Re: Gum problem(s)

From: Katharine Thayer ^lt;>
Date: 11/20/05-11:18:11 AM Z
Message-id: <>

On Nov 19, 2005, at 3:13 PM, Judy Seigel wrote:

> Not sure if I'm "the one" Katharine refers to, but 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?

I think the difference in how we read this and find it useful or not
useful has to do with differences in background and culture. This is a
scientific literature review, and is intended to be read as a
literature review, a summary of the evidence about a particular topic
that was available at the time the review was written. The review is
just a quick way of getting a fast picture of where the science is or
was at a particular point in time, without having to read all the
original sources first to get there. Since Kosar's point in time was
1965, it doesn't make sense to read it as current state of the art for
dichromated colloids. (A more current literature review,
unfortunately has not yet been written).

If you're interested in a particular finding cited in a literature
review, you go to the original source and read that, rather than taking
the word of the reviewer about it; besides usually in a literature
review each finding each gets only a sentence or a half-sentence, and
it's difficult to present the whole of a ten-page study, say, in one
sentence. You read the original source and evaluate the methodology,
the results, and the conclusions and draw your own conclusions about
the possible validity of the findings. But the only way to know for
sure whether you agree with them is to do the research yourself, in
other words to attempt to replicate the study. ( I did in fact, a
couple of years ago, read a substantial number of the 170 original
studies cited in Kosar's chapter, and with the help of a chemist
colleague have undertaken to replicate a couple of them).

Evidence "suggests" or "indicates" but never *proves* anything, and is
simply confirmed or disconfirmed by subsequent evidence. That's the
way scientists talk, that's the way they think, that's the way they
work. The more confirming observations pile up, the stronger becomes
the finding. The more disconfirming observations pile up, the weaker
becomes the finding.

I would read the entire section "photochemical hardening of dichromated
layers" with the understanding that this is a historical document and
doesn't reflect current understanding of what happens. It's useful to
know the history of how people's thinking has gone on this., but I
certainly wouldn't present as fact, for example, something Eder said in
1878, just because it's cited in Kosar.

What made Kosar worth driving six hours for (I only paid $25 for mine)
was that when I was done reading it the first time, I understood that
the questions I had about the process hadn't been answered yet, at
least in 1965, and that was interesting, even exciting to me, and is
still interesting and exciting.

> Secondly, and much more worse, I didn't find any of it I can apply to
> gum. The tests were all (as stated, and that I came across, tho I
> admit only checking the seemingly relevant chapters) applied to CARBON
> printing, or a derivative of carbon. Not gum. And no matter what they
> tell you, just because it's dichromate does NOT mean they're the same.

I agree with you that it's a crying shame that there's almost no
research on dichromated gum itself, but that's one of the hard facts of
our existence. In the meantime, if we want to get a clue about it, we
have to get a glimpse at it indirectly, through either dichromated
gelatin, or (more usefully, I think) dichromated PVA. I suggest
reading Kosar only as a way of peeking at an angle; I certainly
wouldn't recommend taking all or any of it as literal truth. Kind of
like how I'd recommend reading a religious text, I guess. Useful for
getting an idea about a way of looking at the world, but II certainly
would never cite a finding about dichromated gelatin as if applied by
definition to gum, and in fact didn't cite the relationship between
humidty and sensitivity until I had seen it confirmed in dichromated

I feel kind of helpless here, like I'm talking to someone who speaks a
different language and there's no way to communicate but with hand
gestures or something. Anyway I've got a breakfast date and should get
Received on Sun Nov 20 11:19:08 2005

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