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

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.

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

If we are talking about painting, then there are some physical difference
too, like the gum in gouache is less than gum in watercolor because
watercolor is expected to be diluted much more than gouache is, so if we
dilute gouache to the strength of watercolor, the brushability feels
slightly different; but that difference is not affecting much when used in
gum.

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.

Dave

----- 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 14:57:11 2005