About testing (long) (was: Re: The consistency of gum)

I'm trying to limit my reading of the list and don't ask me why this is
the post I picked to read this morning, but there is a question for me
here which deserves an answer. I thought about it for a while and
decided I want to say something about testing in a more general way,
rather than answering the specific question, or at least if I answer the
question it will be in the context of this bigger thought:

Judy wrote:

"However, I'm curious about the finding stated below that the
powder-made
gums have a longer scale. Can you state some numbers for comparison? Is
it possible it's not the powder vs. the pre-mixed *per se*, but the fact
that the % or some other attribute is different?"

I read this and thought, how in the world did we get here, how in the
world did *I* get here, to this place?

To anyone who just came on the list five days ago or so, it will
probably come as a huge surprise when I say that I'm not a person who
does much testing around gum printing, except when it's necessary for my
own work. When I needed to change papers, then I tried out a lot of
papers to find one that was smooth enough to show the subtle tonal
gradations I wanted to express (and I'm still looking, by the way,
because the Fabriano Uno I settled on in the press of deadlines has
never suited me very well). And now I'm testing gums because I need to
change gums.

These tests are for my own use and weren't intended to be published or
to be taken as general rules for gum printers of the world. I don't do
testing in search of the "truth" about gum printing, for two reasons:
(1) in some parts of my life, I'm very intellectual. In making art, I'm
not intellectual at all, beyond the analytical process necessary to
develop the craft. I just want to make pictures. So I'm not interested
in spending my time running tests.

But much more importantly, (2) trying to do that kind of testing seems
like a fool's errand to me. No doubt my attitude in (1) enters into this
as well, but the main thing is that as a statistician, I can't see any
way that one person could get results that would be generalizable or
useful to anyone else. There are too many variables that differ too
much among us. A person would have to have a huge lab with every
conceivable type of light, you'd have to.....well, you get the picture,
I think. The task would be beyond one person's grasp; it would require a
whole lab with assistants and everything, and it would take years to
come out with definitive answers. And by that time, all the gums would
have changed anyway, and you'd have to start over. Like I said, a right
fool's errand, in my opinion.

When I came onto this list five years ago, I had long since developed
the printing method I still use, and had been showing my work in
galleries for several years. But that meant nothing to the people here;
their test results proved that I was using the wrong gum, and that was
that. Luckily I had enough sense to believe my prints over their test
results, and I proceeded as before, with my "inferior" gum. The point
of telling this story for the nth time is to say that there is no way
that I want to get into the business of telling people what gum they
should use.

The requirements for proving something in a positive sense (x gum prints
the most steps, for example) are much greater than the requirements for
proving that an assertion is false. Finding a thousand white swans, to
use Karl Popper's example, (that was Karl Popper, wasn't it?) doesn't
prove the proposition that all swans are white, but finding one black
swan disproves it in a second. My purpose in posting to the list for the
last five years has been to point out the black swan whenever someone
says all the swans are white. Unfortunately there are a lot of people
making categorical statements about gum printing, and the majority of
them are wrong, so I've had my work cut out for me.

I figured out last night what might prompt someone to say that I have an
agenda, that I'm trying to protect a particular "turf." The only black
swans I can point to are the ones I know about, by definition. If
someone says that saturated ammonium dichromate can only print a low
contrast print, I can say confidently that it's not true, because I
know quite a lot about printing with saturated ammonium dichromate, and
I know from solid experience that it's not true. When it's considered
"protecting turf" to provide information about something that one knows
quite a lot about, then we're all in deep trouble.

I got to this place by providing data to counter something I thought
someone said. From there I somehow got tangled up in Sandy's mission to
find out how much gum is in gum. In discussing that question, I said I'm
finding gums rather similar, and then for clarification I made the
distinction between pure gum acacia and whatever that black guck is. To
make the point, I cited some of my testing data to show that the one
sample of black stuff I'm testing not only looks different, but acts
different from the other gums. And I'm afraid in the excitement of the
moment I got carried away and sounded like I was making a general
pronouncement about how that black gum prints. This is not what I want
to do.

With all that in mind, I'll answer the question. In MY studio, with MY
light, with a few kinds of paper, with only one pigment mix (very
important!), in repeated tests, the Daniel Smith standard gum available
now from Daniel Smith, consistently prints 5 or 6 rather
widely-separated steps, whereas the other gums consistently print from 7
and up more smoothly gradated steps. Two of them seem to be printing ten
steps, but that's so hard to believe that I'm not believing it yet, and
I'm NOT going to say which gums they are. And I will NOT choose a gum on
the basis of these tests. I ran the test out of curiosity to see how
they compare on a strict comparison, but the way I will pick a gum is by
printing with each gum for a time, using all different kinds of
negatives, all different pigments, etc, and seeing how I like printing
with it, how it prints the tonal gradations I want, in practice. So far
the only gum I've spent some time with is the Daniel Smith premium gum,
and I really like the way it prints, but since I haven't printed a lot
with the others, I can't say which one I'll end up with. The point being
that tests aren't the final answer to anything.

As to premixed vs powder, that's not the distinction I'm making. All the
gums I'm using came to me premixed. I'm distinguishing between pure high
quality gum acacia mixed with nothing but water and a preservative, and
whatever that other stuff is, that is full of sediment and doesn't dry
in the bottom of the vial to a hard transparent amber disk if left
overnight but stays a gummy black mess that is a royal pain to dig out
of the bottom of the vial. That's the distinction I'm making.

But the bigger point is that while this information may be interesting
from the point of adding data to the stream, it should not be taken as
an endorsement or condemnation of any particular gum in a general sense.

When I posted the thing about the Formulary gum, it was only because
someone had asked me recently what gum I used, and I had answered, so I
thought I should let people know that the gum I was talking about is no
longer available. I shouldn't have added that I don't recommend the new
Formulary gum, because obviously people like that gum or they wouldn't
keep carrying it. What I should have said, and what I said later, and
what is more consistent with my philosophy, is that I don't particularly
like the gum that they're selling now, but that's just me, and I
wouldn't want to influence anyone else's choice.

Sam (the man smiling in the corner) has got the right idea: just do it
and don't talk about it. I have long believed that gum printing can't be
taught but must be learned through experience, I've never tried to
teach anyone how to print gum, although I have answered questions when
asked, and I've tried to counter misinformation when I see it. But in
the end, nothing that's said here is going to help anyone learn how to
print gum; the only way you can learn how to print gum is by printing
gum. So we should probably all go off and print gum. My 17cents worth.
Katharine Thayer
Received on Wed Dec 3 14:13:40 2003