9488Re: platemaking issues
- Mar 12, 2008--- In PPLetterpress@yahoogroups.com, typetom@... wrote:
>Tom, the vacuum frames made by NuArc that are designed specifically
> (I'm not clear what you mean by: "Proper use of relief valve will
> leave no air between glass, neg, and plate, and full vacuum is
> indicated by appearance of Newton's Rings." I'm not aware of a
> "relief valve" in my system.
for platemaking (fliptops, 26-1K etc.) have a relief valve or bleed
valve. You leave it open until the blanket is pulled up to the glass,
then slowly close it. That slower draw allows all the air to be
removed without any remaining pockets.
The NuArc contact frames designed for general contact printing
(with no integral light source) don't have the relief valve in the
stock vacuum system, which draws down in a few seconds. I suppose
that's because only a few layers of film were normally placed in the
contact unit, while the platemaker might have to support heavier
contents such as a step-and-repeat board.
Other than the valve, the frames function identically. It wouldn't
be hard to add a valve, just cut the hose leading to the frame and
insert a needle valve the appropriate size. It might simplify your
process, if I'm right. But cardboard is cheap, and if a system works,
--Eric Holub, SF
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