Registration

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Media Location & Registration for Printing-


In order to print multiple colors precisely, some method of accurately placing media must be employed.  Two techniques outlined here are taped corner registration and pin registration.  With some work there is no need for super accurate registration.  For example, with the Drawing ink and Filler example the registration used was very loose so taped corners did quite well.  With a process color (CMYK) print registration is imperative. Since colors are "mixed" in the eye, a small bit of misalignment between screens / colors causes large changes in the final look.

Taped Corners-

Taped corner registration is quick and cheap.  It consists of, you guessed it, tape markers on diagonal corners of the print media.
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Using this system does take a little extra attention in placing each new sheet of paper but beyond that, it's an effective method.  With the work surface prepared with tack spray the media should stay put where it was placed.

Pin Registration-

Another, more technical, method of registration is to use pin registration.  When using registration bars, the paper is stacked and placed in a specialized hole punch.


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The self-centering punch leaves holes in one edge of the paper that match a sheet metal strip with pins secured to it.  The registration bar is then simply taped to the work surface and paper place over the pins.


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 That the paper punch and registration pins are a system, there can be very tight tolerances and very accurate registration is then possible.  An alternative to the pin registration system above could be to use a common three hole paper punch and individual pins.




Many three hole punches yield 9/32" holes - a near-perfect fit for the 1/4" pins on the single pin registration units.  Do make certain that the punch will process many pieces of paper in one operation.  If the punch only punches holes in three pages at a time, only three pages will have the holes in the exact same location.  This will introduce more potential for error in your prints.

Lining up the Screens-

Getting the desired registration, at this level, is still a matter of lining things up by eye.  This can be done by placing a dry test print under the next color screen to print and visually moving the paper to match.  If the masking on the screen is too opaque to see through, a print can be made on an acetate "page" that is taped to the work surface along one edge.  Use the acetate print to line up the target media and flip the registration image out of the way, like a page in a book, when it's not needed.  For pin location, line up the next color and tape the registration pins to the work surface.  The pins will manage alignment for subsequent prints of the current color.  Each time a new color or new screen is needed the registration process will need to be repeated.

Registration Marks-

If preparing screens digitally registration marks can be added during the creation of the master. Registration marks are an accurate way to perform registration to very close tolerances and are best used with highly accurate location systems such as registration pins.

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If your graphics application does not have registration marks built in simply add them into the edges of your artwork, making certain they are present and accurately located on each layer of your digital master.  Print them with each screen and burn them in along with the image at exposure time.

 Trapping-

Perfect registration is tough to achieve, even more true when access to specialized equipment is limited.  An acceptable way to hedge success is to allow some purposeful overlap of colors.  A print with an unprinted strip between colors is much more noticeable than where colors overlap. Trapping can also be used to introduce an additional color into the print when transparent inks are used.  Some of the examples below show an outline effect that was created with trapping.

Trapping Page @ wikipedia 


Trapping can be added at the digital stage or added to laser print masters with a Sharpie marker after they're printed off the laser printer.  If trapping is to be used, make certain it's on the master before the screen is burned.  If it's not included before the burn, it's too late!  Give a little overlap, your prints will look better for it!



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