>
> On Fri, 5 Jun 1998, Judy Seigel wrote:
>
> > Dutifully running this test one day with fresh paper, on a whim I tried it
> > on preshrunk paper. Oops, the result was completely different. I
> > understood in a trice that any variable -- length of soak, order of coat,
> > etc. -- would also be completely different. Later it dawned on me that the
> > dichromated emulsion also changes the paper, ...
>
> Not surprising. You've run into a very common misconception about the
> so-called scientific method. Namely that one should only change a single
No Wayde, what I had run into was utter LACK of scientific method. As far
as I can tell, Anderson simply *reasoned* that the way the pigment and the
gum alone did or did not release from the paper would tell you something
useful about the way the pigment would work in an emulsion, that is with
DICHROMATE and EXPOSURE added, but never checked to see if his assumption
was correct.
Leaving aside any other kinds of "variables" -- ratio of pigment, of gum,
of dichromate, etc.-- he was out of it at the outset. Every single one of
the gum pigment ratio tests was irrelevant, meaningless, beside the
point, and useless, however many variables he did or did not change at
one time or in a schemed manner.
Another issue that I didn't get into in my overly long post about the
"Ansel Adams" gum chapter was the assumption that there CAN be an "ideal"
emulsion. It totally depends on everything else, such as which layer
you're doing, one of many, or a single, what you want it to do, how you're
going to develop it and what's under it -- not to mention one of the most
important variables of all, namely what paper you're putting it on.
Different sizes and textures of paper take emulsion differently.
> and that you choose to test only two values of each of these 5 variables.
> You would have to run 32 tests to get a complete data set. Adding a sixth
> variable increases this to 64 separate tests! If you allow for more than
> two possible values for each variable the numbers get even bigger. It
> doesn't take long before one simply can't perform all of the experiments
> needed. The solution to this dilemma is through statitical experimental
> design where several variables are changed simultaneously. Experimental
> design is a dicipline in itself so I'll quit while I'm ahead here.
Unh unh.... I say right out in public that for gum I find the notion of
statistical experimental design, which I have equally failed to understand
elsewhere, dubious at best. In fact maybe that's the kind of thinking led
Anderson into the morass he got himself into -- he *thought* he was doing
that with the gum-pigment ratio test. (I'm just kidding here, Wayde, I'm
sure the fact that just because mego in my attempts to divine such systems
doesn't mean they aren't wonderful and important.)
Meanwhile, non-science, Anderson's myths of gum printing, never die, as we
see...
cheers,
Judy