Tacky attraction< (was Solarplate images...website)

[SusanV <susanvoss3@gmail.com>]

So the leprositic measles we're getting in our gravure prints may be
from the tackiness of the KM73 plate surface against the inked side of
the OHP film.  Talcum powder helped but didn't solve my problem.  So
now I wonder how we combat this tacky issue?

We need to allow the trapped air to move to the outside edge of the
plate/ohp sandwich, so the vacuum can pull it out.

I'm just brainstorming here...

corn starch (maybe it's better in some way than powders which have
other additives)

some wet type of lubricant?  can't use water of course, but what about
oil?  would a light oil film dissolve the inkjet ink?  Would it wash
off the polymer plate easily during development?  I could imagine
using a brayer to bring the ohp in firm contact with the plate before
exposing... working from the inside out to push air pockets to the
edges.

Using the brayer idea through Krene plastic during drawdown to help
push the air bubbles to the edges of the plate where they could
escape.

is there some type of thin film we could add to the sandwich, in the
middle... nah, that sounds like a newton ring nightmare...

one more thing... what if we expose the positive with the printed side
UP away from the plate?  Is the opposite side of the ohp as tacky?
Would it make an unacceptable difference in image sharpness?

susan, frustrated.




On 2/26/07, SusanV <susanvoss3@gmail.com> wrote:
> Hi Jon and Chris and all,
>
> Update regarding measles:
>
> Today I was exposing an 8x8" plate (image exposure), and very clearly
> saw the leprosy you describe during drawdown.  I had dusted the plate
> with powder but if that helped it didn't do enough.
>
> I removed the plate and positive from the vacuum bed, and tried
> dusting powder on the emulsion side of the positive.  It was harder to
> brush off and was leaving streaks, so I used a new microfiber cloth I
> use in the darkroom, which worked well.  BUT... the leprosy happened
> again.
>
> My vacuum bed has a typical bumpy surface, but I have a smooth white
> sheet of plastic over the center area.  I noticed that the plastic
> lifted up against the glass all around the plate and positive during
> drawdown, and realized that using the plastic possibly circumvents the
> design of the pebbled surface, which must be to allow air to flow
> through all those little channels between the bumps.  So, I removed
> the plastic and tried again.  Initially got the same result, but then
> let the drawdown continue for a minute or so, and it did seem to
> improve.
>
> By the way... I tried different drawdown times, and the spots got
> smaller with longer times.
>
> I eventually just let it draw down a couple of minutes, then made my
> exposure, even though I could still see some spots.  I've pulled 2
> plates, and used paper that had soaked overnight, but still got some
> small measles.  The splotches are small and fairly regular and evenly
> distributed, and mostly in the mid-tones.  I'll scan it in the morning
> after it dries and post it to my blog.
>
> I'm still using the glass on my Nuarc... maybe tomorrow I'll build the
> frame for the krene plastic and switch to that.  I was just impatient
> today and wanted to print.
>
> Susan
>
>
> On 2/20/07, Jon Lybrook <jon@terabear.com> wrote:
>
> "Susan:  If you want to test this, take a virgin KM73 plate with the
> mylar removed, and a virgin piece of OHP (without an image printed on
> it), sandwich them under the vacuum frame and hit the switch on the
> vacuum.   I'll bet you see a similar, but subtle pattern of patches
> manifesting like leprosy within the first minute of drawdown.  The
> aquatint screen, unlike your image transparency, is made of real film
> and doesn't have this issue, but the OHP is tackier against the KM73
> plate and this is the problem.  The remedy for me has been baby powder,
> very lightly dusted over plate with a hake brush (Jan gave me the idea
> several years ago).  If you were using baby powder, the other key is to
> not let the image exposure draw down too exceedingly long.  I basically
> wait until the Krene goes flat against the bed, then hit the exposure
> switch with no extra drawdown time beyond that.  Since the screen
> exposure is not the issue, you can draw down on it as long as you want.
>
> --
> susan
> gravure blog at www.susanvossgravures.blogspot.com
> website www.dalyvoss.com
--
susan
gravure blog at www.susanvossgravures.blogspot.com
website www.dalyvoss.com