From: Dave Rose (cactuscowboy@attbi.com)
Date: 02/07/03-10:39:03 PM Z
It's OK to consider "the physics involved" but in actual practice it's much
easier to simply tape a sheet of polyester over the vacuum frame, shove the
negative/paper underneath, turn on the vacuum and expose. The clear
polyester I use does not significantly alter exposure times - certainly no
more than glass would. At 1.5 to 4 minutes per exposure, the "extra layer
in the light path" is inconsequential. I feel obliged to mention again that
dust is not a problem. I'm using a product ("Kleerbase" anti static
polyester) that's designed for high volume and high quality pre-press
applications.
I'm using negatives from 4x5" to 16x20". A "standard skirt of plastic" is a
novel idea but would be very cumbersome and quite unnecessary under my
working conditions. Am I the only person on this list actually using a
homemade vacuum easel with a polyester oversheet? If so, trust me. It
works.
Best regards,
Dave in Wyoming
----- Original Message -----
From: "Jack Brubaker" <jack@jackbrubaker.com>
To: <alt-photo-process-l@sask.usask.ca>
Sent: Friday, February 07, 2003 12:05 PM
Subject: Re: Homemade vacuum easel
> Considering the physics involved here the negative being just as good a
> block of air flow as the poyester the limiting factor is how many feet of
> edge needs to be sealed. With a continueous poly sheet over the neg there
is
> one perimiter to seal. With the neg acting as its own vacuum skin one must
> seal both the perimeter around the paper and the perimeter around the neg.
> Twice as many feet (roughly) of open edge. If it was important one could
> have a standard skirt of plastic that was taped (continueous around the
neg)
> to the neg. It would then act the same as the neg-poly backing sandwich
> without the extra layer in the light path.
>
> Jack
>
> > From: Dave Rose <cactuscowboy@attbi.com>
> > Reply-To: alt-photo-process-l@skyway.usask.ca
> > Date: Fri, 07 Feb 2003 10:55:30 -0700
> > To: alt-photo-process-l@skyway.usask.ca
> > Subject: Re: Homemade vacuum easel
> >
> > No, because the polyester must press against the negative/paper to
ensure
> > intimate contact between them.
> >
> > As far as I can tell, the polyester does not degrade the quality of
light or
> > resultant print quality. Dust on the polyester is not a serious
problem.
> > I've seen no apparent difference between prints made on my vacuum easel
and
> > those made in a conventional glass contact frame. It should be noted
that a
> > vacuum easel is much better for making large prints. Achieving uniform,
> > intimate contact between (large) negative and paper is more difficult
using
> > spring-loaded glass contact frames.
> >
> > Dave in Wyoming
> >
> > ----- Original Message -----
> > From: <Ender100@aol.com>
> > To: <alt-photo-process-l@sask.usask.ca>
> > Sent: Friday, February 07, 2003 9:07 AM
> > Subject: Re: Homemade vacuum easel
> >
> >
> >> would there be a method where you could use the polyester just over the
> > holes
> >> that aren't covered by the negative and paper? Say by using four
strips
> > of
> >> polyester? That way the polyester would not affect the image or
provide
> >> another layer to trap dust? Or maybe it doesn't matter.
> >>
> >> Mark Nelson
> >> In a message dated 2/7/03 10:54:08 AM, cactuscowboy@attbi.com writes:
> >>
> >> << To use, place the negative & paper underneath the polyester and turn
on
> > the
> >>
> >> vacuum. The polyester will be drawn tightly against the pegboard,
> > providing
> >>
> >> excellent contact between negative and paper. Bring the vacuum easel
to
> > the
> >>
> >> light source and make the exposure. >>
> >>
> >>
> >
>
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