Re: solarplate wedgies
Jeremy and all,
I'm pretty sure they are newton's rings.
When the moisture gets trapped it keeps the two surfaces from meeting
firmly, and THAT is what causes the Newton's rings. Not exactly the
moisture, but the space created by the moisture. As it changes to
vapor and expands. The space between is what causes rings.
AND another thing about ohp and polymer... I believe the tackiness of
the polymer surface "grabs" the coated surface of the ohp and seals
off bubbles, if you will, of air that become trapped. Like smoothing
wallpaper bubbles... the vacuum can't get all the air out. That's why
powder helps, or a roughened surface. That allows the air a route of
escape to the edges of the plate. We've talked about this before, but
just for anyone who missed it.
On 4/6/07, Jeremy Moore <firstname.lastname@example.org> wrote:
I see the interference patterns (I hesitate to call them Newton Rings as I
think they are related to moisture) immediately upon forming a vacuum in my
Nu-Arc, i.e. no time for venting from the paper.
On 4/6/07, Barry Kleider <email@example.com> wrote:
> This might/might not be helpful -- I don't pretend to know anything
> about PD printing....
> Are you sure it's the film which is causing the moisture/condensation?
> I've been doing some cyanotype prints over the past year, and several
> times I've seen this condensation under the glass.
> I've assumed the problem is caused by moisture in the paper "venting"
> out as the paper warms up in the sun.
> Katharine Thayer wrote:
> > On Apr 3, 2007, at 11:37 AM, firstname.lastname@example.org wrote:
> >> I noticed the problem when printing palladium from diginegs on the new
> >> 'improved' Pictorico Ultra. The back (non-inked) side was giving me
> >> some
> >> interference patterns that would occasionally be noticeable in
> >> smoother
> >> toned areas of my prints. The old stuff did not do this.
> > I've had the same problem once or twice with the inkjet film I use,
> > which I buy from filmsource and so don't have a specific name for.
> > When I did have the problem, it was connected to printing before the
> > film had dried enough after printing. Not the ink, but the film
> > itself. The film isn't dry enough, or maybe that it's not cool
> > enough, and the warmth causes condensation of the glass; at any rate
> > there's moisture that caused this Newton ring-like thing (but not
> > the usual Newton rings, which isn't a function of moisture) between
> > the back of the negative and the glass. I found that a combination
> > of drying the back of the negative with a blow-dryer and adding a
> > puff of talc (I do it the same way Judy does, with a puff bottle. A
> > little poof of talc upward, let it settle, and that's all you need)
> > took care of the problem.
> > Katharine
gravure blog at www.susanvossgravures.blogspot.com