Re: Opacity vs transparency (Was: Re: pigment for gum )

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From: Katharine Thayer (kthayer@pacifier.com)
Date: 09/12/03-10:47:06 AM Z


Yu rei wrote:
)
>
> But why doesn't the vector...
>
> "denoting darkness or lightness of value, which is also
> variously called "density" or DMax."
>
> ever become so dark or dense, that it becomes Opaque?
>
> It just seems like if a transparent color's dmax or
> density or darkness gets high enough, it should get to a
> point where so little light could pass, it could not be
> called "transparent" any longer.

If you took the paint right from the tube and spread it on paper, say
1/8" thick, you might well achieve the level of opacity that would stop
light from going through. But then it's not about tonal value but about
sheer mass of paint blocking the light. And at any rate this example has
nothing to do with gum printing in practice. By the time you've added
the gum that's necessary for the gum printing process (the pigment must
be held in a certain amount of hardened gum to create the image) and
spread it in a layer of the correct thickness to print, (a very heavy
layer of gum-pigment will simply flake or slough off in development) a
transparent paint is going to remain transparent at even a heavy enough
pigment concentration to create a very dark value. In other words,
within the normal application range, either in gum printing or in
transparent watercolor painting, transparent paint remains transparent
from light to dark; that's why they call it transparent paint. People
who prefer opacity to transparency will paint or print with gouache or
with opaque watercolor pigments, rather than with transparent watercolor
paint. I keep coming back to where I started; this time I'm getting off.
Bye,
kt


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