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Discussion Starter #1
Hi,
I'm new to the forum, and still figuring out things in Illustrator CS5. I need some help with trapping. I've searched the internet, and read several posts here, but can't seem to find what I'm looking for...

I have a three colour design that needs trapping. The design will be silkscreened onto transfers, and printed in reverse order -- black will be the first ink. Then it goes through the dryer, the paper shrinks, and so the next two colours are mis-registered. The screenprinter has asked me to trap the black - so it's thicker/larger than normal, and then will register perfectly when it shrinks down with the paper on the first pass through the dryer.

So I did as suggested in the manual... I think. I selected paths of my black objects whenever they butted up against another colour, increased the stroke size, and clicked "overprint stroke." After saving, I printed separations to a postscript file. When I printed out the separations and held them up to the light - no overprint.

Does anyone have an idea what I might be missing, and/or know of a good tut on the subject, specific to Illustrator?

Thanks!!!
 

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One possibility is the option of how a stroke is oriented in Illustrator. The default (I think) is that the stroke is centered on the path, so that with a 1 point stroke, half the stroke is inside the path and half outside. When you overprint a stroke that way, you end up with a 1/2 point trap.
You also have the option of orienting the stroke to the inside OR the outside of the path. You'll find these options in the 3 "Align Stroke" buttons in the Stroke palette (at least it's that way in CS3). If you'd picked the stroke to be on the inside of the path, overprinting will do nothing.
One other thing is printing seps. Postscript options don't always show up in the final product unless you're using a RIP or a true postscript output device. What are you using to print the postscript files you're generating?
 

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Discussion Starter #6
Thank you for your fast and great replies!

I have now figured out the trapping, and had a good look at it in Overprint Preview mode -- made it easier to check the traps by temporarily changing the black to 50% gray.

As for why the printer doesn't pre-shrink the transfer paper before printing... he says he tried it once a long time ago but without success. Does anyone do this regularly and have it down to a science? If you're printing 50 transfers, do you fan it and then put a pile of 50 through the oven? Do they stay shrunk long enough to print 3 or 4 colours?
 
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