"Speckles" on BFK [was "speckling" v "staining

On Sat, 3 Sep 2005, Christina Z. Anderson wrote:

> My point is that a lot of beginning gummists get this speckle/grainy effect,
> and my guess is, that with a different paper and different size, this would
> not happen.

Absolutely -- although Rives BFK happens to be one of the few papers that
can be used (for one coat anyway) with no added size, and its
characteristic speckles are of a different order entirely from the "grain"
or "tone" or "staining" or "flecks of pigment" from various other causes.

> My guess is, that Rives has little paper fibers that get brushed up and
> extend past the size and don't get enough size, OR glyoxal crystallizes
> gelatin in such a way, that catches and doesn't release pigment. Why the
> latter guess is that my glyoxal coated FAEW hot press also speckled. In
> fact, when I go back through my prints I did over the last 2 years (probably
> about 500?) I can tell the glyoxal from the glut by feel and look.

Again, although I've never noticed it, I see no reason to doubt the
"crystalizing" of gelatin by glyoxal you cite, but the characteristic
"speckling" of BFK can't be from "brushing up" the fibers, problem size,
crystalizing, "catching," not releasing... etc. etc.

Firstly, the characteristic BFK "speckles" are white, not pigment. Then,
the most distinct white "speckling" on BFK is on cyanotype and VDB,
neither of which get added size. That paper is easily and well saturated
very fluid emulsion -- no way it's not fully coated.

Plus, I vat size for gum (not brush size) and still it can appear --
although *much* less than on cyano or VDB, where it's so marked and
troubling to students I warn against BFK for those media, unless they
*want* the effect.

But this explanation seems to fit all: the tufts of paper fiber are
flattened over the paper by the contact frame glass, so that the paper
directly under the tufts is not exposed (no matter how fully saturated).
That would also explain the characteristic shape or outline of BFK's white
spots. (Lacking a microscope, maybe a 10-power loupe?)

INE the white flecks don't happen as much in gum as in cyano, so I
wouldn't guess how or if different sizes would affect it. But here's a
considered guess about why the BFK does less distinct flecking with gum
than cyano: Gum has much more "dot gain", so tiny shapes would be less
sharp. Also, the emulsion being thicker, having more body, sitting partly
on top of the paper besides soaking into it, would have more blurred or
spread optical effect -- or is that the "dot gain"?

> If the topic of glut's toxicity comes up, remember that both formaldehyde and
> glyoxal are very toxic, too. I personally would NOT hang over a tray of
> glyoxal as a hardening afterbath any more than I would hang over a tray of
> glut.

Which brings up the fact that Katharine's experience with glut is
apparently cited here as one of two seriously bad experiences from
listers. Yet, as I recall, after describing a truly harrowing effect,
Katharine posted a day or two later to say that proved to be due to
something else. Then it wasn't the glut?

In my experience, the worst experiences (other than the Zyklon B, or death
camp gas, I accidentally generated by leaving stuff in a covered tray &
then casually lifting the cover a couple of weeks later, my closest photo
near-death experience).... were with formaldehyde... But this was merely
painful odor, burning throat, watering eyes, etc. enough surely to warn to
avoid, etc., but no detectable symptoms of nerve or brain damage. Glyoxal
in the amounts used had almost no detectable odor and NO other noticeable
effects. Not to say there weren't but ....I can go out my front door and
get a whiff of the fumes from the Fresh Direct truck & nearly keel over.

I frankly don't trust any MSDS on glut or anything else -- having read the
MSDS on, for intance, gum arabic powder -- they've GOT to give you
worst-case scenario, raised exponentially because geared to a 40 hour week
of industrial strength exposure.

It would be more useful to know if, for instance, glut is worse then
glyoxal... Or is that unknowable?

And finally, about yellowing from glyoxal -- There seems so far to have
been no case of glyoxal yellowing (except at a bottom drip) when the paper
is rinsed after a glyoxal *bath* rather than glyoxal added to the gelatin.

Is this correct?

Judy
Received on Sun Sep 4 16:14:38 2005