Re: Gum problem(s)

> On Nov 19, 2005, at 3:13 PM, Judy Seigel wrote:
>
>> .... I've been more annoyed
>> than pleased by Kosar. For two reasons, firstly, NONE of it that I recall
>> is his own testing, it's all "so and so" claims that thus and thus "seems
>> likely" or "probably therefore" or "indicates," "suggests," or "we thus
>> conclude" and so forth. In other words at best it's a surmise at one
>> remove... and don't we know better by now than to trust "tests" IN ANY
>> MEDIUM where all variables are not controlled -- and all materials from the
>> same source?

On Sun, 20 Nov 2005, Katharine Thayer wrote:

> I knew there was one more thing I wanted to say: Since the information in
> Kosar is taken from 170 different sources, this last sentence above makes no
> sense.
> kt

I don't think my meaning is very obscure, but let me rephrase: If MY
process doesn't act like Kosar's experimenters' process acts (even if any
of them were doing gum), I have no way of knowing whether it's because our
materials are from different sources (as they are of course bound to be)
or our equipment (say, light source) is different, or because the
description is incomplete, the variables not fully expressed, or not
understood, etc. etc. etc. Which is to say -- and surely we know this from
discrepancy in findings mentioned here -- the phenomena they examine may
have been meaningful for "science" or for commercial purposes, but struck
me as less useful to *me* than observing a classroom.

Now Katharine seems to say Kosar is valuable mainly for orientation in the
*history* of the medium at that point in time. That wasn't the position
of whoever it was back in the day citing Kosar as *the* ultimate
authority...

I doubt I found one thing of practical value... As for broadening oneself
by acquiring this other info, I already have too much info. What I don't
have is enough TIME -- there's always more to read than I can get through.
So time spent with Kosar was more or less wasted. Better to have spent the
equivalent on, for instance, my own tests, which ALWAYS give information,
if only to show what ELSE to test.

I suppose I'm glad to have poked through Kosar just to know I'm not
missing some great revelation (and mine only cost $15 at A Photographer's
Place), but -- Chris, I did some of those tests from your top 10. Did
you? I found, I'd say, about 25% correlation of effect. For instance the
addition of ammonia to an emulsion had a limited preservation effect with
some mixes, tho just for a 24-hour window of time. Big deal... the way I
mix emulsion is so simple it makes more sense to keep my variables
constant, that is, to mix at printing.

The part about the magnesium (was it?) sulfate was of course not true.

As for the business about PH and print speed --Chris, did you test that?
I have noticed (& mentioned on the list) that my several gums have
different speeds (a variable which has its uses). Some by a factor of
three !!! I measured the baume at Pratt's chem lab. (A very old crystal
and silver hygrometer, or whatever the name. I didn't steal it, but lusted
after it.)

All were the same baume. I measured the PH, they were different. but the
pH did NOT correlate with the speed. I figure, FWIW, that the speed could
be related to the preservative used in these different commercial gums, or
possibly the particularities of the acacia trees, their age, or soil, or
whatever. It's true I didn't test the pH of the dichromate alone -- but
my tests showed PH wasn't going to be a key to anything.

Etc.

One other note about the pigments, under discussion -- as I recall, Daniel
Smith WC is much less expensive than Winsor Newton... At least in the US.

Judy
Received on Tue Nov 22 00:57:10 2005