From: Kris Erickson (kerickso@acs.ryerson.ca)
Date: 02/28/02-10:18:19 AM Z
For silk screen you need either black or white--no intermediate grays.
Otherwise, when trying to expose the mask onto the screen, the 'gray' areas
will not receive enough exposure, and will wash out (likely just where you
want them most). More ink than you/she want will come through the screen
upon inking.
The solution is to create a half tone screen (where the 'grey tones' are
made up of varying sizes of black dots and white spaces--see any news paper
photograph with a magnifying glass to see the effect: those dots are not
grey ink but black ink with varying amounts of surrounding whitespace. It's
an optical illusion from far enough away--the illusion of a continuous tone
image).
In Photoshop the halftone screen can be created by converting your image
immediately before printing to a bitmap (Image>Mode>Bitmap) specifying 50%
threshold. Essentially, this will convert everything light enough to white,
and everything else to little pixels of black. When you print this out, you
will get a decent rendition of your image, and all the tones will be made
up
of solid black pixels. You should play around with the grey point (Ctrl-L)
or the colour curves (Ctrl-B) if you want to fine tune the way the
black&white image comes out; but of course this requires tweaking before
you
convert to the 50% threshold bitmap ;-)
Just a suggestion (from a friend of mine): if you are going to output onto
acetate, make two copies and sandwich them together--this will ensure that
you get solid black densities (i.e. no light leaking through). Sometimes
some printers will not print very solid blacks onto acetate, so you will
need to compensate.
Hope this helps!
Kris
> ----- Original Message -----
> From: "Bill Collins" <photo@intrex.net>
> To: <alt-photo-process-l@skyway.usask.ca>
> Sent: Thursday, February 28, 2002 10:42 AM
> Subject: Silk Screen
>
>
> > My wife wants to start using the computer to make negatives for silk
> screening. Has anyone done this? I don't even know if the process is
> continuous tone (thus requiring negatives similar to those used for alt
> printing), or more of a lith film type response (where some variation in
> negative density can be tolerated)
> >
> > I'm aware of the many posts on using inkjet printers (and every other
type
> of printer ever made!) for making alt negatives and can check the archives
> is that's really required for silkscreen, but I'm hoping its a simpler
> process!
> >
> > Bill
>
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