IC Riso Printing – Page 2

Registration & Trapping

The Risograph has limits of accuracy. Each color layer requires a separate pass through the printer, registration on multi-color Risograph prints will never be perfect.

It is recommended that you add registration marks to your image to aid in lining up multiple layers. These can also double as trim marks if you plan on cutting down your print to size.

Line work printed over solid blocks of color will usually look best.

Registration (aligning overlapping colors) can be tricky and often imperfect on the Risograph.

When colors are misaligned (misregistration), you can be left with a glaring white gap that can detract from your overall piece.

Trapping is a remedy to misregistration. Trapping is the practice of adding a little bit of overlap between adjacent colors to make sure that there are no white gaps between them even when registration is a little uneven. In other words, trapping expands pixels where color channels touch or overlap.

Trapping channels in Photoshop

Select all channels you want to trap.

Trap
Menu bar > Image > Trap…

Select the number of pixels or millimeters you want to trap. (We recommend you do the highest allowable.)

There will only be a slight visual difference in your file, but this will help your colors overlap once you print.

Click OK.

Risograph Image Options

The Risograph can print at 600 d.p.i. and has two gradient techniques to choose from:

Grain Touch: a randomized diffusion dither pattern (like a photo or film grain)
Screen-Covered: creates classic halftone patterns on a very small scale.
- Screen Frequency controls the size of dots produced (higher numbers = smaller dots).
- Screen Angle controls the angle that the pattern is set to.

We recommend using Grain Touch over Screen-covered. If you have questions about screen-covered and Riso halftones, please contact the IC.

Opacities & Overlap

Use opacities and overprinting, or overlapping colors, to create new values and hues.

The RISO will print these colors one at a time:

Opacity does not work the same way as grayscale. Take the pink towel for example. In order for a color to print 100% pink, your plate must be 100% black.

Understanding Color Separations

The Risograph prints one color at a time, which means your piece needs to be separated into pages by color:

Riso Printing | How does the Risograph Work?

An image is either sent digitally from the Riso PC or from a physical original via the scanner bed. The master is created by burning the image onto the master roll inside the printer. This stencil is then wrapped around the ink drum. The Riso feeds paper under the ink drum as it rotates, and ink is pushed out through the stencil to create an impression.

On our Riso, two colors are printed at a time, and multicolored prints are made by switching out drums, then printing over each layer. The paper passes through the machine multiple times.

Risograph ink is translucent, so its final appearance depends on the color of the paper it is printed on and the layering of each ink. Colors can be overprinted to create new ones. It’s also possible to blend any combination of tints of color together to produce color variants.

Ways to participate in CCS Riso

Trained students can rent time in the Riso Room year-round. The IC hosts Riso Printing events during the school year and student organizations (e.g. Riso Club, Freeform Press) use the Risograph for club events.

A brief explanation of how a Risograph printer works. Along with an introduction of the Risograph Studio in the Imaging Center.