Re: Dots of gum?

On Fri, 18 Feb 2005, Katharine Thayer wrote:

> Well, this would all make sense except for one problem: it seems to rest
> on an assumption that a continuous tone negative doesn't print as well
> in gum as a negative made of dots, which I would have to dispute on the
> basis of my own experience.

I'm in a state currently where I have trouble remembering this morning,
let alone what I said last week (not senility, I believe, just overload),
but I think this has been taken a step further than my meaning. (And note
my final, "If the premise is true.")

I didn't mean to say that "a continuous tone negative doesn't print as
well" as a dot negative, although "well" would also depend on the
variables of original, exposure, intention, formula, substrate, etc. etc.
Certainly most of my gum experience has been exactly with continuous tone
negatives, and I thought they printed quite nicely, thank you -- once I
learned a thing or three (thanks to the 21-step) and did about 100000 size
and hardening and paper and pigment tests.

My *recollection* is that the subject from which these points grew was
getting gum emulsion to stick to a hard slick surface.... thus my surmise
that that would be *easier* with a dot negative, for the reasons stated.
But since the subject is on the table -- for SURE, it's easier to print on
paper with a continuous tone neg than on glass with heaven's most perfect
dot.

I would guess furthermore that the only way to determine such (possibly
theoretical) "better negative" across the board would be by ACTUAL TEST.
And given the different findings we all find (I mean imagine Don Bryant
finding that heat-drying cyano blotches LESS, or Katharine finding that
she can print without a gelatin size and not get pigment stain), that's
probably useless.

On the 3rd (4th?) hand, aren't some dot screens configured in squares,
pyramids, triangles, whatever, so everything (image and surround) has, if
not the same shape, the same straight edge? Then, who was it added that
the really killer dots have softened edges? -- which might in a way mimic
the "softness" of continuous tone...?

Had enough?

PS. But thanks for the prize.

Judy

>> I don't think the issue is whether you're printing "dots" or their
>> surround. That is, it's not the *shape*; it's the construction. A contone
>> negative has unequal density (for the highlights or shadows depending on
>> whether positive or a negative) that gets fainter and fainter until some
>> of the marks are thin and light. That is, more "off" than "on," plus lots
>> of inbetween. The fainter marks are less exposed, less substantial, than
>> fully exposed, and their emulsion therefore more easily washed away.
>>
>> In a halftone negative, there are no such inbetweens. Everything that's
>> supposed to be exposed is full bore; the edges, whether of the surround or
>> the dot, are clear cut -- either "on" or "off," thus the partial tones
>> don't handle differently (or not very differently) than full tones. In
>> some (all?) halftones the thinner tones get smaller dots (or, as I recall,
>> used to anyway), so that may affect printing, tho that's probably a
>> footnote, not this question.
>>
>> That's my theory, anyway; if the premise is true, it's probably along
>> these lines.
>>
>> Judy
>
Received on Mon Feb 21 12:11:43 2005