mostly made with
> > fugitive pigments and are notoriously fugitive. But the lack of
> > archivality is a function of the pigment, not of the fact that it's
> > gouache. It's the same with artist's watercolor paints vs artist lines
> > of gouaches: the paint is as archival as the pigment it contains.
> > Alizarin crimson in watercolor is fugitive, as is alizarin crimson in
> > gouache. But phtalo is as permanent in gouache as it is in watercolor
> > paint.
> >
> > But I would disagree with the statement that artist's gouaches are just
> > more concentrated versions of watercolor paint. Gouaches are
> > specifically formulated to be opaque. It's true they do tend to use
> > more pigment, and to mill the pigment differently, but they also change
> > other ingredients to render the paint more opaque. The cheap designer
> > colors render the paint opaque by adding white chalk to the paint; the
> > better artist lines render the paint opaque by the way the pigment is
> > milled and by the manipulation of other ingredients to change the way
> > the light reflects off the surface of the paint. I used to think that
> > all gouache had some white added, but I later learned that this is true
> > only of the cheaper gouaches. The way the manufacture of the better
> > gouaches was described to me (by Arthur Graham of M. Graham paint) the
> > resulting paint bounces the light rays around on the surface of the
> > paint rather than transmitting it through the paint and reflecting it
> > back to the eye the way it would happen with transparent watercolor, and
> > the scattering of the light rays at the surface is what gives it the
> > matte or opaque-like effect.
> >
> > No matter how concentrated you make a transparent pigment, it will
> > always be transparent, because that's the inherent nature of the
> > pigment.( The analogy I use on my website to help people see the
> > difference between transparent and opaque pigments is to think of the
> > difference between agates and shale. You can see through an agate even
> > though the material is very hard and solid. But you can't see through a
> > piece of shale, because it's opaque, not transparent.) So to make a
> > gouache, which is intended to be opaque, using a transparent pigment,
> > you would have to render it opaque somehow, either by adding chalk to
> > it, as they do with cheap gouaches, or by milling it differently and
> > adding different ingredients to change the way the light reflects from
> > it, as is done by the makers of the better lines of gouache.
> >
> > Whether you can get the same effect with either transparent watercolor
> > or opaque depending on how much you use, I would also disagree with
> > somewhat. I think it probably depends on the gouache, but I'm told that
> > if you dilute some artist line gouaches down enough, they will behave
> > like transparent watercolor and give a transparent effect that you
> > wouldn't be able to distinguish from a transparent watercolor of the
> > same color. I was told by Arthur Graham that this is true of the M.
> > Graham gouaches. I hate to disagree with someone who obviously knows his
> > own paints, but I think that's probably only true when painting on white
> > paper, that you can't tell the difference between them. Over a dark
> > background, if you compare a transparent light-valued pigment in
> > watercolor paint to the same pigment in gouache, even at a very low
> > concentration the gouache pigment will be visible as a light veil of
> > color over the dark background, whereas the same transparent pigment in
> > transparent watercolor will disappear against the dark background.
> >
> > Gotta go, more on this later,
> > Katharine
> >
> >
Received on Tue Jan 18 16:13:19 2005